Wheel hub bearing unit for motor vehicle wheels

Abstract

The hub bearing unit (10) has a rotation axis (X), a radially outer stationary ring (31), a radially inner flange hub (20), a first radial ball bearing (59), and at least one second radial ball bearing (60). The flange hub (20) is provided with first and second shoulders (25a, 27a) and a first relief groove (29). The flange hub engages with the rod portion (50b) of a constant velocity universal joint (50) via the two bearings (59, 60), thereby allowing the flange hub (20) to rotate relative to the rod portion (50b). The second radial ball bearing (60) is fitted into a seat bore (28) on the side of the flange hub (20) near the constant velocity universal joint (50). The unit (10) also includes a spacer (70) fitted into the seat bore (28) between the second shoulder (27) and at least one second radial ball bearing (60). A second slow-release groove (80) is provided in the seat hole (28), located on the axial outer side of the narrow section (SR) opposite to the position of the first slow-release groove (29) of the flange hub (20).

Description

Technical Field

[0001] This invention relates to a hub bearing unit for a wheel of a motor vehicle. In particular, the hub bearing unit includes a bearing unit capable of disengaging a constant velocity joint, thus making it suitable for use on both drive and driven wheels, i.e., for motor vehicles with engageable four-wheel drive. The bearing unit rotatably supports the vehicle's wheel on the suspension, while the constant velocity joint mechanically connects to the vehicle's drive axle. Background Technology

[0002] It is well known and widely used that wheel hub bearing units include bearing units for rotatably supporting the wheel on the suspension. Although such bearing units generally contain only a pair of rolling bearings, it is also known that bearing units to which the present invention can be applied have different structures.

[0003] According to existing technology, a wheel hub bearing unit comprises a rotatable flanged hub (i.e., a "flared hub") that mechanically connects to rotating components of a motor vehicle (e.g., discs of wheels or brake components). The bearing unit includes an outer ring, a pair of inner rings, and a plurality of rolling elements, such as balls (commonly known as "ball bearings"). One of the pair of inner rings may be the flanged hub itself. All these components have an axisymmetric shape relative to the axis of rotation of the rotating component (e.g., the flanged hub and the inner rings of the bearing unit).

[0004] The flange hub receives drive torque from the bell of the constant velocity joint via a grooved joint. Specifically, the bell of the constant velocity joint has external axial teeth, and a toothed rim with external axial teeth is also fixed to the hub (hence also referred to below as the "hub toothed rim"). A toothed rim with internal axial teeth transmits motion from the universal joint to the hub; this rim is equipped with a system for disengaging from the hub toothed rim. Therefore, when the rim engages with the hub toothed rim, motion transmission from the drive axis to the vehicle wheel occurs, and the wheel thus operates as a drive wheel; conversely, when the rim disengages from the hub toothed rim, motion transmission from the drive axis to the wheel is interrupted, and the wheel operates as a driven wheel.

[0005] In this configuration, a bearing is required between the hub and the constant velocity joint (CV joint) to allow the hub to rotate independently. Typically, these bearings are radial ball bearings (also known as "radial ball bearings").

[0006] Therefore, a hub bearing unit with a drive shaft clutch system requires a combination of an internally hollow flange hub and two (or more) radial ball bearings located radially inside the flange hub. Furthermore, the axially inner radial ball bearings also require axial shoulders to define the axial position of the constant velocity joint relative to the hub bearing unit.

[0007] Machining the seat of the axially inner radial ball bearing inside the flange hub requires a relief groove located near the axial shoulder.

[0008] This requirement, along with the shape and location of the relief groove formed directly in the flange hub and the narrow portion of the flange hub formed in the same area (the narrow portion originating from the need to machine the tooth profile for engagement between the flange hub and the gear ring), results in high stress concentration and low fatigue wear of the components within the area of ​​the relief groove.

[0009] Therefore, it is necessary to provide a new design for the hub bearing unit so that the hub bearing unit does not have the above-mentioned disadvantages, or at least significantly reduces the above-mentioned disadvantages. Summary of the Invention

[0010] To fully address the aforementioned technical problems, one object of the present invention is to provide a hub bearing unit for connection to a system for disconnecting a drive shaft. The hub bearing unit's flange hub is provided with a radially inner spacer that functions to provide an axial shoulder for a radial ball bearing. Using the spacer to provide an axial shoulder for the radial ball bearing allows the flange hub to achieve a different internal shape. In practice, the relief groove for machining the flange hub can be formed axially outside the spacer, thus in a lower stress region of the flange hub, and in any case, sufficiently far from the narrow (and therefore most critical) portion of the flange hub. To reduce stress concentration, greater design freedom can also be adopted, thus providing an elongated (relief) groove with a larger radius.

[0011] Therefore, the present invention proposes a hub bearing unit having the distinguishing features defined in the independent technical solutions appended to this specification.

[0012] Further preferred and / or particularly advantageous embodiments of the invention are described in accordance with the distinguishing features in the accompanying dependent technical solutions. Attached Figure Description

[0013] The present invention will now be described in conjunction with the accompanying drawings, which illustrate specific embodiments of the invention and are non-limiting examples.

[0014] Figure 1 The diagram shows a cross-sectional view of a hub bearing unit provided with a (clutch) system adapted to disengage (disconnect) from the drive shaft, according to one embodiment of the present invention.

[0015] Figure 2 According to Figure 1 Detailed enlarged view of the wheel hub bearing unit; and

[0016] Figure 3 According to Figure 1 A further enlarged view of the details of the radially inner relief groove of the flange hub of the wheel hub bearing unit; Detailed Implementation

[0017] The present invention will now be described by way of non-limiting embodiments, with reference to a motor vehicle wheel hub bearing unit provided with a bearing unit.

[0018] See Figure 1 The number 10 refers generally to the hub bearing unit according to a preferred embodiment of the present invention. These figures show details of an example structure.

[0019] The wheel hub bearing unit 10 is positioned between the vehicle's wheels and chassis (both are known and therefore not shown) during use, and can be selectively connected to the constant velocity joint 50 via a known transmission device 90. The transmission device 90 is used to transmit drive torque to the corresponding wheel (not shown), or to block the transmission of drive torque to the corresponding wheel.

[0020] The hub bearing unit 10 includes a rotatable flange hub 20 and a bearing unit 30 having a central axis of rotation X. The bearing unit 30 further includes:

[0021] - Radial outer stationary ring (hereinafter referred to as "radial outer ring") 31; and

[0022] - A radial inner ring 20 defined by a flange hub 20, which is rotatable relative to a radial outer ring 31, because two rows of rolling elements 32, 33 (balls in this example) are provided between them.

[0023] The constant velocity universal joint 50 comprises a bell 50a and a stem 50b. The bell 50a is arranged near the flange hub 20 and has radially outward axial teeth 51. The stem 50b is integral with the bell 50a and, as fully described below, is mounted via the flange hub 20 such that it is axially locked in a generally known manner by a threaded annular nut 50c.

[0024] Throughout this specification and the claims, terms and expressions characterizing position and orientation, such as “radial” and “axial,” should be understood to be relative to the central rotation axis X of the bearing unit 30. Furthermore, expressions such as “axially outer” and “axially inner”, under the assembly conditions of the wheel hub bearing unit, preferably refer to the side where the wheel is located and the side opposite to the wheel, respectively, in the specific case to be discussed.

[0025] For the purpose of simplifying the illustrations, the numerals 32 and 33 are used to refer to both individual balls and rows of balls. Similarly, for the purpose of simplification, the term "ball" is used in this specification and accompanying drawings in an illustrative manner instead of the more general term "rolling body" (therefore, the same numerals are also used to refer to rolling bodies).

[0026] The flange hub 20 has a central through-hole 20f extending along the axis X such that it is engaged by the rod portion 50b. The flange hub 20 includes a flange 25 located axially outward for securing a hub bearing unit to the wheel and a rolled edge 24 located axially inward near the constant velocity joint 50. The rolled edge 24 is configured to apply a preload axially to both the inner ring 34 and a toothed ring 52 mounted on the inner ring 34 from the outside of the rolled edge 24. The toothed ring 52, together with the radially outer axial teeth 51 of the bell-shaped body 50a, forms part of a transmission device 90. The transmission device 90 is configured to selectively transmit the drive torque provided by a drive shaft (not shown, as is known) angularly engaged with the constant velocity joint 50 and includes a toothed rim 53 with inner axial teeth. The tooth 53 can selectively engage either solely with the axial tooth 51, allowing the hub bearing unit 10 to idle, or simultaneously with both the axial tooth 51 and the gear ring 52, angularly locking the bell-shaped body 50a to the flange hub 20. Therefore, when the tooth 53 engages with the gear ring 52 on the flange hub 20, motion transmission from the drive axis to the wheel occurs, and the wheel thus operates as a drive wheel; conversely, when the tooth 53 disengages from the gear ring 52 on the flange hub 20, motion transmission from the drive axis to the wheel is interrupted, and the wheel thus operates as an idle wheel or a driven wheel.

[0027] It should be noted that this invention relates only to the wheel hub bearing unit 10 and not to motion transmission components (drive shaft, constant velocity joint, wheels of motor vehicles). Therefore, these motion transmission components are not described or shown in the accompanying drawings.

[0028] like Figure 2 As shown, in a structure where the flange hub 20 disengages from the bell-shaped body 50a of the constant velocity universal joint, allowing it to rotate independently of the constant velocity universal joint, a bearing is required between the flange hub 20 and the rod portion 50b of the constant velocity universal joint 50. In embodiments of the present invention, as... Figure 1As can be seen, the flange hub 20 has a first shoulder 25a and a second shoulder 27 formed radially inside the central through hole 20f. Adjacent to these two shoulders 25a and 27 are two radial ball bearings 59 and 60, respectively. These two radial ball bearings 59 and 60 are mounted radially inside the flange hub 20 and radially outside the constant velocity universal joint rod portion 50b. Specifically, the first radial ball bearing 59 is mounted axially outside, abutting against the first shoulder 25a; the second radial ball bearing 60 is mounted axially inside (i.e., towards the bell-shaped body 50a of the constant velocity universal joint 50), abutting against the second shoulder 27.

[0029] According to the present invention, the axial stop of the second radial ball bearing 60 (necessary for defining the axial position of the constant velocity universal joint relative to the hub bearing unit) is achieved by a shim 70. The shim 70 is located radially inside the flange hub 20 and axially outside the radial ball bearing 60. Thus, the shim 70 is axially locked against the second axial shoulder 27 of the flange hub 20.

[0030] More precisely, the annular nut 50c clamps the two radial bearings 59, 60 and the spacer 70 onto the shoulders 25a, 27, applying axial pressure to the flange hub 20 through the outer rings of the bearings 59, 60 and the spacer 70. The hub 20, following the stress transmitted from the wheel, generates a reaction force on the shoulders 25a, 27, especially the second shoulder 27 on the axially inner side, because the second shoulder 27 is located at the position of the radial section SR of the flange hub 20, which has a relatively small thickness. In fact, this radial section SR is located opposite the radially outer relief groove 29 of the flange hub 20, and is necessary for machining the toothed profile for the engagement between the flange hub 20 and the gear ring 52, thus necessarily having a relatively small thickness.

[0031] From a tension perspective, the presence of the shim 70 improves the geometry of the flange hub 20. In fact, to enable grinding of the radially inner seat 28 of the flange hub 20 (i.e., the seat accommodating the second radial ball bearing 60 and the shim 70), a relief groove 80 needs to be defined between the seat 28 and the second axial shoulder 27. This relief groove 80 is therefore located axially outside the seat 28 and radially inside the entire flange hub 20. However, due to the presence of the shim 70, the relief groove 80 can be formed sufficiently far from the narrow radial section SR of the flange hub 20 (which is the most critical part from a tension perspective). By doing so, the relief groove 80 can be formed with greater design freedom, for example, having a sufficiently large radius R, without causing stress concentration near the narrow section SR of the flange hub 20.

[0032] Therefore, the pad 70 is introduced as an axial shoulder for the axial inner radial ball bearing 60, and its main purpose is to form a radial inner relief groove 80 that is different in shape and position from the case without the pad 70.

[0033] This solves various key structural problems. In fact, without the spacer, the radially inner relief groove 80 would be positioned opposite the radial ball bearing 60, thus its axial position would "face" the radially outer relief groove 29. Furthermore, with the radially inner relief groove formed opposite the radial ball bearing, its shape would be determined by the geometry of the radial ball bearing, resulting in a very limited axial length and radius (e.g., an axial length on the order of 2 mm and a radius on the order of 0.8 mm). All of this would result in a very narrow cross-section SR of the flange hub, and a notch effect due to the presence of the radially inner relief groove.

[0034] Because the flange hub is subjected to high bending loads in this area, high stress is generated, which adversely affects the service life of the flange hub.

[0035] On the other hand, the introduction of pad 70 offers several advantages:

[0036] • The radially inner slow-release groove 80 is formed at a position relative to the axially outer side, and is therefore located relatively far from the radially outer slow-release groove 29 and the narrow section SR;

[0037] • The geometry of the slow-release groove 80 is characterized by a wider radius and a larger overall length, which reduces the nicking effect;

[0038] • If required by the application, a second axially inner radial ball bearing can be introduced without changing the flange hub, and set up in parallel with the first axially inner radial ball bearing, only reducing the axial dimension of the pad 70. The second axially inner radial ball bearing can be used when a single axially inner radial ball bearing is insufficient to withstand the stress from the constant velocity universal joint.

[0039] See further Figure 3 To optimize the slow-release tank 80 and eliminate structural problems of the flange hub, the main geometric parameters are as follows:

[0040] - Geometry of the slow-release tank: The radius R of the slow-release tank 80 should preferably be between 1.8 mm and 2.2 mm, and the variation range of its axial length L can preferably be between 3.8 mm and 4.2 mm.

[0041] - Axial position of the slow-release groove 80: To avoid critical structural problems, the extreme positions of the slow-release groove 80 on the inner and outer sides of the axial direction can be determined under favorable conditions. In particular, the extreme position of the inner side of the slow-release groove 80 can correspond to the projection of the pressure center C between the rolling element 33 and the raceway 34' of the radial inner ring 34 onto the rotation axis X, since the force from the external load is largely transmitted to this area.

[0042] Furthermore, the extreme position of the release groove 80 on the axially outer side can be defined as a distance D ranging from 2.4 mm to 2.6 mm from the surface 24a that abuts against the flange hub 20 and the radial inner ring 34 on the axially inner side. This design avoids alignment between the release groove 80 and the abutment surface 24a of the flange hub 20, as well as the adjacent concave chamfer 24b, thus, as the structural analysis has shown, not increasing the tension of the chamfer 24b within its inner radius RA region.

[0043] Therefore, the axial position of the slow-release tank 80 will be in Figure 2 The section RP, marked with a double-headed arrow, is defined by the two extreme positions mentioned above.

[0044] The solution proposed in this invention essentially solves a critical structural problem that negatively impacts the service life of wheel hub bearing units. Furthermore, due to reduced mechanical stress, the same wheel hub bearing unit can be used in similar but higher-load applications. A further advantage is that the release groove region does not require local heat treatment, thus offering process and related cost advantages. Finally, the solution is conceivably flexible, as two axially inner radial ball bearings can be embedded by changing the length of the spacer without modifying the flange hub design. Therefore, the decision regarding the use of one or two axially inner ball bearings, in addition to the axially outer radial ball bearings, can obviously be made at any stage of development without requiring design changes to the flange hub.

[0045] It must be understood that numerous other variations of the invention exist besides the specific embodiments described above. It should also be understood that these embodiments are merely examples and do not limit the scope of protection of the invention, nor its application or possible constructions. Rather, while the above description allows those skilled in the art to practice the invention according to at least one embodiment, it must be understood that many variations of the described components are possible according to their literal meaning and / or their legal equivalents, without departing from the scope of the invention as defined in the appended claims.

Claims

1. A hub bearing unit (10) having a rotation axis (X), comprising: -Radial outer stationary ring (31); - A radially inner flange hub (20), which is rotatable relative to the axis (X) and the stationary ring (31), engages axially with the rod portion (50b) of the constant velocity universal joint (50), and is provided with a first shoulder (25a) and a second shoulder (27) located on the radially inner side and a first release groove (29) located on the radially outer side. - A first radial ball bearing (59) and at least one second radial ball bearing (60) are located between the rod portion (50b) and the flange hub (20), opposite to a first shoulder (25a) and a second shoulder (27), thereby allowing relative rotation between the flange hub (20) and the rod portion (50b); the at least one second radial ball bearing (60) is mounted in a seat hole (28) formed in the flange hub (20) near the axially inner side of the constant velocity universal joint (50), which is axially defined by the second shoulder (27); It is characterized by a combination of the following features: The hub bearing unit (10) includes a pad (70) mounted in the seat bore (28) at a midpoint between the second shoulder (27) and the at least one second radial ball bearing (60), the pad (70) being configured to axially abut against the second shoulder (27); and The seat hole (28) is provided with a second slow-release groove (80), which is formed on the axial outer side of the narrow section (SR) opposite to the position of the first slow-release groove (29) of the flange hub (20).

2. The hub bearing unit (10) according to claim 1, characterized in that: The radius of the second slow-release tank (80) is between 1.8 mm and 2.2 mm.

3. The hub bearing unit (10) according to claim 1 or 2, characterized in that: The axial length (L) of the second slow-release tank (80) is between 3.8 mm and 4.2 mm.

4. The hub bearing unit (10) according to any one of the preceding claims, characterized in that: The second release groove (80) at its extreme position on the inner side of the axial direction corresponds to the projection of the pressure center (C) between the rolling element in the rolling element row (33) and the raceway (34') of the radial inner ring (34) onto the rotation axis (X) of the hub bearing unit (10).

5. The hub bearing unit (10) according to any one of the preceding claims, characterized in that: The second release groove (80) has a distance (D) in the axial outer limit position between the axial inner side and the surface (24a) of the flange hub (20) that abuts against the radial inner ring (34) located thereon from the axial outer side, which is within a range of 2.4 mm to 2.6 mm.

6. The hub bearing unit (10) according to any one of the preceding claims, characterized in that: The number of the second radial ball bearing (60) located on the inner side of the axial direction is one.

7. The hub bearing unit (10) according to any one of claims 1 to 5, characterized in that: There are two second radial ball bearings (60) located on the inner side of the axis, and the axial dimension of the pad (70) is reduced accordingly due to the increase in the axial dimension of the second radial ball bearing (60).

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