TECHNICAL FIELD OF THE INVENTION This invention relates to a rolling bearing assembly comprising, amongst others, an encoder washer fast in rotation with one ring of a rolling bearing and a sensor adapted to determine a rotation parameter of the encoder washer. The invention also relates to an electric motor equipped with such a rolling bearing assembly.

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 bearings can be balls, rollers or needles. In the meaning of the present invention, a rolling bearing can be, for instance, a ball bearing, a roller bearing or a needle bearing.

In the field of rolling bearings, it is known to use a tachometer in order to determine the rotation speed of a member supported by a rolling bearing. In such a case, a sensor is generally mounted on a support member which has to be immobilized with respect to one of the rings of the rolling bearings, the so-called fixed ring. Mounting of the support member with respect to the fixed ring induces that the axial volume of a rolling bearing assembly with a tachometer is relatively high. Moreover, the electronic components necessary to make the sensor work properly must be installed in its vicinity, which generally increases the overall volume of the rolling bearing assembly.

SUMMARY OF THE INVENTION

This invention aims at solving these problems with a new rolling bearing assembly which provides a better axial compactness, together with a possibility to locate some electronic control components associated with a sensor in its vicinity. To this end, the invention concerns a rolling bearing assembly comprising:

- a rolling bearing with an inner ring, an outer ring and rolling bodies between the inner and outer rings, - a flange with a housing where the rolling bearing is at least partially received,

- an encoder washer fast in rotation with the inner ring, and

- at least one sensor adapted to detect a rotation parameter of the encoder washer with respect to the flange, wherein an annular body radially surrounds the outer ring of the rolling bearing in the housing and forms a support member for the sensor in a position where the sensor can detect the rotation parameter of the encoder washer.

Thanks to the invention, the annular body fulfills a double function, namely positioning of the ball bearing within the housing of the flange and supporting the sensor in a working position. In other words, a correct position of the sensor can be obtained, thanks to the tubular body, without adding a dedicated element to the assembly in order to support this sensor. No dedicated immobilization means of such an element on a fixed part of the assembly must be provided, which improves the axial compactness of the assembly. The annular body of the invention also improves the serviceability of the rolling bearing assembly, insofar as the sensor and its associated electronic components can be easily accessed.

In the present description, the words "axial", "radial", "axially" and "radially" relate to the axis of rotation of the rings of the rolling bearing one with respect to the other. A direction is "axial" when it is parallel to this axis and "radial" when it is perpendicular and secant with this axis.

A rotation parameter of one part with respect to the other is a parameter which is representative of a pivoting movement of one part with respect to the other. Such a parameter can be an angle measuring the angular position of one part with respect to the other, around the central axis of the rolling bearing. Such a parameter can also be a speed, a displacement, an acceleration or a vibration.

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 taken in any technically admissible configuration: - The annular body is made of one annular skirt and one support member integral with the annular skirt, the annular skirt radially surrounding the outer ring of the ball bearing and being received in the housing of the flange, whereas the support member extends outside of the housing. - The support member comprises an annular flat part, contiguous to the annular skirt and perpendicular to the axis of rotation of the inner and outer rings, a first collar and a second collar extending, from the flat part, opposite to the annular skirt. In such a case, the first and second collars extend advantageously respectively along the radial inner and outer edges of the flat part. The sensor is advantageously mounted on the first collar.

- The support member holds at least one printed circuit board (PCB), in particular a PCB connected to the sensor. A housing for the printed circuit board is advantageously defined between the first and second collars of the annular body. - The printed circuit board is flat and perpendicular to the axis of rotation of the inner and outer rings of the rolling bearing.

- The printed circuit board is annular and extends over 360°around the axis of rotation. Alternatively, the printed circuit board can extend on a limited angular sector with respect to the axis of rotation. - The annular body is made of a resilient material, preferably of a molded synthetic material.

- A cap is removably mounted on the support member, in a position where it covers at least the annular body, the sensor and the encoder washer. This cap is advantageously held in position on the flange by screws which go through corresponding holes of the annular body.

The invention also concerns an electric motor equipped with a rolling bearing assembly as mentioned here-above. The overall axial dimension of such an electric motor can be reduced with respect to existing motors provided with a tachometer. According to an advantageous aspect of the invention, the annular body of the rolling bearing assembly also forms a support member for at least some of the electronic control components of the motor. This further improves the compactness of the electric motor. 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 schematic partial axial cut view of an electric motor according to the invention provided with a rolling bearing assembly according to the invention;

- Figure 2 is an enlarged view of detail Il on figure 1 ; - Figure 3 is a perspective view, partially cut away, of the rolling bearing assembly represented on figures 1 and 2; and

- Figure 4 is a perspective view, at a larger scale, of an annular body belonging to the rolling bearing assembly of figure 3.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

A motor 2 partly represented on figure 1 comprises a stator 4 and a rotor 6 provided with non-represented magnetically cooperating elements, in order to drive the rotor 6 in rotation around an axis X-X'.

Rotor 6 is mounted on and fixed in rotation with a shaft 8 centered on axis X-X'. Stator 4 is held in position around rotor 6 by a non-represented frame.

A flange 10 closes the overall housing of motor 2 and is provided with a central opening 12 for the passage of the shaft 8. A ball bearing 20 is mounted on flange 10 and supports shaft 8 with a possibility of rotation around axis X-X'. Ball bearing 20 comprises an inner ring 22, an outer ring 24, several balls 26 and a cage 28 holding the balls in position between rings 22 and 24.

An encoder washer 30 is fixedly mounted on inner ring 22. This washer 30 comprises a metallic armature 32 having an inner radial collar 322 snapped within an annular groove 222 of ring 22. Encoder washer 30 also includes an active part 34 which is magnetized and defines, along its circumference, an alternation of North poles and South poles, respectively formed by permanent magnets. Alternatively to a magnetized washer, encoder washer 30 can include an active part made of a magnetic metal and provided with notches or holes. According to alternative embodiments, detection of the rotation of washer 30 can be performed by an inductive or optical sensor.

Outer ring 24 is received in a central recess 14 of flange 10 which is centered on axis X-X'. In other words, recess 14 is a housing accommodating the radial external portion of ball bearing 20.

An annular body 40 is mounted around outer ring 24. An annular body 40 is made of a molded synthetic material, for instance a polymeric material such as PA66 or PEAK or a composite material comprising reinforcing fibers such as glass fibers. This annular body is resilient. Alternatively, annular body 40 can be made of metal, while being also resilient.

Annular body 40 comprises an annular skirt 42 which is introduced within housing 14, between the outer radial surface 242 of outer ring 24 and the peripheral surface 142 of housing 14. In other words, annular skirt 42 surrounds ball bearing 20 within housing 14 and this part of annular body 40 guarantees that the ball bearing 20 is radially correctly positioned with respect to the flange 10. Moreover, as it is resilient, skirt 42 can absorb vibrations due to a potential unbalance of rotor 6 and/or shaft 8. Annular skirt 42 can also absorb differential dilatations between flange 10 and ball bearing 20. Annular body 40 also has an annular flat part 44 which is perpendicular to skirt 42 and extends substantially perpendicularly to axis X-X' in the configuration of figure 1.

At the level of the respective inner edge 442 and outer edge 444 of part 44, two collars 46 and 48 extend with respect to part 44, in a direction opposite to skirt 42. An annular volume V ₄₀ having a substantially U shaped cross section is defined by annular part 44, inner collar 46 and outer collar 48. Annular part 44 forms the base or bottom of the U section of volume V ₄₀ .

Annular part 44 is provided with four holes 446 evenly distributed around a central axis X ₄ O of annular body 40 which is superimposed with axis X-X' in the mounted configuration of the ball bearing assembly. U shaped guiding means 448 extend from the inner surface of collar 48 and define a channel for guiding the stem of a screw towards each respective hole 446. Annular body 40 also has a second annular flat part 49 which is parallel to part 44. Part 49 extends radially toward axis X40 from the edge of inner collar 46 opposite to annular part 44.

Annular body is made of one piece: parts 42 to 49 are integral with each other.

A magnetic sensor or sensing element 50, e.g. provided with a Hall effect cell, is fixedly mounted on the inner radial face 462 of inner collar 46. Sensor 50 can be glued or otherwise fixed on annular body 40 and parts 44 to 49 form together a support member for sensor 50, this support member being held in position with respect to flange 10 by the cooperation of housing 14, ball bearing 20 and skirt 42.

This sensor 50 is connected by an electrical cable 52 to a printed circuit board 60 or "PCB" installed within volume V ₄₀ . This PCB 60 is flat and in the form of an annulus perpendicular to axis X-X'. A passage 464 is provided through inner collar 46 for cable 52. PCB 60 is connected by non represented means to a voltage supply and an electronic control unit adapted to process an electronic signal produced by PCB 60 and representative of the rotation of washer 30, as measured by sensor 50.

A metallic cap or cover 70 is used to protect parts 30 to 60 and has a main flat portion 72, an inner edge portion 74 and an outer edge portion 76 adapted to surround radially, respectively inwardly and outwardly, parts 30 and 40.

Flat portion 72 is also provided with four holes 726 which are supposed to be aligned with the four holes 446 of annular body 40 so that four screws 80 can be inserted simultaneously within holes 446 and 726 and within threaded holes 16 provided in flange 10.

Screws 80 firmly and reversibly immobilize annular body 40 and cap 70 with respect to flange 10. The axial position of annular body 40 with respect to flange 10 is used to immobilize ring 24 within housing 14.

Therefore, annular body 40 is efficient to immobilize ball bearing 20 with respect to flange 10 both axially and radially with respect to axis X-X' thanks to parts 42 and 44. On the other hand, parts 44 to 49 form a support member or section of body 40 which is integral with annular skirt 42 and extends outside housing 14 in such a way that it holds sensor 50 and PCB 60 in a position where they can fulfill their respective functions.

In other words, a single part, namely annular body 40, is used to hold the ball bearing 20 in position with respect to the flange 10 and the sensor 50 in position with respect to the encoder washer 30. This induces that the rolling bearing assembly formed by items 10, 20, 30, 40, 50, 60, 70 and 80 is compact, in particular along an axial direction, as compared to existing assemblies.

Because of the geometry of annular body 40, PCB 60 can be installed "radially", that is in a plane which is perpendicular to axis X-X', so that it can have a relatively large surface, without having a negative influence on the axial compactness of rolling bearing assembly 10-80 and of motor 2.

For the clarity of the figures, the electronic components mounted on PCB 60 are not represented. As shown on the figures, PCB 60 is annular and extends over

360°around axis X-X'. This is not compulsory and P CB 60 can extend on a limited angular sector around axis X-X', e.g. 90° or even l ess. This is advantageous insofar as the axial dimensions of the stator 4 vary around axis X-X', so that rolling bearing assembly 10-80 can be integrated into motor 2 in a configuration such that

PCB 60 is located in front of a part of stator 4 which is relatively short along axis X-

X'. This allows to mount rolling bearing assembly 10-80 very close to stator 4, without interference between these items.

Since PCB can be relatively large because of the size of volume V ₄₀ , it can also support electronic components used to control motor 2 and which are not functionally connected to sensor 50. In other words, a sort of an electronic control unit (ECU) can be located within ball bearing assembly 10-80 to control sensor 50 and other electronic parts of motor 2, without substantially increasing its volume, in particular its axial volume. Other ECUs of motor 2 can be reduced or even suppressed.

The invention also provides easy access to PCB 60 insofar as, as soon as screws 80, or any other reversible attachment means such as staples or fingers, and cover 70 have been removed, one can work on PCB 60 without having to further disassemble the rolling assembly. In particular, work can be done on PCB

60 without moving sensor 50 with respect to encoder washer 30 and without removing rolling bearing 20 from its housing 14. Therefore, serviceability of the ball bearing assembly 10-80 of the invention is improved.

The invention is represented on the figures in the case where housing 14 is accessible from the inside side of flange 10, that is from its side oriented towards the inside volume of motor 2, in particular towards stator 4 and rotor 6. This implies that screws 80 are only accessible once flange 10 has been separated from the frame of motor 2. However, according to a non-represented alternative embodiment, housing 14 can be accessible from outside flange 10. In such a case, items 20 to 80 are accessible from outside motor 2 without disassembling flange 10 from the frame of the motor.

The invention has been described in the case when one sensor 50 is used.

Alternatively, several sensors can be used, these sensors being held in position by annular body 40. The invention is applicable irrespective of the actual geometry of the flange 10. The number of screws used to hold annular body 40 in position with respect to flange 10 can be different from four.

The invention is particularly interesting for electric motors. However, it can also be used for other mechanical or electromachanical devices like gearboxes. Any kind of rolling bearing can be used with the invention.