Method for manufacturing a wheel hub bearing unit for a vehicle and associated unit

Abstract

A wheel hub bearing unit (1) comprises an outer ring (2), rolling elements (7) and an inner ring (3), wherein the inner ring is provided with a flange (5) at a first end (4) thereof, the inner ring being provided with a sliding surface (12) for a sealing lip (11) of a sealing device (8) configured to protect the rolling elements, the sliding surface being defined by a metal insert (15), the metal insert being integrally formed with the first end (4) and being configured to span a base (13) of the flange and a portion (14) of the first end (4) immediately adjacent to the base of the flange, the metal insert (15) having a thickness between 0.2 mm and 2 mm, and being made by additive manufacturing using a material different from the material of the inner ring (3) and consisting of austenitic stainless steel.

Description

Technical Field

[0001] The invention relates to a method for producing a wheel hub bearing unit for a vehicle, and to the associated wheel hub bearing unit, which is particularly compact and has an outboard seal (i.e. a seal arranged toward the outside of the vehicle) which has a long service life. An assembly consisting of a flanged inner ring of a rolling bearing of a wheel hub bearing unit for a vehicle also forms part of the invention. Background Art

[0002] As is known, a wheel hub bearing unit of a vehicle generally consists of the following components: a rolling bearing inner ring having a first flanged end; a rolling bearing outer ring mounted on the inner ring on a side opposite to the first flanged end of the inner ring; a plurality of rolling elements arranged between the inner ring and the outer ring so that the inner ring and the outer ring can rotate relative to each other with a small amount of friction; and at least one sealing device arranged to protect the rolling elements on one side of the first flanged end of the inner ring.

[0003] During use, the vehicle wheel is mounted on the flanged end of the inner ring, while the outer ring, which may be more or less flanged, is fixed to / inside a suspension pillar of the vehicle.

[0004] Nowadays, it is particularly urgent to ensure that the sealing lip of a sealing device slides on a smooth and corrosion-resistant surface. For this purpose, the sealing device consists of two facing screens, namely: a first screen carrying an elastomeric element provided with an elastically deformable sealing lip; and a second screen made of stainless steel or a metal sheet lined with a protective material, mounted facing the first screen and mounted on a corresponding sliding surface engaged by the sealing lip.

[0005] This solution is satisfactory, but has a number of disadvantages. Firstly, it is relatively bulky ( / heavy) in the axial direction, while in many applications the available space is limited. The use of a second shield with a complex form only partially solves the problem of axial dimensions, but at a high cost. Secondly, in the case of a solution with two shields, there is a risk of relative movement of the two shields and / or of the two shields relative to the rolling bearing ring, with the result that there is a risk of loss of sealing effect and damage to the rolling elements.

[0006] At this time, removing the second shield will result in direct frictional contact of the sealing lip on the inner ring, with the seal being fastened directly to the outer ring in the area attached by the flange, with the attendant risk of rapid wear of the sealing lip and corrosion of the sliding surface of the sealing lip. Summary of the invention

[0007] The object of the present invention is to provide a method for manufacturing a wheel hub bearing unit for a vehicle and an associated wheel hub bearing unit provided with a flanged inner ring which do not have the disadvantages of the prior art, are reliable and cost-effective and can also reduce the axial size of the wheel hub bearing unit.

[0008] On the basis of the present invention, therefore, there is provided a method for manufacturing a wheel hub bearing unit and an associated wheel hub bearing unit and a flanged inner ring of the unit, having the characteristics indicated in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The invention will now be described with reference to the accompanying drawings which illustrate two non-limiting examples of embodiments of the invention, in which:

[0010] Figure 1 A schematic diagram shows a radial cross-sectional front view of a wheel hub bearing unit for a vehicle according to the present invention, wherein a portion of the wheel hub bearing unit is removed for greater simplification of the illustration;

[0011] Figure 2 shows in schematic form the same radial sectional front view of a wheel hub bearing unit for a vehicle according to a possible variant of the invention, with parts of the wheel hub bearing unit removed for greater simplification of the illustration; and

[0012] Figure 3 Possible alternative embodiments of the invention are shown. DETAILED DESCRIPTION

[0013] Reference Figure 1 , wherein 1 represents a wheel hub bearing unit for a vehicle as a whole, the wheel hub bearing unit comprising a rolling bearing 2, the rolling bearing 2 further comprising: an inner ring 3, a first end 4 of the inner ring 3 being provided with a flange 5 on the radial outside; an outer ring 6; and a plurality of rolling bodies 7, arranged between the outer ring 6 and the inner ring 3, so that the outer ring 6 and the inner ring 3 are relatively rotatable.

[0014] In order to simplify the illustration, the wheel hub bearing unit 1 is only shown schematically and the outer ring 6 and the inner ring 3 are truncated. The wheel hub bearing unit 1 also includes at least one sealing device 8 of a known type, which is integrally mounted on the outer ring 6 and includes a rigid annular screen 9. In radial section, the rigid annular screen 9 is formed as required to have the necessary folded zone required to strengthen the cross-section, for example, in a generally L-shaped form, or as in the non-limiting example of the embodiment shown, in a generally "7" form.

[0015] The rigid annular shield 9 has an elastic annular sealing element 10 integrally mounted thereon, the elastic annular sealing element 10 being provided with a plurality of sealing lips 11 (known per se and elastically deformable), the sealing lips 11 being constructed to engage against and preferably engage in contact with a radially outer sliding surface or mating surface ( / counter-face) of the first end portion 4 of the inner ring 3 to form a friction seal together with the radially outer sliding surface or mating surface (or, in the case where one or more lips 11 engage without contact with the surface 12, to form a labyrinth seal together with the radially outer sliding surface or mating surface).

[0016] According to one aspect of the present invention, the inner ring 3 of the wheel hub bearing unit 1 for a vehicle is made into an integral piece ( / one piece) with the radial outer flange 5 at its first end 4, and a metal insert 15 is also provided between the base portion 13 of the flange 5 and a portion 14 of the first end 4 adjacent to the flange 5, and the metal insert 15 extends across ( / spans) (astride) the base portion 13 of the flange 5 and the portion 14 of the first end 4 of the inner ring 3 adjacent to the base portion 13 of the flange on the same side.

[0017] In this embodiment, the metal insert 15 completely occupies a radially outer recess 16 of the inner ring 3 , which extends radially both outside above the base 13 of the flange 5 and outside above a portion 14 of the first end 4 of the inner ring 3 that is adjacent to the base 13 of the flange 5 .

[0018] According to one aspect of the invention, the metal insert 15 is made of a material different from the material of which the inner ring 3 is made, and in particular, is made of a metal or a metal alloy that is corrosion resistant and has a relatively low friction coefficient.

[0019] According to one aspect of the invention, the sliding surface 12 is defined by a metal insert 15, which is annular in the above-mentioned position and is formed as a single piece with the first end 4 of the inner ring 3 so as to completely occupy the recess 16, which is also annular and is formed on the radially outer surface 18 of the inner ring 3, and on the radially outer surface 18 there is also formed a corresponding raceway 19 for the rolling elements 7 (only one of the raceways is shown, the other raceway is arranged on the known ring component 3 which has been truncated for a simpler illustration).

[0020] The sliding surface 12 defined and delimited by the metal insert 15 forms the radially outer surface of the end 4 and therefore forms part of the lateral surface 18 , forming the portion of the lateral surface 18 closest to the flange 5 .

[0021] The thickness of the metal insert 15 ranges between 0.2 mm and 2 mm, and preferably between 0.4 mm and 0.8 mm, said measurement corresponding to the depth of the recess 16 in this embodiment.

[0022] According to one aspect of the invention, the metal insert is formed of stainless steel, in particular austenitic stainless steel, and even more particularly of austenitic stainless steel containing silicon of a type standardized for welding; for example, according to an embodiment of the invention, the metal insert 15 is made of AISI316L steel having a silicon content equal to about 1% by weight and a low carbon content (necessarily equal to or less than 0.03%). This material represents a preferred but non-limiting embodiment of the invention.

[0023] The Si content of the types standardized for wire welding is more generally between 0.8% and 1% by weight, in order to be able to obtain the metal insert 15 by additive manufacturing.

[0024] Therefore, it is clear from the above that the present invention also relates to a method for manufacturing a wheel hub bearing unit 1 for a vehicle, the wheel hub bearing unit 1 comprising a rolling bearing 2 and at least one sealing device 8, the rolling bearing 2 further comprising an inner ring 3, an outer ring 6 and a plurality of rolling bodies 7, the first end 4 of the inner ring 3 being provided with a flange 5 on the radial outside, the plurality of rolling bodies 7 being arranged between the outer ring and the inner ring so that the inner ring and the outer ring are relatively rotatable, the at least one sealing device 8 being integrally mounted on the outer ring 6 and being provided with a plurality of sealing lips 11, the plurality of sealing lips 11 being constructed to engage by sliding on a radial outer surface 12 of the first end 4 of the inner ring 3.

[0025] The method according to the invention comprises the following steps:

[0026] a) manufacturing the outer ring 6 and the inner ring 3, for example, by making the inner ring 3 and the flange 5 in a rough configuration as a single piece by forging or casting, during which step or subsequently by machining, a radially outer recess 16 is formed on the radially outer surface 18 of the inner ring 3, the radially outer recess 16 being configured to span the base 13 of the flange 5 and the portion 14 of the first end 4 of the inner ring 3 immediately adjacent to the base 13 of the flange 5 on the same side. During this step, the recess 16 is formed to extend both above the base 13 of the flange 5 and above the portion 14 of the first end 4 of the inner ring 3 immediately adjacent to the base 13 of the flange 5;

[0027] b) progressively ( / gradually) filling at least the entire recess 16 with an insert 15, which is made by additive manufacturing of a metal or metal alloy that is corrosion-resistant and has a relatively low coefficient of friction; during this step, the insert 15 may also extend outside the recess 16, for example, the insert 15 may also extend over a portion of the surface 18 or extend heightwise beyond the edge of the surface 18;

[0028] c) machining the metal insert 15 so as to form a sliding surface 12 for the sealing lip 11, the sliding surface 12 being formed to be curved ( / curved surface) and to seamlessly connect the base 13 of the flange 5 to the first end 4 of the inner ring 3 and the base 13 of the flange 5 to a surface 18 flush with the first end 4;

[0029] d) Install the sealing device 8 on the outer ring 6 and the outer ring 6 on the side opposite to the flange 5 on the inner ring 3 with the rolling elements 7 arranged between the outer ring 6 and the inner ring 3 so that the sealing lip 11 cooperates with the sliding surface 12 .

[0030] The metal insert 15 is preferably produced by means of the SLM (Selective Laser Manufacturing) technique and in any case using a metal material in powder form having an average grain size of 90 microns.

[0031] The metal insert 15 is made of stainless steel.

[0032] The metal insert is made in particular from austenitic stainless steel.

[0033] The metal insert is even more particularly made of stainless steel AISI 316L of a type standardized for welding, with a Si content ranging between 0.8% and 1%.

[0034] Finally, the metal insert 15 is produced in the finished state and therefore after machining, in the region of the sliding surface 12, with a thickness of between 0.2 mm and 2 mm and preferably between 0.4 mm and 0.8 mm, said measurements being made at Figure 1 In the embodiment shown, this corresponds to the depth of the recess 16 .

[0035] Now refer to Figure 2 , in which, for the sake of simplicity, details similar to or identical to those already described are represented by the same figure numbers, the figure shows a wheel hub bearing unit 100 for a vehicle, the wheel hub bearing unit 100 includes a rolling bearing 2, the rolling bearing 2 includes: an inner ring 3, a first end 4 of the inner ring 3 is provided with a flange 5 on the radial outside; an outer ring 6; and a plurality of rolling bodies 7, which are arranged between the outer ring 6 and the inner ring, so that the outer ring 6 and the inner ring 3 are relatively rotatable.

[0036] In this case, the recess 16 is also formed radially outside the side on which the lateral surface 18 is located, but it extends over the entire base 13 of the flange 5 until it is substantially flush with the radially outer surface 20 of the outer ring 6 .

[0037] The recess 16 is occupied by a metal insert 150 which completely fills the recess 16 and which, unlike the insert 15, is progressively deposited by additive manufacturing in the manner already described so as to extend axially and radially outside the recess 16. The insert 150 is then machined to form the sliding surface 12 and in addition a projection 151 is formed on the base 13 of the flange 5, the projection 151 being configured to extend axially inside the outer ring 6 and radially inside the outer ring 6, on the outside of the radially outermost sealing lip 11, radially adjacent to and parallel to the sealing lip 11. The projection 151 can also be formed directly by additive manufacturing already in its determined form and configuration, without machining.

[0038] The protrusion 151 defines and forms together with the radially outer lip 11 and with the shield 9 a further labyrinth seal 152 which is arranged radially outside the other radially innermost lip and radially outside the sliding surface 12 to protect it.

[0039] The deposition of metal can meet the market demand for sealing lips sliding on stainless steel materials and use a more compact and low-cost sealing design.

[0040] Further advantages may be obtained where deposition of material may be used to create the labyrinth 152 for the seal.

[0041] Now refer to Figure 3 , in which, for the sake of simplicity, details similar to or identical to those already described are represented by the same figure numbers, the figure shows a wheel hub bearing unit 200 for a vehicle, the wheel hub bearing unit 200 includes a rolling bearing 2, and the rolling bearing 2 includes: an inner ring 3, a first end 4 of the inner ring 3 is provided with a flange 5 on the radial outside; an outer ring 6; and a plurality of rolling bodies 7, which are arranged between the outer ring 6 and the inner ring, so that the outer ring 6 and the inner ring 3 are relatively rotatable.

[0042] However, in this case, there is no recess 16, but a metal insert 1500 is provided which, however, is located directly on the radially outer surface 18, both externally above the base 13 of the flange 5, extending radially and extending to a point substantially as far as flush with the radial outer surface 20 of the outer ring 6, and externally above the entire portion 14 of the first end 4 of the inner ring 3 that is adjacent to the flange 5, extending radially and, in the example shown, extending towards the raceway 19.

[0043] The insert 1500 is progressively deposited on the side surface 18 (or part thereof) by additive manufacturing in the manner already described, so as to extend axially and radially on the outside of the flange 5 and the portion 14 (directly on the rough-formed or previously machined side surface 18). The insert 1500 is then machined to form the sliding surface 12.

[0044] During this step, according to another possible variant that is not shown, a groove for the insert 1500 may also be formed opposite the base 13 of the flange 5 as described above. Figure 2 The protrusion 151 can also be formed directly by additive manufacturing already in its determined form and configuration, then only additionally requiring finishing in the same way as the entire insert 1500. In all the embodiments described, the inserts 15, 150 and 1500 are obtained by laser additive manufacturing using metal powders with an average particle size between 70 and 100 microns and preferably equal to 90 microns, applying a laser power of 400 Watts and a relative translation speed of the laser to the machining surface equal to 10 mm / s until a "rough" insert with a minimum thickness of 0.5 mm is obtained.

[0045] Since without machining the insert 15, 150, 1500 would not have a surface finish suitable for forming the sliding surface 12, after its deposition and cooling, the insert 15, 150, 1500 is machined again until it has a working thickness between 0.2 mm and 2 mm.

[0046] Therefore, the described solution offers the following advantages:

[0047] 1) It is possible to use the well-known compact sealing design which previously did not work due to the high corrosion of the surface of the lip of the sealing device formed by a single shield;

[0048] 2) Obtaining a labyrinth 152 formed in the inner ring 3 of the flange, avoiding any type of handling, assembly and position control;

[0049] 3) The coating can be applied completely freely due to the absence of silicon particles, which in known double shield seal designs are caused by the need to arrange silicon paste between the shield mounted on the inner ring 3 and the ring itself to increase the sealing effect.

[0050] Thus, all objects of the invention are achieved.

Claims

1. A method for manufacturing a wheel hub bearing unit (1; 100) for a vehicle, the wheel hub bearing unit comprising a rolling bearing (2) and at least one sealing device (8), the rolling bearing (2) further comprising an inner ring (3), an outer ring (6) and a plurality of rolling bodies (7), the first end (4) of the inner ring (3) being provided with a flange (5) on the radial outside, the plurality of rolling bodies (7) being arranged between the outer ring and the inner ring so that the outer ring and the inner ring are relatively rotatable, the at least one sealing device being integrally mounted on the outer ring and being provided with a plurality of sealing lips (11), the plurality of sealing lips being configured to engage on a radial outer surface (12) of the first end of the inner ring; characterized in that The method comprises the following steps: a) manufacturing the outer ring (6) and the inner ring (3), and manufacturing the inner ring (3) and the flange (5) as an integral part; b) progressively forming an insert (15; 150; 1500) on the radially outer surface (18) of the inner ring, the insert being made by additive manufacturing of a corrosion-resistant metal or metal alloy having a relatively low coefficient of friction; the insert (15; 150; 1500) being configured to span the base (13) of the flange and a portion (14) of the first end (4) of the inner ring immediately adjacent to the base of the flange on the same side, the insert extending both above the base (13) of the flange and above the portion (14) of the first end (4) of the inner ring immediately adjacent to the base of the flange; c) machining the insert (15; 150) so as to form a sliding surface (12) for the sealing lip (11), the sliding surface (12) being curved and seamlessly connecting the base (13) of the flange to the first end (4) of the inner ring; d) mounting the sealing device (8) on the outer ring (6), and mounting the outer ring on the inner ring at a side opposite to the flange (5) and arranging a rolling body (7) between the inner ring and the outer ring, so that the sealing lip (11) cooperates with the sliding surface (12).

2. The method according to claim 1, characterized in that: During step a), a recess (16) is also formed on the radially outer surface (18) of the inner ring, the recess (16) being configured to span the base (13) of the flange and a portion (14) of the first end (4) of the inner ring immediately adjacent to the base of the flange on the same side, the recess (16) extending both above the base (13) of the flange and above the portion (14) of the first end (4) of the inner ring immediately adjacent to the base of the flange; and Step b) is performed by forming the insert (15; 150; 1500) directly inside the recess (16) by means of additive manufacturing until the insert at least completely fills the recess (16), optionally, step b) is performed by forming the insert (15; 150; 1500) directly inside the recess (16) by means of additive manufacturing until the insert overflows axially and / or radially to protrude from the recess (16).

3. The method according to claim 1 or 2, characterized in that: The insert (15; 150) is manufactured by selective laser manufacturing (SLM) technology using metal powder with an average particle size between 70 microns and 100 microns and applying a power of 400 W and a relative translation speed of 10 mm / sec.

4. The method according to claim 1 or 2, characterized in that: The insert (15; 150; 1500) is made of stainless steel.

5. The method according to claim 4, characterized in that The insert (15; 150; 1500) is made of austenitic stainless steel.

6. The method according to claim 4, characterized in that The insert (15; 150; 1500) is made of stainless steel AISI316L of a standardized type for welding with a Si content ranging between 0.8% and 1%.

7. The method according to claim 1 or 2, characterized in that: The insert (15; 150; 1500) has a minimum thickness of 0.5 mm after its application step and a thickness of between 0.2 mm and 2 mm after machining.

8. The method according to claim 1 or 2, characterized in that: The insert (15; 150; 1500) has a minimum thickness of 0.5 mm after its application step and a thickness of between 0.4 mm and 0.8 mm after machining.

9. A wheel hub bearing unit (1; 100; 200) for a vehicle, comprising a rolling bearing (2) and at least one sealing device (8), wherein the rolling bearing (2) further comprises an inner ring (3), an outer ring (6) and a plurality of rolling bodies (7), wherein a first end (4) of the inner ring (3) is provided with a flange (5) on the radially outer side, the plurality of rolling bodies (7) are arranged between the outer ring and the inner ring so that the outer ring and the inner ring are relatively rotatable, and the at least one sealing device is integrally mounted on the outer ring and provided with a plurality of sealing lips (11), wherein the sealing lips (11) are configured to engage against a radially outer sliding surface (12) of the first end (4) of the inner ring; characterized in that The sliding surface (12) is defined by a metal insert (15; 150; 1500) formed integrally with the first end (4) of the inner ring as a single piece, the metal insert (15; 150; 1500) being configured to span on the same side the base (13) of the flange and a portion (14) of the first end of the inner ring immediately adjacent to the base (13) of the flange, the thickness of the metal insert (15; 150; 1500) being between 0.2 mm and 2 mm; the metal insert (15; 150; 1500) being made of a material different from the material of which the inner ring is made and consisting of a metal or metal alloy that is corrosion-resistant and has a relatively low coefficient of friction.

10. The wheel hub bearing unit according to claim 9, characterized in that: The metal insert (15; 150; 1500) completely occupies a recess (16) of the inner ring, which extends both over the base (13) of the flange and over a portion (14) of the first end of the inner ring that is adjacent to the base (13) of the flange.

11. The wheel hub bearing unit according to claim 9 or 10, characterized in that: The metal insert (15; 150; 1500) is made of stainless steel.

12. The wheel hub bearing unit according to claim 9 or 10, characterized in that: The metal insert is made of austenitic stainless steel.

13. The wheel hub bearing unit according to claim 9 or 10, characterized in that: The metal insert (15; 150; 1500) is made of stainless steel AISI316L of a standardized type for welding with a Si content ranging between 0.8% and 1%.

14. An inner ring (3) of a rolling bearing (2), the inner ring being made in one piece with a radial outer flange (5) at its first end (4), characterized in that: A metal insert (15; 150; 1500) is provided between the base (13) of the flange and a portion (14) of the first end (4) of the inner ring adjacent to the flange (5), the metal insert extending across the base (13) of the flange and a portion (14) of the first end of the inner ring adjacent to the base of the flange on the same side, the thickness of the metal insert (15; 150; 1500) being between 0.2 mm and 2 mm; the metal insert (15; 150; 1500) being made of a material different from the material of which the inner ring (3) is made and consisting of austenitic stainless steel.

15. The inner ring (3) of the rolling bearing (2) according to claim 14, characterized in that: The inner ring (3) of the rolling bearing (2) is the inner ring of a wheel hub bearing unit (1; 100) for a vehicle.

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