The invention relates to vehicle wheel hubs, namely to those case-like structures with bearings which support the wheel and the brake disc and which are designed to be constrained in a fixed or articulated manner to the rear axle unit or the front axle unit of a motor vehicle.
In particular, the invention relates to the wheel hubs of the type shown in
In the wheel hub in question the crown part of the rolling means 2 travels along an annular track 4 formed directly on the outer side surface of the spindle 1, while the other crown part of rolling means 102 travels along an annular track 104 formed on a ring 5 which is mounted on an externally tapered portion 201 of the spindle 1 and is firmly fixed onto the latter by means of abutment against an inner shoulder 6 and against an outer edge 201′ formed, during a step following said mounting operation, by means of rolling of the section, projecting from the ring 5, of the said support portion 201 of the spindle.
The space inside which the crown parts of the rolling means 2, 102 operate is filled with lubricant and is closed by known sealing means 7, 107.
Practical experience has shown that the force exerted by the annular rolled edge 201′ on the inner ring 5 of the bearing is more than sufficient to lock axially this ring on the associated support part, but instead is not able to prevent any accidental relative rotation of the ring 5 and spindle 1, in particular when considerable friction is present between this ring and the associated crown part of rolling means 102. This condition may cause vibrations and noise, may reduce the average working life of the bearing and, if neglected, may result in overheating and breakage of the tapered support portion 201, 201′ of the spindle 1 which may freely disengage from the casing 3, with the consequences which may be imagined.
In order to overcome this serious drawback, the known art teaches that it is possible to mount the ring 5 on the spindle 1 using keying means arranged in between and consisting for example of splined male and female profiles which are formed longitudinally on the outer surface of the spindle and on the inner surface of the ring 5 and which may thus be engaged without any possibility of relative rotation and the axial movements of which are also prevented by means of rolling of the edge 201′. This solution is, for example, illustrated in the US patent application 2002/0025093 published on 28 Feb. 2002 entitled “Bearing device for drive wheel”.
This same solution, however, has the drawback of a high production cost in that the formation of the said keying grooves requires specific machining techniques with setting of the workpieces on machine tools different from turning machine tools.
Still with the aim of overcoming the serious drawback mentioned above, also known is the solution (described in the U.S. Pat. No. 7,241,054) which can be produced on an industrial scale at a very low cost, during the same operation of turning the workpieces and which envisages the formation, on the side surface for engagement between ring 5 and spindle 1, of sections with a radially multiple-lobe form, for example a three-lobe form.
Although, this solution, on the on hand, offers the advantage compared to the previous solution of being able to be produced with very low costs, on the other hand it results in difficulties during engagement between the parts 5 and 1, owing to the need to correctly align these same parts relative to each other, both in the axial direction and in the angular direction, even before they are axially engaged together.
The object of the invention is to solve this technical problem of engagement, in particular to simplify this engagement operation and simplify the formation of the keying means, with a method as described in claim 1 and in the subsequent dependent claims, based on the following proposed solution: the machining operation for the three-lobe engaged arrangement is performed so as to involve all or only partly the shoulder 6 and the corresponding inner end of the ring 5, so that the latter may be mounted on the portion 201 of the spindle 1 as though these two parts were two normal parts with a round cross-section and therefore without any need for relative angular alignment and, only after these two parts have been engaged together axially, is a relative rotation of the said parts performed in order to engage correctly the three-lobe profile of the ring 5 with the corresponding three-lobe profile of the shoulder 6 of the spindle and vice versa and, after this step involving correct angular alignment, the said axial locking edge 201′ will be formed by means of rolling.
Further characteristic features of the invention and the advantages arising therefrom will emerge more clearly from the following description of a preferred embodiment thereof illustrated purely by way of a non-limiting example in the figures of the two accompanying sheets of drawings in which, in addition to the already considered
In the wheel hub shown in
According to the invention, when the spindle 1 is machined on the turning machine, the angle zone of its shoulder 6 is provided with a multiple-lobe machined zone, for example having a three-lobe profile as shown in
Likewise, during machining of the ring 5 on the turning machine, its edge and/or its front face intended to co-operate with the said shoulder 6 of the spindle 1 is provided with three-lobe recesses 100, as can be seen from
The result of the above is that the inner side surface of the ring 5 remains over its length, except for the small end part which may be occupied by the said three-lobe profile 100, perfectly cylindrical and with a round cross-section, similar to the entire length of the outer side surface of the portion 201 of the spindle, so that mounting of the ring 5 on this part 201 of the spindle is an extremely easy operation since the two parts must not be necessarily aligned with each other angularly before axial engagement. The recessed three-lobe profile 100 provided on the inner edge of the ring 5 forms, moreover, an effective guide means which facilitates correct axial engagement of the parts, even if these are not perfectly aligned axially.
Only subsequently, once the ring 5 has been mounted on the portion 201 of the spindle, will a small relative rotation of the two parts be performed and the latter pushed lightly against each other so as to cause the recessed three-lobe profile 100 of the ring 5 to engage with the raised three-lobe profile 10 of the shoulder 6 of the spindle, and this engaged condition may be easily detected with sensors since, when it occurs, the ring 5 touches the shoulder 6 and engages with the portion 201 of the spindle over the appropriate length, without performing any axial displacement on this portion 201.
When engagement of the aforementioned parts 201 and 5 has been performed, before subjecting them to the rolling procedure for formation of the locking edge 201′, the ring 5 may if necessary be locked in the correct angular position on the portion 201 of the spindle, with the prior or subsequent application of a few drops of adhesive, in any manner suitable for the purpose.
When the multiple-lobe parts 10 and 100 are engaged together, the same parts will form a small engaging joint partly of the radial type and partly of the frontal type or exclusively of the frontal type, this preventing relative rotation of the ring 5 and spindle 1 and the associated serious problems mentioned in the introductory part of the present description.
It is evident how the method described, in addition to simplifying the operation of keying the ring 5 onto the spindle 1, also simplifies the operation of forming the three-lobe profiles 10 and 100, since the same profiles are situated on a surface covering a small area, decidedly much smaller than that envisaged by the prior art according to the U.S. Pat. No. 7,241,054 mentioned in the introduction.
If the wheel hub is of the type shown in
Number | Date | Country | Kind |
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BO2008A000171 | Mar 2008 | IT | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP09/53097 | 3/16/2009 | WO | 00 | 11/12/2010 |