Hub bearing unit for wheel of motor vehicle

Abstract

A hub bearing unit having an axis of rotation and having:-a stationary radially outer ring,-a flanged hub radially inward of the radially outer ring and rotatable both relative to the axis and relative to the radially outer ring; the invention relates to a toothed hub assembly comprising a flanged hub having a toothed profile and an axially inner tubular portion, a radially inner ring mounted on the flanged hub in an axially abutting manner, a toothed sleeve mounted axially proximate to the radially inner ring and angularly coupled to the toothed profile of the flanged hub by an inner slot, wherein the toothed sleeve is provided with axially and radially inner steps having a radially inner cylindrical surface, and the tubular portion of the flanged hub has a radially outer cylindrical surface, the two cylindrical surfaces being precisely coupled to each other such that it is ensured that the toothed sleeve is centered relative to the flanged hub.

Description

Technical Field

[0001] The present invention relates to a hub-bearing unit for a wheel of a motor vehicle. The unit comprises a bearing unit which is removably coupled to a constant velocity joint and is therefore suitable for both a drive wheel and a driven wheel. Background Art

[0002] In the prior art, a wheel hub bearing unit comprises a flanged rotating hub mechanically connected to a rotating element of a motor vehicle (e.g., a wheel or a disc of a brake element), and the bearing unit comprises an outer ring, a pair of inner rings (one of which may be the flanged hub itself) and a plurality of rolling elements (e.g., balls). All of these components (e.g., the flanged hub and the inner ring of the bearing unit) have axial symmetry about the axis of rotation of the rotating element.

[0003] The flanged wheel hub receives the driving torque from the bell housing of the constant velocity joint via a splined coupling. In particular, the bell housing of the constant velocity joint is provided with axially outer toothing, while a toothed sleeve with axially outer toothing is fastened to the wheel hub. The toothed sleeve and the wheel hub are coupled to each other by means of an inner groove of the toothed sleeve, which engages with the toothed profile of the wheel hub.

[0004] A ring gear with axial internal teeth transmits the motion from the constant velocity joint to the wheel hub, and the ring gear is provided with a system for disconnecting from the toothed sleeve of the wheel hub. Thus, when the ring gear is engaged with the toothed sleeve of the wheel hub, the motion is transmitted from the drive shaft to the wheel of the motor vehicle, which then acts as a driving wheel. Conversely, when the ring gear is disengaged from the toothed sleeve of the wheel hub, the motion transmission from the drive shaft to the wheel is interrupted, and the wheel acts as a driven wheel.

[0005] In this configuration, bearings are required between the hub and the CV joint to allow the hub to rotate independently of the CV joint. These bearings are typically radial ball bearing types.

[0006] By known processes (such as orbital roll forming), the axial inner appendage of the flanged hub is deformed to axially preload and clamp both the toothed sleeve and the radial inner ring (mounted on the flanged hub) relative to the flanged hub itself.

[0007] The coupling and centring between the toothed sleeve and the hub is obtained by engaging the internal groove of the toothed sleeve with the external toothed profile of the flanged hub. Since a certain degree of play is required between the internal groove of the toothed sleeve and the toothed profile of the hub, effective centring between the two component parts cannot be ensured. The play depends on the manufacturing accuracy (tolerance grade), is defined by the specifications of the groove standard (such as ANSI B92.1, DIN 5480 or others), and is equal to the radial space between the engaging profiles of the two grooves. During the assembly operation, before and during the track roll forming operation, this play can lead to radial movement of the toothed sleeve relative to the hub. The subsequent eccentricity of the toothed sleeve relative to the hub leads to subsequent problems of engagement between the toothed sleeve and the ring gear connected to the constant velocity joint, as well as vibrations and / or noise during the period when the separation system is inserted. Summary of the invention

[0008] The invention aims at providing a wheel hub bearing unit coupled to a system for decoupling from a transmission shaft, wherein the wheel hub comprises a cylindrical surface coupled to a corresponding discontinuous or continuous cylindrical surface of a toothed sleeve.

[0009] The present invention therefore provides a wheel hub bearing unit having the features set out in the independent claim appended to this description.

[0010] Further preferred and / or particularly advantageous embodiments of the invention are described according to the features stated in the attached dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The invention will now be described with reference to the accompanying drawings, which show non-limiting embodiments, in which:

[0012] - Figure 1 shows a cross section of a hub bearing unit according to a preferred embodiment of the present invention,

[0013] - Figure 2 Shows Figure 1 An enlarged view of a detail of the hub bearing unit in which the hub is in the configuration before the plastic deformation process,

[0014] - Figure 3an enlarged view showing a detail of a hub bearing unit in a second embodiment of the invention and in which the hub is in a configuration prior to the plastic deformation process, and

[0015] - Figure 4 An enlarged view showing further details of a wheel hub bearing unit according to the preceding solution. DETAILED DESCRIPTION

[0016] refer to Figure 1 A hub-bearing unit according to a preferred embodiment of the present invention is generally denoted by reference numeral 10 .

[0017] When in use, the hub bearing unit 10 is interposed between the wheel and the frame of the vehicle, both of which are known and not shown, and the hub bearing unit 10 can be selectively connected to a known and not shown constant velocity joint ( / constant velocity joint) via a transmission device also known and not shown, for transmitting or not transmitting the driving torque to the corresponding wheel (not shown).

[0018] The hub bearing unit comprises a rotating flanged hub 20 and a bearing unit 30 having a central axis of rotation X and comprising:

[0019] - a stationary radial outer ring 31, and

[0020] - a radial inner ring 20 defined by the flanged hub 20 and a further radial inner ring 34 mounted on and rigidly connected to the flanged hub 20, the two radial inner rings 20, 34 rotating relative to the radial outer ring 31 due to the interposition of two rows of rolling elements 32, 33 (in this case balls).

[0021] Throughout the specification and claims, terms and expressions indicating positions and orientations, such as "radial" and "axial", should be understood with reference to the central rotation axis X of the bearing unit 30. On the other hand, expressions such as "axially outer" and "axially inner" are for the installation state of the hub bearing unit, and in this case, preferably refer to the wheel side and the side opposite to the wheel side, respectively.

[0022] The flanged hub 20 has a central through hole 21 extending along the axis X so as to engage with a constant velocity joint, and includes a flange 25 on the axially outer side of the flanged hub 20 for fastening the hub bearing unit 10 of the wheel of the vehicle, and includes an end edge 24 rolled by orbital roll forming on the axially inner side of the flanged hub 20, which is designed to axially preload both the inner ring 34 and the toothed sleeve 55 against the radial outer shoulder 22 of the flanged hub 20, the toothed sleeve 55 mounted against the inner ring 34 is connected to the toothed profile 23 of the flanged hub 20 through an inner groove 56, and is part of a known transmission device that is connected or disconnected ( / disconnected) by an external toothed profile 57.

[0023] A bearing is required between the wheel hub and the constant velocity joint so that the flanged wheel hub 20 can rotate independently of the constant velocity joint when the flanged wheel hub 20 is disengaged from the constant velocity joint. In the embodiment of the present invention, the flanged wheel hub 20 has a first radial inner shoulder 26 and a second radial inner shoulder 27 formed inside the central through hole 21, and at least two radial ball bearings 60, 61 are installed near the first radial inner shoulder 26 and the second radial inner shoulder 27 (in the embodiment of the present invention). Figure 1 Two radial ball bearings 60, 61 are mounted in radially inner positions relative to the flanged hub 20. In particular, the first radial ball bearing 60 is mounted in an axially outer position against the first shoulder 26, and the second radial ball bearing 61 is mounted in an axially inner position against the second shoulder 27. It is noted that there may also be a second radial ball bearing in an axially inner position.

[0024] Figure 2 The rail roll forming operation is shown in the configuration prior to the rail roll forming operation. Figure 1 The axial inner part of the hub bearing unit (particularly the axial inner tubular part 50 of the flanged hub 20 ) and the toothed sleeve 55 .

[0025] The toothed sleeve 55 has an internal groove extending therethrough in the axial direction, and the toothed profile 23 of the flanged hub 20 has an axial length that is smaller than the axial length of the internal groove 56 .

[0026] According to the invention, the toothed sleeve 55 has an axially and radially inner step 58 with a radially inner discontinuous cylindrical surface 59 formed by the surface of the crests of the inner groove 56. Correspondingly, the tubular portion 50 of the flanged hub 20 has a radially outer cylindrical surface 29. This cylindrical surface 29 is axially inside the toothed profile 23 and axially outside the end edge 24. The two cylindrical surfaces - the cylindrical surface 59 of the step 58 of the toothed sleeve 55 and the cylindrical surface 29 of the tubular portion 50 of the flanged hub 20 - are precisely coupled to each other, so that optimal centring of the toothed sleeve 55 relative to the flanged hub 20 is ensured.

[0027] Improved centering between the two components brings many advantages:

[0028] - improving the coaxiality between the flanged hub 20 and the toothed sleeve 55,

[0029] - Improve the coaxiality between the toothed sleeve 55 and the radial inner ball bearings 60, 61,

[0030] - Improvement of the mechanical strength of the toothed sleeve 55 with respect to the stresses caused by the track roll-forming operation. In particular, due to the presence of the step 58, stresses are reduced and radial expansion is reduced by virtue of the greater radial thickness of the toothed sleeve 55 (relative to known solutions),

[0031] - Relief of engagement problems of the disconnection system by means of improved centering and reduced radial expansion of the toothed sleeve 55,

[0032] - Reduce possible vibration and noise problems when the separation system is inserted.

[0033] Advantageously, the coupling between the two cylindrical surfaces 29 , 59 is uncertain: the machining tolerances of the two surfaces may therefore define a coupling with a “slight” play or a coupling with a “slight” interference.

[0034] Preferably, the diameter D of the centering cylindrical surface 29 of the flanged hub 20 is 29The following restrictions should be met:

[0035] - diameter D of the cylindrical surface 29 29 It should be smaller than the diameter D of the bottom cylindrical surface 23' of the toothed profile 23 of the flanged hub 20. 23' , to ensure the feasibility of producing the tooth profile. Even more preferably, the diameter D 29 Should be larger than the diameter D 23' At least 0.01mm smaller. In other words:

[0036] D 29 ≤D 23' -0.01mm

[0037] - diameter D of the cylindrical surface 29 29 It should be larger than the diameter D of the radially outer cylindrical surface 24' of the end edge 24 of the flanged hub 20. 24' Even more preferably, the diameter D of the cylindrical surface 29 is 29 The diameter D of the surface 24' 24' The difference should be between 0.1 mm and 1 mm.

[0038] When establishing the diameter D of the cylindrical surface 29 29 When setting the maximum possible value of , the thickness s of the end edge 24 to be rolled should be considered. This thickness is selected based on the structural requirements of the application and the orbital roll-forming operating parameters selected for the component.

[0039] The axial length L of the centering cylindrical surface 59 of the toothed sleeve 55 should be at least 1 mm. However, consideration must be given to the fact that the maximum axial length L is bounded by the axial length of the inner groove 56 of the toothed sleeve 55, the selection of which depends on the torque transmission requirements and is defined according to the specifications of the groove standard.

[0040] Figure 3 A similar axial inner portion of a hub bearing unit 10 ′ according to an alternative embodiment of the invention is shown.

[0041] The only difference between the two constructions is the toothed sleeve 55' and for this reason this alternative embodiment of the invention consists of Figure 3 A single detail is shown in Figure 1, and all other features are similar to Figure 1 and Figure 2 The embodiment shown in is the same.

[0042] In this embodiment, unlike the case shown above, the toothed sleeve 55' has an inner groove 56' which does not pass through the step 58' in the axial direction and is limited by the step 58' in the axial direction. Therefore, the step 58' has a centering cylindrical surface 59' which is continuous instead of being discontinuous as in the above-described configuration. There is no change with respect to the centering cylindrical surface 29 of the flanged hub 20 or with respect to the above-described design requirements.

[0043] This embodiment of the invention has the additional advantage over those already listed above, namely that the axial inner surface 65' of the toothed sleeve 55 (which supports the rolled end edge ( / rolled end edge) 24 of the flanged hub 20) does not exhibit any discontinuities due to the empty spaces between the teeth (however, discontinuities are present in the corresponding surface 65 of the toothed sleeve 55 of the first embodiment of the invention). As a result, the rolled material of the end edge 24 is pressed against a continuous surface (approximately over the entire 360° circumference) without empty spaces. This avoids material discontinuities that could lead to a concentration of stresses and potential crack initiation points on the rolled material ( / rolled material).

[0044] refer to Figure 4 ,for Figure 1 and Figure 2 The implementation method and Figure 3 In both alternative embodiments, advantageously, the axial stop for the second radial ball bearing 61 is formed by a spacer 70 located radially inside the flanged hub 20 and axially outside the radial ball bearing 61. The spacer 70 is in turn blocked axially against the second axial shoulder 27 of the flanged hub 20.

[0045] More specifically ( / more particularly), the two radial bearings 60, 61 and the spacer 70 are pressed against the shoulders 26, 27 by rings (known and not shown), thereby applying axial compression force to the flanged hub 20 through the outer rings of the bearings 60, 61 and the spacer 70, and the axial compression force responds to the stress transmitted by the wheel and generates a reaction force on the shoulders 26, 27 (and in particular on the axially inner ( / inner) second shoulder 27), because the shoulders 26, 27 (and in particular the axially inner second shoulder 27) are located in the highest stress part of the flanged hub 20 (i.e., the tubular part 50).

[0046] The presence of the spacer 70 makes it possible to improve the geometry of the flanged hub 20 in terms of tension. In fact, in order to be able to perform a grinding operation on the radially inner seat 28 of the flanged hub 20, said seat housing the second radial ball bearing 61 and the spacer 70, it is necessary to define a relief groove 80 between the seat 28 and the second axial shoulder 27 of the flanged hub 20. The relief groove 80 is therefore located axially outside the seat 28 and radially inside the entire flanged hub 20. The presence of the spacer 70 enables the relief groove 80 to be sufficiently far away from the tubular portion 50 of the flanged hub 20.

[0047] Therefore, the spacer 70 including an axial shoulder for the axially inner radial ball bearing 61 is primarily intended to be able to provide a radially inner ( / radially inside) relief groove 80 that is different in shape and position from the relief groove that can be provided in the absence of the spacer 70.

[0048] Thus, the inclusion of the spacer 70 enables a number of advantages to be achieved:

[0049] the radially inner relief groove 80 is arranged at a more axially outer position and therefore further away from the tubular portion 50 of the flanged hub 20 which is the most stressed area of ​​the hub,

[0050] - the geometry of the relief groove 80 is characterized by a large radius and a large overall length, thereby reducing the notch effect,

[0051] - If the application requires, it is also possible to include an axially inner second radial ball bearing next to the first ball bearing, without modifying the flanged hub, but only reducing the axial size of the spacer 70. A second radial ball bearing may be useful in cases where one ball bearing is not sufficient to withstand the stresses from the constant velocity joint.

[0052] In summary, the invention solves the technical problem by achieving optimal centering of the toothed sleeve relative to the flanged hub. This translates into a more robust design of the hub bearing unit and improved conditions of use.

[0053] In particular, in terms of design, the advantages are:

[0054] - Improved coaxiality between flanged hub and toothed sleeve,

[0055] - Improved coaxiality between the toothed sleeve and the radial internal ball bearing,

[0056] - Improved mechanical strength of the toothed sleeve with respect to stresses caused by the rail roll forming operation.

[0057] In addition, for Figure 3 The embodiments of the present invention eliminate stress concentrations and crack initiation points on the rolled material of the flanged hub during and after the rail roll forming operation.

[0058] Finally, from the end-user perspective, this solution makes it possible to:

[0059] - Improved process for engaging the release system by means of improved centering and reduced radial expansion of the toothed sleeve,

[0060] - Reduction of possible vibration and noise problems when the separation system is plugged in, which is a particularly important aspect in the case of electric vehicle applications.

[0061] In addition to the embodiments of the present invention as described above, it should be understood that there are many other variations. It should also be understood that these embodiments are exemplary only and do not limit the scope of the present invention, its application or its possible configuration. On the contrary, although the above description enables those skilled in the art to implement the present invention according to at least one exemplary embodiment of the present invention, it should be understood that many variations of the described components are possible without departing from the scope of the present invention as defined in the appended claims, literally and / or interpreted according to its legal equivalents.

Claims

1. A hub bearing unit (10, 10') having a rotation axis (X) and comprising: - radial outer ring (31), which is fixed, a flanged hub (20) situated radially inside the radially outer ring (31) and rotatable both relative to the axis (X) and relative to the radially outer ring (31); the flanged hub (20) having a toothed profile (23) and an axially inner tubular portion (50), - a radial inner ring (34) mounted in axial abutment on the flanged hub (20), - a toothed sleeve (55, 55') mounted axially close to the radial inner ring (34) and angularly coupled to the toothed profile (23) of the flanged hub (20) via internal grooves (56, 56'); The unit (10, 10') is characterized in that the toothed sleeve (55, 55') comprises an axially and radially inner step (58, 58'), which has a radially inner cylindrical surface (59, 59'), and the tubular part (50) of the flanged hub (20) has a radially outer cylindrical surface (29), the two cylindrical surfaces (29, 59, 59') being precisely coupled to each other so that the toothed sleeve (55, 55') is ensured to be centered relative to the flanged hub (20).

2. The unit (10) according to claim 1, characterized in that The cylindrical surface (59) of the toothed sleeve (55) is a discontinuous surface formed by the top surface of the inner groove (56) passing through in the axial direction.

3. The unit (10') according to claim 1, characterized in that The inner groove (56') of the toothed sleeve (55') is delimited in the axial direction by the step (58'), and the cylindrical surface (59') of the toothed sleeve (55') is a continuous surface.

4. The unit (10, 10') according to any one of the preceding claims, characterized in that The cylindrical surface (29) of the tubular portion (50) of the flanged hub (20) is located axially inside relative to the toothed profile (23) and axially outside relative to the end edge (24) of the flanged hub (20).

5. The unit (10, 10') according to any one of the preceding claims, characterized in that The coupling between the cylindrical surface (29) of the tubular portion (50) and the cylindrical surface (59, 59') of the toothed sleeve (55, 55') is indeterminate.

6. The unit (10, 10') according to any one of the preceding claims, characterized in that The diameter (D) of the cylindrical surface (29) 29 ) is smaller than the diameter (D) of the bottom cylindrical surface (23') of the toothed profile (23) of the flanged hub (20) 23' ).

7. The unit (10, 10') according to any one of the preceding claims, characterized in that The diameter (D) of the cylindrical surface (29) 29 ) is greater than the diameter (D) of the radially outer cylindrical surface (24') of the end edge (24) of the flanged hub (20) 24' ).

8. The unit (10') according to claim 7, characterized in that The diameter (D 29 ) and the diameter (D 24' ) is between 0.1mm and 1mm.

9. The unit (10, 10') according to any one of the preceding claims, characterized in that The axial length (L) of the cylindrical surface (59, 59') of the toothed sleeve (55, 55') is equal to at least 1 mm.

10. The unit (10, 10') according to any one of the preceding claims, characterized in that The flanged hub (20) is provided with a radially inner first shoulder (26) and a second shoulder (27), and the unit (10, 10') comprises: - a first radial ball bearing (60) and at least one second radial ball bearing (61), located radially internally with respect to the flanged hub (20) and corresponding to the first shoulder (26) and the second shoulder (27) of the flanged hub (20); the at least one second bearing (61) is mounted in a seat (28), obtained in an axially internal position in the flanged hub (20) and axially delimited by the second shoulder (27); and - a spacer (70) mounted in said seat (28) at an intermediate position between said second axial shoulder (27) and said at least one second bearing (61) and arranged to abut axially against said second shoulder (27).

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