TECHNICAL FIELD OF THE INVENTION

This invention relates to a rolling bearing assembly comprising, amongst others, a target fast in rotation with the outer ring of a rolling bearing and adapted to cooperate with a sensor unit, in order to determine a rotation parameter of the rolling bearing assembly. The invention also relates to methods for mounting such a rolling bearing assembly onto a member having a shaft and a hub.

BACKGROUND OF THE INVENTION

A rolling bearing comprises an inner ring, an outer ring and several rolling bodies installed between these two rings. These rolling bodies can be balls, rollers or needles. In the sense of the present invention, a rolling bearing can be, for instance, a ball bearing, a roller bearing or a needle bearing.

It is known to use a tachometer in order to determine the rotation speed of a member supported by a rolling bearing. As considered in EP-A-1 251 354, one can use a sensor assembly including an active part, such as a magnetic multipolar ring, forming a target whose rotation is detected by a sensor. This active part is mounted on a synthetic support member fast in rotation with the outer ring of a ball bearing, whereas the sensor is mounted on a body fast in rotation with the inner ring of the bearing. Such a device is globally satisfactory. However, in case the diameter of the ball bearing is small, in particular inferior to 30 mm, the size of the active part or target is reduced to the extent that the number of magnetic poles of the target must be decreased. Under such circumstances, the precision of the detection obtained with the sensor and the active part is not always satisfactory.

SUMMARY OF THE INVENTION

This invention aims at solving the above-mentioned problem with a new rolling bearing assembly which allows to accurately determine a rotation parameter of a rolling bearing, even in case the rolling bearing has a small diameter.

To this end, the invention concerns a rolling bearing assembly comprising a rolling bearing having an inner ring and an outer ring, a target adapted to rotate with the outer ring around the rotation axis of the rolling bearing, and a sensor unit including at least one sensing element adapted to read the target. According to the invention, the internal diameter of the target is larger than the outer diameter of the outer ring of the rolling bearing.

Thanks to the invention, the target, which is sometimes known as the "encoder washer" can be large enough to allow a precise detection of its rotation by the sensor unit, even if the diameter of the rolling bearing is small. In particular, the number of magnetic poles of the target can be larger than the corresponding number of poles for rolling bearing assemblies of the prior art.

In the present description, the words "axial", "radial", "axially", "radially", "centrifugal", "centripetal" and similar words relate to the axis of rotation of the outer ring of the bearing with respect to the inner ring. A direction is "axial" when it is parallel to this axis and "radial" when it is perpendicular and secant with this axis. For instance, a radial thickness is measured radially with respect to the axis of rotation.

According to further aspects of the invention, which are advantageous but not compulsory, the rolling bearing assembly might incorporate one or several of the following features:

- The target is mounted on a radial inner face of a flange. This flange supports and mechanically protects the target. This flange is advantageously metallic.

- The sensing element is located radially inside the target and inside the flange.

- The flange is fast in rotation with the outer ring of the rolling bearing. In such a case, the outer ring advantageously has a peripheral outer groove adapted to receive a part of the flange for wedging the flange on the outer ring.

- The rolling bearing is adapted to be wedged into a first housing of a member and the flange is adapted to be wedged into a second housing of the same member, for mechanical connection between the flange and the outer ring.

- A sealing gasket is fixedly mounted on the sensor unit and is in sliding contact with the radial inner face of the flange.

- The sensor unit comprises a holding part for holding the sensor element, a securing part of securing the sensor unit to the inner ring and a resilient part attached to the holding part and to the securing part, the elasticity of the resilient part allowing a displacement of the holding part relative to the securing part, this displacement having a component parallel to the axis of rotation of the rolling bearing.

- The body of the sensor unit is in abutment against the inner ring of the rolling bearing and adapted to transmit an axial force to this inner ring.

The invention also relates to several methods for mounting a rolling bearing assembly as mentioned here-above having its target mounted on a radial inner face of a flange, this rolling bearing assembly being mounted onto a support member. The first method comprises the steps of:

a) fastening the flange on the outer ring of the rolling bearing;

b) pushing the rolling bearing into a respective housing of the hub, with an effort parallel to the rotation axis of the rolling bearing, exerted on a lateral face of the inner ring and/or the outer ring;

c) installing the sensor unit around the shaft with the sensing element in axial alignment with the target.

The second method of the invention comprises the steps of:

e) pushing the rolling bearing into a first housing of the hub, with an effort parallel to its rotation axis, exerted on a lateral face of the inner ring and/or of the outer ring;

f) installing the flange into a second housing of the hub;

g) installing the sensor unit around the shaft, with the sensing element in axial alignment with the target.

In case the rolling bearing assembly has a sealing gasket as mentioned here-above, the gasket is brought into sliding contact with the radial inner face of the flange during step c) or step g).

The third method the invention comprises the following steps:

I) fastening the flange with the outer ring on the rolling bearing;

m) fastening a body of the sensor unit with the inner ring of the rolling bearing, the sensing element being in axial alignment with a target;

n) pushing the rolling bearing equipped with the flange and the sensor unit into a housing of the hub, with an effort parallel to the axis of rotation of the rolling bearing.

The fourth method of the invention comprises the following steps:

r) pre-assembling the rolling bearing assembly by fastening a body of the sensor unit to the inner ring of the ball bearing and mounting the flange around the sensor unit body;

s) pushing the rolling bearing assembly in respective housings of the hub, with an effort parallel to the rotation axis of the rolling bearing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood on the basis of the following description which is given in correspondence with the annexed figures and as an illustrative example, without restricting the object of the invention. In the annexed figures: figure 1 is a perspective view of a hub and a fork of a two-wheeled vehicle, the hub including a rolling bearing assembly according to the invention;

figure 2 is a partial cross-section, at a larger scale and along plane II on figure 1 , showing a rolling bearing assembly used in the device of figure 1 ;

- figure 3 is an enlarged view of detail III on figure 2;

figure 4 is a detailed view similar to figure 3 for a rolling bearing assembly according to a second embodiment of the invention;

figure 5 is a detailed view similar to figure 3 for a rolling bearing assembly according to a third embodiment of the invention and

- figure 6 is a detailed view similar to figure 3 for a rolling bearing assembly according to a fourth embodiment of the invention.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

Figure 1 depicts the use of a rolling bearing assembly 2 in conjunction with a shaft 4 and a hub 6. The hub 6 belongs to a non-represented wheel which is held by two fork members 8 supporting shaft 4. The rolling bearing assembly 2 of the invention is used in conjunction with another rolling bearing assembly 3 in order to support, with a possibility of rotation, hub 6 around shaft 4 which is stationary when fork members 8 are stationary.

Rolling bearing assembly 2 includes a ball bearing 10 comprising an inner ring 102 and an outer ring 104 defining between them a rolling chamber where balls 106 are held in position by a cage 108. Ring 102 is fast with shaft 4 and ring 104 is rotatable around a central axis X ₁₀ of rolling bearing 10 which is superimposed with the central longitudinal axis X ₄ of shaft 4 when rolling bearing 10 is mounted on shaft 4.

Rolling bearing assembly 2 also includes means to determine a rotation parameter of the outer ring 1 04 , with respect to the in ner ring 102. A rotation parameter is representative of the pivoting movement of one part with respect to another. Such a parameter can be an angle measuring the angular position of one part with respect to the other, around the central axis X ₁₀ of ball bearing 10. Such a parameter can also be a speed, a displacement, an acceleration or a vibration.

These detection means include a sensor unit 20 having a body 202 supporting a Hall effect cell 204 forming a sensing element. An electric cable 205 connects cell 204 to an appropriate electronic control unit which is remote from rolling bearing assembly 2. Alternatively, some electronic components can be embedded in body 202 in order to treat the output signal of cell 204.

Body 202 is mounted on an annular shoe or spacer 203 which also belongs to sensor unit 20. Shoe 203 is fitted around shaft 4 and wedged onto inner ring 102 thanks to a skirt 2032 blocked in an inner peripheral groove or recess 1022 of inner ring 102. Thus, body 202 is fast in rotation with inner ring 102. A terminal nut 40 is mounted on shaft 4 and adapted to exert on shoe 203 an axial effort E ₄₀ , that is an effort parallel to axis Xi ₀ . This axial effort is transmitted, as an effort E ₃₀ , by shoe 203 to inner ring 102 which is in abutment against a spacer 42 extending between rolling bearing assemblies 2 and 3.

A metallic flange 50 is wedged on outer ring 104. Flange 50 acts as a cover for an encoder washer 60 which constitutes a target for Hall effect cell 204. Encoder washer 60 is magnetically active and includes several magnetic North and South poles regularly distributed around axis Xi ₀ in working configuration of rolling assembly 2. Encoder washer 60 is mounted on the radial inner face 502 of flange 50. Encoder washer 60 can be glued onto face 502 or blocked against this surface by an elastic deformation of flange 50.

Sensing element 204 is arranged to detect encoder washer 60 in a radial direction.

Flange 50 includes a first cylindrical portion 504 having a circular cross-section and defining face 502. Flange 50 also includes a second cylindrical portion 506 with a circular cross-section, these two portions being joined together by an annular portion 508 which is perpendicular to axis X ₁₀ . Thanks to annular portion 508, cylindrical portions 504 and 506 can have different inner diameters.

Portion 506 is wedged onto outer ring 104. More precisely, portion 506 is introduced within an outer groove or recess 1042 of outer ring 104, so that items 50 and 104 are fast in rotation with each other.

Other possibilities to fasten flange 50 onto outer ring 104 include gluing, force fitting and screwing.

D ₁₀₄ denotes the outer diameter of outer ring 104, that is the maximum diameter of ball bearing 10. The smaller this diameter, the more compact ball bearing 10 is and the more compact rolling bearing assembly 2 can be.

d ₆ o denotes the internal diameter of encoder washer 60, that is the dimension of the target which determines the geometry of a radial air gap G formed between cell 204 and the radial inner face 602 of encoder washer 60. Diameter d ₆ o is actually the diameter of face 602.

According to the invention, diameter d ₆ o is larger than diameter D ₁₀₄ . This allows encoder washer 60 to be large enough to define several well differentiated magnetic poles, even if diameter D ₁₀₄ is small, e.g. inferior to 30 mm.

This configuration is obtained thanks to the use of flange 50 which constitutes a connection part between elements 60 and 104, with an increase of diameter between its part 506 connected to outer ring 104, and its part 504, connected to encoder washer 60. Flange 50 also works as a radial cover which shields encoder washer 60 against chocks and/or pollution. In other words, encoder washer 60 is protected by flange 50 since it is located radially inside cylindrical portion 504.

d ₅₀ 4 denotes the internal diameter of portion 504 and e ₆ o denotes the radial thickness of encoder washer 60. Diameter d ₅₀ equals diameter d ₆ o plus twice thickness e ₆ o-

A sealing gasket 70 is mounted on body 202 and extends radially outwardly from this body so that its terminal deformable lip 72 comes in sliding contact against radial inner face 502 of flange 50. Thus, air gap G and encoder washer 60 are efficiently protected against pollution, in particular water or humidity.

Mounting of rolling bearing assembly 2 onto shaft 4 and hub 6 occurs as follows: first, one mounts encoder washer 60 within flange 50, so that these two elements are fast in rotation with each other. Then flange 50 is fastened around outer ring 104 by introducing its portion 506 within outer groove 1042. This can occur before or after ball bearing 10 is assembled.

Ball bearing 10 equipped with flange 50 and encoder washer 60 is then pushed into a housing 62 defined within hub 6 around shaft 4. This is obtained by exerting an axial effort E-i on a lateral face 1024 of inner ring 102 and/or a lateral face 1044 of outer ring 104 which remain accessible when ball bearing 10 is being introduced within housing 62.

It is then possible to install sensor unit 20 and shoe 30 around shaft 4 and to push them towards ball bearing 10 so that cell 204 is axially aligned with encoder washer 60. This corresponds to the introduction of skirt 302 in groove 1022 and brings sealing lip 72 in sliding contact with face 502 of flange 50.

It is then possible to screw nut 40 on shaft 4 in order to immobilize rolling bearing assembly 2 with respect to shaft 4, spacer 42 and hub 6, thanks to efforts E ₄₀ and E ₃₀ .

In the second, third and fourth embodiments of the invention represented on figures

4 to 6, the elements similar to the ones of the first embodiment have the same references. The second, third and fourth embodiments work generally in the same way as the first em bod iment and one descri bes hereafter mai n ly the differences between these embodiments.

In the second embodiment of a rolling bearing assembly 2 represented on figure 4, a ball bearing 10 having an inner ring 102 and another ring 104 is located in a first housing 62 of the hub 6. The encoder washer 60 is mounted on the radial inner face 502 of a metallic cylindrical sleeve 50 which forms a flange and is received in a second housing 64 of hub 6. In other words, outer ring 104 and flange 50 are not directly connected to each other. Instead, they are fast in rotation with each other, once assembly 2 is mounted on hub 6 and shaft 4, thanks to the fact that they are both immobilized within respective housings 62 and 64 of hub 6.

As in the first embodiment, the internal diameter d ₆ o of encoder washer 60 which forms a target is larger than the outer diameter D ₁₀₄ of outer ring 104. This enables encoder washer 60 to be large enough for a precise detection by Hall effect cell 204.

Rolling bearing assembly 2 of this embodiment is mounted with respect to shaft 4 and hub 6 in the following way: First, ball bearing 10 is pushed into the first housing 62, thanks to an axial effort E-i parallel to the central axis Xi ₀ of ball bearing 10. Then, flange 10 already equipped with encoder washer 60 is installed within the second housing 64 and immobilized therein by cooperation of shapes or gluing.

After that, sensor unit 20, which is mounted on a shoe 203 as in the first embodiment, is pushed against ball bearing 10 so that its cell 204 is axially aligned with encoder washer 60 and the sealing lip 72 of the sealing gasket 70 comes into sliding contact with respect to the inner radial face 502 of sleeve 50.

In the third embodiment of the invention represented on figure 5, rolling bearing 10 is mounted within a housing 62 of the hub 6 and a flange 50 has two cylindrical portions 504 and 506 connected by an annular portion 508, the cylindrical portion 506 with the smallest diameter being wedged into an outer groove 1042 of the outer ring 104 of ball bearing 10 as in the first embodiment. A difference with respect to the first embodiment is that the radial dimension of annular portion 508 is larger, so that the difference between the inner diameter d ₆ o of the encoder washer 60 mounted on the radial inner face 502 of flange 60, on the one hand, and the outer diameter D ₁₀₄ of outer ring 104, on the other hand, is larger than in the first embodiment. Inner diameter d ₆ o is larger than outer diameter D ₁₀₄ .

Another difference lies in the fact that the body 202 of sensor unit 20 includes a holding part 206 for holding the Hall effect cell 204, a securing part 207 for securing unit 20 to the inner ring thanks to a skirt 208 wedged into an inner groove 1022 of ring 102 as skirt 302 in the first embodiment, and a resilient part 209 is attached to parts 206 and 207. Resilient part 209 is elastically deformable in a direction D parallel to axis X ₁₀ in the working configuration of rolling bearing assembly 2. Thus, the elasticity of part 209 allows a displacement, parallel to direction D and axis Xi ₀ , of holding part 206 relative to securing part 207.

A sealing gasket 70 is fastened to radial inner face 502 and extends radially towards a radial outer surface 2062 of holding part 206 against which it comes into sliding contact.

The elasticity of resilient part 209 allows to pre-assemble ball bearing 10, flange 50 equipped with encoder washer 60 and sensor unit 20 and to push the rolling bearing equipped with the flange and the sensor into housing 62 thanks to an axial effort E ₂ exerted on holding part 206 and/or on securing part 207. This effort E ₂ can be transmitted to ball bearing 10 thanks to the elastic deformation of resilient part 209.

In the fourth embodiment of the invention represented on figure 6, a flange 50 in the form of annular cup is used to surround and hold an encoder washer 60 forming a target for a Hall effect cell 204 of a sensor unit 20, as in the second embodiment. This flange is not directly connected to the outer ring 104 of the ball bearing 10. The ball bearing 10 is received within a housing 62 of hub 6 whereas the flange 50 is received within a housing 64 of hub 6. The shape of flange 50 is different from the second embodiment insofar as it has a L cross-section with an annular part 509, opposite to ball bearing 10 and extending radially towards the central axis Xi ₀ of ball bearing 10 and supporting a sealing gasket 70 whose sealing lip 72 is in sliding contact with an external surface 322 of a ring 32 mounted around the body 202 of sensing unit 20. Body 202 is held in position around shaft 4 thanks to an annular shoe 203, as in the first embodiment.

The inner diameter d ₆ o of encoder washer 60 is larger than the outer diameter D ₁₀₄ of the outer ring 104 of the ball bearing, as in the other embodiments.

Such a structure enables to preassemble sub-assembly 2 prior to its mounting onto shaft 4 and hub 6. Items 50, 60 and 70 are held in position around sensing unit 20 because of the shape of flange 50. Thus, sub-assembly 2 can be manipulated as a single mechanical unit prior to its installation onto shaft 4 and hub 6. Ball bearing 10 can be pushed into housing 62 by applying an effort E-i parallel to its rotation axis X ₁₀ , exerted on a lateral face of the inner ring 102 and/or of the outer ring 104, whereas flange 50 can be pushed into housing by an axial effort E ₃ on its annular part 509.

In all embodiments, the Hall effect cell 204 is located radially inside the encoder washer 60 and the flange 50, so that the flange protects both the encoder washer 60 and the cell 204.

According to non represented alternative embodiments of the invention, sensor unit 20 may include more than one Hall effect cell 204.

The features of the embodiments mentioned here-above can be combined.

As mentioned here-above, the invention is particularly adapted for realizing a tachometer of a two-wheeled vehicle. However, other applications can be considered.