HUB-BEARING UNIT CONFIGURED FOR MOUNTING ON THE KNUCKLE OF A SUSPENSION

Abstract

A hub-bearing unit is provided with a hub, rotatable, with an axially outer flange portion configured for engagement with a rotatable element of a motor vehicle, a bearing unit provided with a fixed radially outer ring, configured for engagement with a fixed element of the motor vehicle, a first, axially outer, crown of rolling bodies, and a second, axially inner, crown of rolling bodies, interposed between the radially outer ring and the hub. The radially outer ring is held in position with respect to the knuckle by a stop ring, positioned on the axially inner side of the radially outer ring in a seat formed on the radially outer ring.

Claims

1. A hub-bearing unit comprising: a rotatable hub, provided with a flange portion axially external configured for the engagement with a rotatable element of a motor vehicle, a bearing unit having a radially outer stationary ring, configured for the engagement with a knuckle of a suspension of the motor vehicle, a first crown of rolling bodies, axially external, a second crown of rolling bodies, axially internal, interposed between the radially outer ring and the hub, wherein the radially outer ring is held in position with respect to knuckle by a stop ring, positioned on the axially inner side of the radially outer ring in a seat formed on the radially outer ring.

2. The hub-bearing unit according to claim 1, wherein a rigid connection between the radially outer ring and the knuckle is provided by a shoulder formed into the axially outer portion of the radially outer ring.

3. The hub-bearing unit according to claim 1, further comprising an encoder, located on an axially inner edge of the hub, which faces a speed sensor, wherein the stop ring is in an axially external position with respect to the encoder.

4. The hub-bearing unit according to claim 1, wherein the hub also assumes the function of the radially inner ring of the bearing unit and the bell of a constant velocity joint.

5. The hub-bearing unit according to claim 1, further comprising a bushing for centering the rotatable element of the motor vehicle.

6. The hub-bearing unit according to claim 5, wherein the bushing is rigidly connected to the flange of the hub.

7. The hub-bearing unit according to claim 5, wherein the bushing is made in one piece with the hub.

8. The hub-bearing unit according to claim 1, further comprising a protection cap for grease containment inside the constant velocity joint.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0021] The invention will now be described with reference to the attached drawing, showing some non-limiting exemplary embodiments of the invention, in which:

[0022] FIG. 1 is an axially symmetrical section through the hub-bearing unit according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0023] With reference now to FIG. 1, a hub-bearing unit according to a first embodiment of the invention is indicated as a whole by 10.

[0024] The unit 10 also provides a hub 20 and a bearing unit 30. Throughout the present description and claims, any terms and expressions indicating positions and orientations such as “radial” and “axial” are to be interpreted as relating to the central axis of rotation X of the bearing unit 30. However, expressions such as “axially outer” and “axially inner” refer to the assembled condition, and in the present case preferably refer to a wheel side and to a side opposite the wheel side, respectively.

[0025] The bearing unit 30 provides a fixed radially outer ring 31 and two rings of rolling bodies 32, 33, in this example balls, interposed between the radially outer ring 31 and the hub 20 which acts as the radially inner ring. To simplify the graphic representation, the references 32 and 33 are used to indicate both individual balls and rings of balls; in particular, 32 indicates the axially outer crown of balls or individual ball, and 33 indicates the axially inner crown of balls or individual ball. Also for the sake of simplicity, the term “ball” is frequently used by way of example in the present description and in the appended drawings, rather than the more generic term “rolling bodies” (and the same reference numerals are also used). However, it should be understood that any other rolling bodies (such as rollers, tapered rollers, needle rollers, etc.) may be used in place of the balls.

[0026] FIG. 1 shows the case of a symmetrical bearing, that is to say a bearing having the same pitch diameter for both crowns of rolling bodies. The content of the rest of the present description is also applicable to the case of an asymmetrical bearing, the only substantial difference between the two bearing types being that, whereas the diameters of the circumferences of the centres of the rolling bodies of the corresponding rings 32, 33 have the same value in a symmetrical bearing, the aforesaid diameters differ from each other in an asymmetrical bearing. The radially outer ring 31, preferably in the shape of an axially extended tube, defines within itself the races 34, 35 for the corresponding rolling bodies of the crowns 32, 33.

[0027] The rolling bodies of the crowns 32, 33 rotate not only on the radially outer ring 31 but also on a central tubular portion 21 of hub 20, which defines a race 36 for the rolling bodies of the axially outer crown 32 and an axially inner race 37 for the rolling bodies of the crown 33. The hub 20 therefore acts as a single inner ring, replacing the two inner rings which, as is well known, are commonly used in standard solutions for flanged hub-bearing units. The phonic wheel 38 and the sealing element 39 are stably fixed on the axially inner side of the hub 20. A speed sensor 80, for example the sensor of the anti-lock braking system (ABS) of the motor vehicle wheel, faces the phonic wheel 38.

[0028] The hub 20 also defines a shoulder 22, on the axially inner side, and an axially outer flange portion 23. The flange portion has a plurality of axial fixing holes 24 and seats for the same number of fixing means (such as captive bolts, not shown in the drawing), which connect an element of the motor vehicle wheel, for example the brake disk (also of a known type, not shown in the drawing), to the hub 20.

[0029] Advantageously, a bushing 50 for centring the motor vehicle wheel may be made from sheet metal, steel for example, and coupled to the flange portion 23 of the hub, preferably by a simple press-fitting operation. Alternatively, this bushing 50 may be made in one piece with the hub 20.

[0030] Transmission of motion from a half-axle of the transmission assembly of a motor vehicle (not shown) is provided by a constant velocity joint 60. In particular, the outer bell of the joint 60 is integrated into the hub 20, which defines the race 62 of the joint in its axially inner terminal part 61. The grease is contained inside the constant velocity joint by isolating the joint from the outside by means of a protection cap 63.

[0031] The radially outer ring 31 has a radially outer cylindrical surface 31a adapted to be coupled to a cylindrical seat formed in a fixed element of the vehicle, for example a knuckle of a suspension, shown schematically in the drawing with the reference 40. The cylindrical surface 31a extends over a large part of the axial dimension of the radially outer ring 31, and has an axial dimension of the same order of magnitude as the cylindrical seat of the knuckle.

[0032] The radially outer ring 31 is coupled, by a radial interference fit for example, to the knuckle 40, and is held in place relative to the knuckle by means of a stop ring 70 of the Seeger type, positioned on the axially inner side of the outer ring 31 and having a seat 31c formed on the same outer ring.

[0033] As is known, a Seeger ring is a stop ring, normally made of elastic steel, the circumference of which is incomplete, with holes present at the two ends for fitting the ring, by means of pliers for example.

[0034] A shoulder 31b, formed in the axially outer portion of the outer ring 31, may also be provided in the coupling between the radially outer ring 31 and the knuckle 40.

[0035] In the solutions according to the present invention, the stop ring 70 is mounted on the axially inner side, which is subject to less stress, while still being in an axially outer position with respect to the phonic wheel 38 fixed to the rotatable ring of the bearing, that is to say to the hub 20. This means that the speed sensor 80 of the ABS, which must be placed next to the phonic wheel, may easily be accommodated in the correct position.

[0036] The advantage of this solution is that a section with a desired degree of robustness can be designed in the axially outer area of the outer ring 31 (either in the presence or in the absence of the shoulder 31b), in order to withstand the predominant stresses in this area in a reliable manner.

[0037] Thus the present solutions require no orbital forming procedure, and consequently there is no need to carry out plastic deformation procedures.

[0038] This advantage automatically entails other benefits: since there is no need for cold plastic machining, the choice of material for the bearing is wider, depending on other types of requirement and convenience. Similarly, there is no need to carry out any forming, given that not all materials are suitable for certain types of deformation.

[0039] Furthermore, the plastic deformation process required the use of an induction tempering system for the races. In this case, a total tempering process may be used as an alternative, and the choice between the two hardening processes may be made on the basis of other requirements such as the process or the cost.

[0040] Finally, there is no need to handle the knuckle together with the bearing to form a pre-assembled unit; instead, the hub-bearing unit may be sent directly to the end user, with considerable benefits in terms of logistics and costs. It should be noted that the assembly of the hub-bearing unit requires no particular attention and entails no particular difficulties for the end user.

[0041] It is to be understood that the invention is not limited to the embodiments described and illustrated herein, which are to be considered as examples of the unit; it will be evident to persons skilled in the art that various changes may be made to the functions and configuration of the elements described as exemplary embodiments, without departure from the scope of the invention as defined in the appended claims and in their equivalents.