IT201800006111A1 - FLANGED INTERNAL RING OPTIMIZED FOR ORBITAL DEFORMATION OPERATION - Google Patents

Description

Description accompanying a patent application for industrial invention entitled: FLANGED INTERNAL RING OPTIMIZED FOR ORBITAL DEFORMATION OPERATION

DESCRIPTION

Technical sector of the invention

The present invention relates to a flanged inner ring of a rolling bearing belonging to a wheel hub assembly and optimized to improve orbital deformation processing.

The present invention is particularly suitable, although not exclusively, for motor vehicle wheel hub assemblies, assemblies provided with a rolling bearing. These applications include both the case in which the outer ring of the bearing is rotating while the inner ring of the bearing is fixed, and the opposite case in which the inner ring rotates and the outer ring is fixed. The invention is also suitable for any type of rolling bodies (balls, rollers, tapered rollers, etc.).

Known technique

With reference to Figure 1, an example of a wheel hub assembly 1 according to the known art is illustrated. In various applications of wheel hub assemblies 1, the hub 2 has a cylindrical body 3 and an axially external flange portion 4 for connection to the hub. The hub constitutes one of the rotating elements of the bearing unit and is configured to also assume the function of the bearing internal rolling ring. For these reasons, such a hub is also called a flanged inner ring and in the course of the present description it will be indicated in either of the two ways.

Normally, the bearing units of a wheel hub assembly are provided with two raceways 5, 6 of rolling bodies. These bodies roll on respective raceways 7 'of an outer ring 7, in most cases stationary, and on respective raceways 2', 8 'of the inner rings, in most cases rotating.

As stated, the hub assumes the function of an internal ring, in an axially external position, while a second internal ring 8, separated from the hub, is mounted on the hub itself and in particular on a radially external surface 2 ”thereof.

The hub 2 defines in its axially internal end a rolled edge 9 which is configured to axially preload the internal ring 8, after being deformed by means of a plastic processing, called orbital deformation. The rolled edge 9 is shown in an undeformed configuration, with a full line, and in a deformed configuration, with a discontinuous line.

The orbital deformation processing is carried out by means of a tool, schematized in figure 1 and indicated as a whole with 100, which has a cylindrical body 101, an annular press portion 102, with a pressing surface 103 which has an opening angle γ , formed between the pressing surface 103 and a flat surface 104 of the tool 100, radially internal with respect to the pressing surface 103, which assumes values close to 90 ° and in any case greater than 45 °.

Once the orbital deformation processing has been carried out, the radially external diameter DK of the inner ring 8 significantly increases in size due to the effect of the processing itself. In fact, in order to achieve the desired deformation of the edge and the consequent preload on the internal ring 8, the press tool must exert a very high load on the rolled edge of the hub or internal flanged ring and this naturally impacts both the stress state , both on the deformation of the inner ring 8 and consequently on the dimensions of its diameter DK which therefore tend to increase.

There is therefore the need to design an internal flanged ring of a wheel hub assembly and the related tool to achieve the orbital deformation that are free from the aforementioned drawbacks. In particular, there is a need to reduce the amount of force necessary to obtain the deformation of the rolled edge 9 of the flanged inner ring 2 and, consequently, to obtain a lower deformation of the inner ring 8.

Summary of the invention

The purpose of the present invention is to create a flanged inner ring to reduce the deformation of the small inner ring of the bearing unit of a wheel hub assembly, deformation induced by the orbital deformation process performed on the rolling edge of the flanged inner ring itself.

Another purpose of the present invention is to allow the reduction of the rolling force necessary to deform the rolling edge of the flanged inner ring.

The proposed solution provides on the one hand an optimization of the shape of the internal hole of the rolling edge of the flanged internal ring and on the other a consequent optimization of the pressing surface of the tool that carries out the orbital deformation process. This double optimization allows to reduce the amount of energy necessary for the plastic deformation and the percentage increase of the radially external diameter of the small inner ring, that is its overall deformation.

Therefore, according to the present invention, a flanged ring of a wheel hub assembly provided with a rolling edge optimized for the conical orbital deformation operation and having the characteristics set out in the independent product claim, annexed to this description, is described.

Further preferred and / or particularly advantageous embodiments of the invention are described according to the characteristics set forth in the attached dependent claims.

Brief description of the drawings

The invention will now be described with reference to the attached drawings, which illustrate some non-limiting examples of implementation, in which:

- Figure 1, in partial axial symmetrical section, shows the orbital deformation operation of an internal flanged ring according to the known technique,

Figure 2, in partial axial symmetrical section, shows a detail of an assembled wheel hub unit, after carrying out orbital deformation machining according to an embodiment of the present invention,

- Figure 3 is an axial symmetrical section of a flanged inner ring according to an embodiment of the present invention, before the orbital deformation operation,

- Figure 4 is a detail of the rolling edge of the flanged ring in Figure 3,

- Figure 5 is a section of the tool for orbital deformation according to an embodiment of the present invention, and - Figure 6 is a detail of the geometry of the tool in Figure 5.

Detailed description

Referring now to Figure 2, a wheel hub assembly, according to a preferred embodiment of the invention, is indicated as a whole with 10. The figure shows a detail of the exemplary configuration. As mentioned in the introduction, the invention is applicable not only to the configuration described below, but more generally to any motor vehicle wheel hub assembly.

The group 10 comprises a hub 20 preferably, but not necessarily, rotatable and a bearing unit 30. The hub 20 is configured to also take on the function of the internal rolling ring of the bearing and for this reason it is also called an internal flanged ring. Throughout this description and in the claims, the terms and expressions indicating positions and orientations such as "radial" and "axial" are understood to refer to the central rotation axis X of the bearing unit 30. Expressions such as "axially external" and " axially internal ", on the other hand, refer to the mounted condition, and in this case, preferably, they refer to a wheel side and, respectively, to a side opposite the wheel side.

The bearing unit 30 comprises a radially outer ring 31, preferably, but not necessarily, stationary, provided with respective radially outer raceways 31 ', at least one radially inner ring 20, 34, rotatable, provided with respective radially inner raceways 20 ', 34' and two crowns of rolling bodies 32, 33, in this example spheres. The axially external ring of rolling bodies 32 is interposed between the radially external ring 31 and the hub 20 with the function of a radially internal ring, while the axially internal ring of rolling elements 33 is interposed between the radially external ring 31 and the radially inner ring 34. For simplicity of graphical representation, the references 32, 33 will be attributed both to the individual spheres and to the crowns of spheres. Again for simplicity, the term "sphere" can be used as an example in this description and in the attached drawings instead of the more generic term "rolling body" (and the same numerical references will also be used). It will always be understood that any other rolling body can be used instead of the balls (for example, rollers, tapered rollers, rollers, etc.).

The raceways of the crowns 32, 33 are held in position by corresponding cages 39, 40.

The hub 20 defines in its axially internal end a rolled edge 22 which is configured to axially preload the internal ring 34, which is mounted on a radially external surface 20 "of the hub.

With reference to Figure 3, the hub 20 also has an axially external flange portion 23. The flange portion has a plurality of axial fixing holes 24. These holes are the seats for as many fixing means (for example stud bolts, also of a known type) which connect in a known way an element of the motor vehicle wheel, for example the brake disc (also of a known type and not shown in the figure), at the hub 20.

Figure 3 also shows the rolling edge 25 in the non-deformed configuration, ie before being subjected to the orbital deformation processing. For greater clarity, in the present description we indicate as the rolling edge 25 the axially internal edge of the flanged ring 20 in the non-deformed configuration, while we indicate as the rolled edge 22, the same edge in the deformed configuration, i.e. after having been subjected to deformation processing orbital.

Figure 4 is the detail Y of Figure 3. In this figure the rolling edge 25 is represented on an enlarged scale. DK of the radially inner ring 34 due to the deformation induced by the rolled edge 22 and a lower rolling force - said rolled edge 25 has been optimized.

The rolling edge 25 is delimited radially outwards by a mounting surface 20 ", on which the ring 34 is mounted, and is delimited radially inwards by a conical surface 27, which, widening at the outlet from a internal hole 26 of the hub 20 determines a progressive thinning of a radial thickness of the rolling edge 25 itself. The taper of the conical surface 27 allows, first of all, to deform the rolling edge 25 starting from sections with a lower radial thickness, therefore more malleable, or more easily machined by cold deformation, to progressively reach sections of greater radial thickness, therefore, it also allows to break down an axial thrust along the X axis of the forming tool essentially into two components:

- a radial component Cr directed perpendicular to the X axis, e

- an axial component Ca directed along the X axis.

Both the Cr and Ca components are influenced in a first approximation by the value of the angle (shown in Figure 4) of inclination of the taper of the conical surface 27 on which the forming tool acts, and the axial Ca component acts on the rolling edge 25 favoring its deformation and controlling the deformations of the radially inner ring 34.

In fact, due to the conical shape, during the orbital deformation process, the deformation of the rolling edge will proceed starting from the end sections, those with a smaller radial thickness, and progressively arriving at the sections with greater radial thickness. This promotes the flow of material from the undeformed position to the final deformed configuration of the rolling edge. In other words, by reducing the value of the total thrust, the same amount of material will be in contact with the radially internal ring, realizing the retention and preloading function of the ring itself, without deforming it excessively.

Of course, these conditions vary as the amount of material to be deformed varies. Furthermore, the taper value cannot assume any values: a high taper would increase the axial thrust component, favoring the process described above, but would weaken the rolling edge excessively. On the contrary, a low taper value would allow to have a very resistant rolling edge, but would reduce the axial thrust component, nullifying the desired beneficial effects. Given this “trade-off”, it is necessary to select suitable ranges for the main geometric quantities of the rolling edge. The set goal is to reduce, without excessively weakening the rolling edge, the increase in the DK diameter of the radially internal ring 34 by percentages between 25% and 35% depending on the applications.

After carrying out an extensive experimental campaign in order to verify the above considerations, the writer has found that the best results to optimize the deformation of the radially inner ring and the force to be applied to the tool for the orbital deformation processing are obtained by selecting appropriate values of two parameters.

A first parameter k is defined as the ratio between the taper α of the surface 27 expressed in degrees and the radial thickness s of the cylindrical portion 26 'of the rolling edge expressed in millimeters:

k = α / s

in particular, the parameter k can assume values between 0.03 mm <-1> and 2 mm <-1>. Considering that a standard thickness value for a rolling edge is 5 mm and that the thickness variation range is between 3 mm and 7 mm, a value beyond which the orbital deformation process would be very difficult, it results that the taper value will be included in a range between 0.2 ° and 6 °. Compliance with this parameter is essential to prevent the rolling edge 25 from weakening too much in the lower radial thickness end section.

Advantageously, a second parameter h is defined as the ratio between the conicity of the surface 27 expressed in degrees and the length L 'of the rolling edge 25, or the depth of the hole 26, expressed in millimeters

h = α / L '

in particular, the parameter h can assume values between 0.125 mm <-1> and 0.5 mm <-1>. Considering that a standard value of the length L 'is equal to 11 mm and that the range of variation of the length L' can be between 8 mm and 16 mm, it follows that the taper value will be between 2 ° and 4 °. Compliance with this second parameter h allows to achieve a further advantage, namely to ensure that the rolling edge 25 has a minimum length of the cylindrical portion 26 '.

The length L of the conical surface 27 of the axially internal portion 28 is also related to the thickness s of the rolling edge 25 and its length L '. Considering that, as already mentioned, the range of variation of the length L 'is between 8 mm and 16 mm, the length L of the conical surface 27 can be between 5 mm and 8 mm. Advantageously, better results are obtained if the value of this length L is between 6 mm and 7 mm.

Finally, the connection radius R between the conical surface 27 and the axially internal flat surface 29 of the rolling edge 25 must assume a value between 0.5 mm and 2.5 mm. Advantageously, better results are obtained if the value of this rounding radius R is almost equal to 1.5 mm.

An example of sizing of the rolling edge is as follows: thickness s equal to 5 mm, length L 'of the rolling edge equal to 11 mm, taper α equal to approximately 3 °, length L of the conical surface 27 of the axially internal portion 28 equal to approximately 6.5 mm and the radius R equal to 1.5 mm.

The purposes of the present invention are preferably achieved by also optimizing the tool to be used for the orbital deformation.

With reference to figures 5 and 6, where figure 6 is the detail Z on an enlarged scale of figure 5, the orbital deformation processing is carried out by means of a tool schematized in figure 5 and indicated as a whole with 50, which has a cylindrical body 51, an annular press portion 52, with a pressing surface 53, also annular. In the detail of figure 6 it is easy to identify the opening angle β�� between the pressing surface 53 and a flat surface 54 radially internal with respect to the pressing surface 53. The value of the opening angle β has been optimized with respect to those normally used according to the known art.

The modified profile of the orbital deformation tool acts above all in the initial deformation phase in order to increase the compression phase and reduce the radial expansion of the diameter DK of the radially inner ring 34, in turn induced by the radial deformation which tool causes on the rolling edge 25 of the flanged inner ring 20. The experimental campaign mentioned above has led to the optimization in this sense of the opening angle β of the tool which must be between 5 ° and 40 ° starting from the flat surface 54 of the tool.

The set of all dimensional optimizations, described above, changes gives greater deformability of the rolling edge 25 with all the advantages described below.

First of all, the reduction of the force necessary for the processing of orbital deformation in order to obtain the rolled edge 22. In this way it will not be necessary to use orbital deformation machines with superior performance even when a very high load is required, for example higher than 240 kN. Consequently, for the same application, energy consumption will also be reduced during the use of the orbital deformation machine.

On the contrary, with the same applied force, an increase in the retention force of the deformed material of the rolled edge on the radially inner ring 34 is obtained.

Furthermore, the increase in the DK diameter of the radially inner ring 34 is reduced from 25% to 35% depending on the applications. Consequently, the stress state of the radially inner ring is also reduced. This allows a better assembly of the seal and a reduction in the formation of cracks in the radially inner ring.

As for the tool, its geometry is more simplified with a consequent increase in tool life and cost reduction. In addition, wider tolerances will be possible for the initial contact part of the tool with the respective contact portion of the rolling edge, resulting in a further reduction in the cost of the tool.

In addition to the ways of implementing the invention, as described above, it should be understood that there are numerous further variants. It must also be understood that these methods of implementation are only examples and do not limit the object of the invention, nor its applications, nor its possible configurations. On the contrary, although the above description makes it possible for the skilled person to implement the present invention at least according to an exemplary configuration thereof, it must be understood that numerous variations of the components described are conceivable, without thereby departing from the object of the invention. invention, as defined in the appended claims, interpreted literally and / or according to their legal equivalents.

Claims (9)

CLAIMS 1. Flanged inner ring (20) of a rolling bearing belonging to a motor vehicle wheel hub assembly, said flanged inner ring (20) comprising in its axially inner end a rolling edge (25) configured to axially preload a radially inner ring (34) after being plastically deformed by means of orbital deformation, wherein said rolling edge (25) comprises a conical surface (27) of an axially internal portion (28) of the rolling edge (25) itself and characterized in that a first parameter (k) defined as the ratio between the taper (α) of the conical surface (27), expressed in degrees, and the thickness (s) of the rolling edge (25), expressed in millimeters, takes values between 0 , 03 mm <-1> and 2 mm <-1>. Flanged inner ring (20) according to claim 1, wherein the taper (α) � of the conical surface (27) is between 0.2 ° and 6 °. 3. Flanged inner ring (20) according to claim 1, where a second parameter (h) defined as the ratio between the taper α of the surface (27), expressed in degrees, and the length (L ') of the edge of rolling (25), expressed in millimeters, assumes values between 0.125 mm <-1> and 0.5 mm <-1>. 4. Flanged inner ring (20) according to claim 3, wherein said taper (α) is comprised between 2 ° and 4 °. Flanged inner ring (20) according to one of claims 1 to 4, wherein the length (L) of the conical surface (27) of the distal portion (28) is between 5 mm and 8 mm. 6. Flanged inner ring (20) according to claim 5, wherein the length (L) is between 6 mm and 7 mm. Flanged inner ring (20) according to one of claims 1 to 6, wherein a radius (R) between the conical surface (27) and an axially inner flat surface (29) of the rolling edge (25) has a length between 0.5 mm and 2.5 mm. 8. Flanged inner ring (20) according to claim 7, wherein the length of the connecting radius (R) is approximately equal to 1.5 mm. 9. A wheel hub assembly (10) for motor vehicles, comprising an internal flanged ring (20) provided with a radially internal raceway (20 ') and a bearing unit (30) in turn comprising: - a radially external ring (31) provided with respective radially external rolling raceways (31 '), - a radially inner ring (34) provided with a radially inner raceway (34 '), - a plurality of rolling bodies (32, 33) positioned between the corresponding inner and outer raceways, the wheel hub assembly (10) being characterized by the fact that the internal flanged ring (20) is made according to one of the preceding claims.