Such bearing units are usually preloaded so as to ascertain the required bearing stiffness, and to avoid the development of play.

The internal preload of the bearing can be obtained by means of e. g. a screwed connection. However, it is often desirable to provide a permanent connection by means of welding. A welded connection has the advantage that there is no risk of the connection becoming loose, or the preload getting lost.

In the process of manufacturing a preloaded bearing by welding, first of all the retaining ring is compressed with a specified preload onto a shoulder of the stub. This preload causes a sealing action between those components, as the result of which a closed space develops upon between the retaining ring and the stub. The air which becomes trapped in the space between the retaining ring and the stub is heated up under the influence of the welding process. As the expanding air cannot escape properly due to the sealing action addressed before, disruptions occur in the weld.

Ultimately, the air pushes away some of the still liquid parts of the weld, whereby faults develop in the completed weld.

The object of the invention is to provide an improved welding method for such bearing unit. This object is achieved by a method for welding a retaining ring on the axle stub of a vehicle bearing unit, said bearing unit comprising an outer ring, rolling elements and a two part inner ring, one part of said inner ring being constituted by an inner ring sleeve part and the other part being constituted by an inner ring stud part onto which the inner ring sleeve is fitted by means of the retaining ring which is welded onto the stud of the inner ring stud part, said retaining ring having a radial face abutting a shoulder of the inner ring stud part, comprising the steps of : -fitting the inner ring sleeve part onto the inner ring stud part, so as to bring the radial face of the retaining ring and the shoulder into abutting relationship, -providing a vent in the area of contacting faces of the retaining ring and the inner ring stud part, -compressing the radial face and shoulder onto each other,

-welding the retaining ring and the inner ring stud part at the opposite radial face of said retaining ring, while venting the welding gasses and/or trapped air through the vent.

The welding step may comprise laser welding or electron beam welding.

Through the vent, the expanding gasses may escape. There will be no internal pressure build-up, and thus no disruptions will occur and a proper weld will be obtained.

The vent or vents may be applied in several areas. According to a first possibility, a vent may be provided in the area of the abutting radial faces of the retaining ring and the inner ring stud part. According to a second possibility, a vent may be provided in at least one of the contacting axial faces of the retaining ring and the inner ring stud part.

The vents may take the form of notches in the retaining ring. Said notches may be provided in the inner axial face and/or in the radial face of the retaining ring.

The invention is also related to a vehicle bearing unit, comprising an inner ring and an outer ring each with two raceways, two series of rolling elements which are in rolling contact each with a pair of an inner and an outer raceway, the inner ring comprising an inner ring stud part carrying one of the raceways, and an inner ring sleeve part fitting onto the inner ring stud part comprising the other of the inner raceways and abutting a shoulder thereof, and a retaining ring welded on the inner part stud part and abutting the inner ring sleeve part.

According to the invention, a vent is provided on at least one of the contacting faces of the retaining ring and the inner ring sleeve part.

The invention will further be described with reference to the drawings.

Figure 1 shows a cross-section through a template for manufacturing a vehicle hub-bearing unit according to the invention.

Figure 2 shows a view, in cross-section and in perspective, of a detail of said bearing.

Figure 3 shows a sideview, partially in cross-section, of a part of the inner ring of the bearing.

Figure 4 shows a second embodiment.

Figure 5 shows a third embodiment.

Figure 6 shows a retaining ring according to the invention in perspective.

The fixture shown in figure 1 is applied for manufacturing a vehicle hub- bearing unit 1 according to the invention. This hub bearing unit comprises a bearing stud 2 and an outer ring 3.

The bearing stud 2 comprises an inner ring stud part 4 carrying an inner raceway 5, and an inner ring sleeve part 6 also carrying an inner race 7.

The outer ring comprises outer raceways 8,9.

The pairs of raceways 5,8 and 7,9 are in rolling contact each with the series of balls 10,11. The raceways 5,8 and the series of balls 10, as well as the raceways 7,9 and the series of balls 11 constitute asymmetric angular contact ball bearings 12,13, which are preloaded as will be discussed below.

The inner ring sleeve part 6 has a radial face 14, which is compressed onto a shoulder 15 of the inner ring stud part 4. In the position of contact of the radial face 14 and the shoulder 15, the asymmetric angular contact ball bearings 12,13 are preloaded to the desired magnitude.

This preload is obtained by means of a retaining ring 16, which is connected to the inner ring stud part 4 by means of a circumferential weld 17.

The welding operation is carried out while the vehicle hub-bearing unit 1 is contained in the fixture 18. This fixture 18 comprises a supporting base 19 onto which the flange 20 of the stud 2 rests. Moreover, the fixture 18 carries a cap 21, which by means of balls 22 is connected to the base 19 through support 23. The cap 21 carries a compression member 24, which by means of ball-shaped surfaces 25 is able to settle in the proper position with respect to the retaining ring 16.

The compression member 24 has a compression surface 26, which presses onto the retaining ring 16.

In the enlarged detail in perspective and in cross-section of figure 2, the retaining ring 16 is shown welded by means of weld 17 to the inner ring stud part 2.

The retaining ring 16 has a chamfered face 27, for co-operation with the compression face 26 of compression member 24.

As a result of the preload excerted on the retainer ring 16 during welding, the radial surface 14 of said retaining ring 16 is held firmly clamped onto the axial face 15 of the inner ring sleeve part 6. Thereby, a closed airspace 28 is delimited in the area delimited by the inner ring stud part 2, the inner ring sleeve part 6, the retaining

ring 16 and the weld 17. The air and gasses trapped in this space 28 can escape via the notches 29. The notches 29 are applied in the radial face 14 of the retaining ring 16.

Due to the presence of these notches 29, no pressure built up can take place in the space 28, such that a proper weld 17 is obtained.

In the cross-section shown in figure 3, one of the notches 29 is shown as well.

In the alternative embodiment of figure 4, a notch 13 is provided in the inner axial face 31 of the retaining ring 16.

According to the further alternative embodiment of figure 5, a notch 32 is provided in the radial face 15 of the inner ring sleeve part 6.

The view in perspective of figure 6 shows the retaining ring 16 according to the embodiment of figures 1-3, which has three notches 29 in its radial surface 14.