Flanged wheel hub unit and assembly method

Abstract

A wheel hub unit having a rotatable hub provided with an axially outer flange and a bearing unit. The bearing unit providing a radially outer ring, a radially inner ring and a plurality of rolling bodies positioned respectively between the radially outer ring and the hub and between the radially outer ring and the radially inner ring. The radially inner ring has a finished axial length which ensures a predetermined value of an axial preload of the bearing unit and a finished axial length is defined by the following formula: X=(X+X)X1

Claims

1. A method of assembling a wheel hub unit for motor vehicles, comprising: providing a rotatable hub, and a bearing unit having: a radially outer ring, a radially inner ring, and a plurality of rolling bodies respectively positioned between the radially outer ring and the hub and between the radially outer ring and the radially inner ring, the method being suitable for ensuring a predetermined value of an axial preload () of the bearing unit and comprising the following steps: assembling the radially inner ring in a semifinished configuration provided with an available oversize (X), a predetermined amount of which is to be removed from an axially outer annular surface of the radially inner ring, measuring an axial clearance of the bearing unit present between a shoulder edge of the radially inner ring and an axially inner end of the rolling bodies, disassembling the radially inner ring from the bearing unit, calculating a portion of the available oversize to be removed from the axially outer annular surface of the radially inner ring, the value of the oversize to be removed being equal to a sum of the value of the axial clearance and the predetermined value of the axial preload (). removing from the axially outer annular surface of the radially inner ring the oversize to be removed, assembling the radially inner ring in a finished configuration on the bearing unit, wherein the radially inner ring has a finished axial length which ensures the predetermined value of the axial preload () of the bearing unit.

2. The method according to claim 1, wherein the finished axial length of the radially inner ring is calculated as follows:
X=(X+X)- X1 wherein: X: nominal axial length of the radially inner ring, X: oversize available on an axially outer annular surface of the radially inner ring, X1: oversize removed from the axially outer annular surface of the radially inner ring.

3. The method according to claim 1, wherein the radially inner ring is configured to be realized from a semifinished element having an axial length (X+X), which is a sum of the nominal axial length (X) and the available oversize (X) on the axially outer annular surface of the radially inner ring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described with reference to the attached drawings which illustrate a non-limiting example of embodiment thereof, in which:

(2) FIG. 1 schematically shows a wheel hub unit, in which the assembly method and the associated axial preload are realized according to the prior art;

(3) FIG. 2 shows a partial axial-symmetrical section through the wheel hub unit provided with a rolling bearing according to a mode of implementation of the present invention;

(4) FIG. 3 shows in schematic form the radially inner ring of the unit shown in FIG. 2;

(5) FIG. 4 shows a step during assembly of the unit according to FIGS. 2; and

(6) FIG. 5 shows in schematic form a further step during assembly of the unit according to FIG. 2.

DETAILED DESCRIPTION

(7) With reference to FIG. 2, 10 denotes in its entirety a wheel hub unit according to a preferred embodiment of the invention. As mentioned in the introduction, the invention is applicable not only to the configuration described below, but generally to any wheel hub unit for motor vehicles.

(8) The unit 10 comprises a hub 20 which is preferably, but not necessarily, rotatable and a bearing unit 30. The hub 20 is configured to assume also the function of an inner rolling ring of the bearing. In the whole of the present description and in the claims, the terms and expressions indicating positions and orientations such as radial and axial are understood as referring to the central axis of rotation A of the bearing unit 30. Expressions such as axially outer and axially inner refer instead to the assembled condition and, in the specific case, preferably refer to a wheel side and, respectively, to a side opposite side to the wheel side.

(9) The bearing unit 30 comprises a radially outer ring 31 which is stationary and provided with respective radially outer raceways, at least one radially inner ring 20, 34 which is rotatable and provided with respective radially inner raceways, and two rows of rolling bodies 32, 33, in this example balls. The axially outer row of rolling bodies 32 is arranged between the radially outer ring 31 and the hub 20 with the function of a radially inner ring, while the axially inner row of rolling bodies 33 is arranged between the radially outer ring 31 and the radially inner ring 34. For the sake of easier illustration, the reference numbers 32, 33 will be used to identify both the single balls and the row of balls and in particular 32 will indicate the axially outer row of balls or single ball, while 33 will indicate the axially inner row of balls or single ball. Again, for the sake of simplicity, the term ball may be used by way of example in the present description and in the attached drawings instead of the more generic term rolling body (and likewise the same reference numbers will also be used). It will be understood always that, instead of balls, any other rolling body (for example, rollers, tapered rollers, needle rollers, etc.) may be used.

(10) The bearing unit 30 is sealed by suitably designed sealing elements 35, 36 which are sliding sealing elements, as per the prior art. The rolling bodies of the rows 32, 33 are kept in position by corresponding cages 39, 40.

(11) The hub 20 defines at its axially inner end a rolled edge 22 which is configured to preload axially the inner ring 34. The hub 20 also has an axially outer flange portion 23. The flange portion has a plurality of axial fixing holes 24. These holes are the seats for corresponding fixing means (for example stud bolts, not shown in the figures) which connect in a known manner a part of the motor vehicle wheel, for example the brake disc (also known per se and not shown in the figures), to the hub 20.

(12) With reference to FIG. 3, the wheel hub unit according to the invention is distinguished in that the radially inner ring 34, in a semifinished form, has a nominal axial length X increased by an amount equal to X which represents the oversize thickness, a predetermined amount of which will then be removed. The value of X, purely by way of example, may range between 0.05 mm and 0.1 mm. The oversize thickness actually removed X1 may be less than or greater than the value of X, depending on the specific application, the preload value required and the tolerances of the axial lengths of the components. Consequently, the finished axial length X of the radially inner ring may be greater than or less than the nominal axial length X.

(13) With reference to FIG. 4 the assembly method according to the present invention envisages preassembly of the inner ring with a length X+X and the measurement of the axial clearance y between the shoulder edge 34 of the radially inner ring 34 in the semifinished configuration, and the ball 33, more precisely the axially inner end of the ball 33.

(14) The radially inner ring will then be disassembled. Based on the measurement of the axial clearance y the amount of the oversize X1 to be removed from the axially outer annular surface 34 of the radially inner ring 34 in order to obtain the correct axial preload is calculated. Clearly it is necessary for:
X1>y

(15) and the difference between the two parameters forms the value of the preload required by the application. Once it has been adjusted to its finished value, for example, by means of precision-machining, the radially inner ring may be definitively assembled on the wheel hub unit.

(16) With reference to FIG. 5, the finished axial length of the radially inner ring 34 will therefore be X, whereby the following relation applies:
X=(X+X)X1

(17) where, it is stated again:

(18) X: the nominal axial length of the radially inner ring 34

(19) X: oversize available

(20) X1: oversize removed

(21) X: the finished axial length of the radially inner ring 34

(22) To summarize, the solution according to the invention is that of adjusting the annular surface 34 of the radially inner ring 34 so that it assumes a finished axial length X such as to ensure the correct preload value, according to the following assembly method:

(23) assembling the radially inner ring 34 provided with an available oversize X, a predetermined amount of which is to be removed, where the value of the oversize removed X1 may be less than or greater than the value of the available oversize X,

(24) measuring the axial clearance y of the bearing, between the shoulder edge 34 of the radially inner ring 34 and the axially inner end of the ball 33,

(25) disassembling the radially inner ring from the bearing 30,

(26) calculating the oversize X1 to be removed from the surface 34 of the radially inner ring 34, where
X1=y+

(27) adjusting the axially outer annular surface 34 of the radially inner ring 34 until a value of the removed oversize equal to X1 is obtained,

(28) final assembly of the radially inner ring 34 on the bearing, with a finished axial length X which ensures the correct axial preload value.

(29) The many advantages which may be obtained by the present invention are clear. In particular, as a result of the invention it is possible to avoid the presence and the management of huge warehouse stocks of the various categories of radially inner rings or, alternatively, categories of balls. Moreover, since according to this method, it is not required to use sample components and therefore the radially inner ring is mounted together with the components which will actually form the bearing, it is possible to reduce the spread of the measurements and increase the process capability. The method does not require investment in new production lines since it is possible to use the existing ones. Finally, since the division of the radially inner ring (or balls) into categories may be avoided, the space requirement of the production line will be significantly reduced.

(30) In addition to the embodiments of the invention, as described above, it is to be understood that numerous further variants are possible. It must also be understood that said embodiments are only examples and do not limit the subject of the invention, nor its applications, nor its possible configurations. On the contrary, although the description provided above enables the person skilled in the art to implement the present invention at least in one of its examples of configuration, it must be understood that numerous variations of the components described are feasible, without thereby departing from the scope of the invention, as defined in the accompanying claims, interpreted literally and/or in accordance with their legal equivalents.