SUPPORTING SYSTEM The invention concerns a shaft supporting system for an electric motor and an electric motor equipped with such a shaft supporting system. The invention also concerns a process for assembling the shaft supporting system.

In the field of electric motors, it is known to equip an electric motor with a shaft supporting system. This shaft supporting system is an instrumented bearing assembly that fulfills a plurality of sensing functions in addition to the normal bearing operation. Indeed, this instrumented bearing assembly is able to provide the relative position of the inner ring in relation to the outer ring, the rotational speed, the direction of rotation and the magnitude of acceleration or deceleration.

WO- A-2013/050801 discloses an instrumented bearing assembly comprising a bearing that is formed by a rotating inner ring and a fixed outer ring. An impulse ring is secured to the inner ring. More precisely, the impulse ring is mounted on an annular support that is squeezed between the shaft of the rotating machine and the inner ring internal surface. To that end, inner ring delimits a notch receiving an end portion of the annular support. A sensor element radially faces the impulse ring. This sensor element is supported by a carrier that is secured to the outer ring. Indeed, the carrier includes an end portion that is clipped within a peripheral groove delimited on the outer surface of the outer ring. A peripheral groove is quite expansive to manufacture and manufacturing tolerances may lead to a concentricity deviation of the sensor element with respect to the impulse ring. As a result, the output delivered by the sensor element may be biased. The output may also be biased if the outer ring rotates as the sensor element is attached to it.

WO-A2009/004199 discloses a shaft supporting system for an electric motor comprising a carrier that includes a tubular portion. A radially outwardly extending flange and a radially inwardly extending portion extend from this tubular portion. The carrier supports a bearing and a sensor element for sensing the rotating motion of an impulse ring that is fixed to the inner ring. The impulse ring is overmolded with an annular support that is welded on the inner ring outer surface. The carrier includes radially protruding teeth that engage notches arranged in a body of the sensor element. Then, the bearing outer ring may rotate without involving a rotation of the sensor element. However, the bearing cannot be equipped with a sealing flange for retaining lubricant inside the rolling chamber of the bearing as the annular support is fixed to the inner ring outer surface. The invention intends to solve these problems by proposing a shaft supporting system with which the fixation of the impulse ring onto the inner ring does not disturb the mounting of a sealing flange and with which the sensor element is not connected to the bearing outer ring in a rotationally fixed manner.

To this end, the invention concerns a shaft supporting system for an electric motor, comprising a carrier that includes a tubular portion from which a flange extends radially outwardly with respect to a central axis of the shaft supporting system and a portion extends radially inwardly with respect to the central axis, this carrier supporting:

- a bearing including an inner ring dedicated to be mounted around a rotor shaft of the electric motor, an outer ring fitted to a first portion of a tubular portion inner surface and at least one row of rolling elements arranged between said rings, and

- a sensor element for sensing the rotating motion of an impulse ring fixed to the inner ring.

The carrier further comprises a collar extending axially from the radially inwardly extending portion in the direction of the bearing so as to define an annular volume with a second portion of the tubular portion inner surface, and the sensor element is received in the annular volume and radially faces the impulse ring.

Thanks to the invention, the carrier is shaped so as to define an annular volume for receiving the sensor element. The sensor element is then not connected to the bearing outer ring in a rotationally fixed manner. As a result, a rotation of the outer ring does not involve a rotation of the sensor element. In other words, the bearing function and the sensing function are separated. The impulse ring is attached to the outer ring so that it provides good concentricity between sensor element and impulse ring and better sensing performances. Moreover, the shaft supporting system is easy to manipulate and transport once assembled.

Further aspects of the invention which are advantageous but not compulsory are specified below:

- The radially outwardly extending flange and the radially inwardly extending portion extend from opposite ends of the tubular portion;

- The radially outwardly extending flange and the radially inwardly extending portion extend from a same end of the tubular portion;

- The radially inwardly extending portion extends at one end of the tubular portion and the radially outwardly extending flange extends from the middle of the tubular portion;

- The impulse ring is mounted on an annular support, comprising an axial portion fitted in a notch formed in the inner ring; - The annular support axial portion is designed to be fitted between an inner surface of the inner ring and the rotor shaft;

- The annular support comprises a radially outwardly extending shoulder;

- The sensor element comprises a casing holding a Hall effect cell mounted on an annular printed circuit board;

- An axial gap is defined between a free end of the collar and the bearing;

- The shaft supporting system includes wireless communication means for transferring the information measured by the sensor element;

- The sensor element includes an output cable;

- The output cable goes through the radially inwardly extending portion of the carrier;

- A radial gap between the impulse ring and sensor element is defined.

The invention also concerns a rotating machine, comprising a rotating shaft mounted coaxially within a housing and a shaft supporting system as previously defined, that is arranged coaxially between the rotating shaft and the housing.

The invention also relates to a process for assembling a shaft supporting system as previously defined, comprising steps consisting in

a) positioning the sensor element in the annular volume defined by the carrier, b) fixing the impulse ring to the inner ring,

c) positioning the bearing against sensor element, and in

d) axially stamping the tubular portion of the carrier in the direction of the bearing, so as to form a beading and to maintain axially the bearing and the sensor element between the beading and the collar.

The invention will now be explained in correspondence with the figures, and as an illustrative example, without restricting the object of the invention. In the figures:

- figure 1 is a sectional view representing a first embodiment of a shaft supporting system according to the invention, and

- figure 2 is a sectional view similar to figure 1 representing a second embodiment of a shaft supporting system according to the invention.

Figure 1 represents a shaft supporting system 2 for an electric motor. In practice, shaft supporting system 2 is dedicated to be arranged coaxially between a rotor and a stator of the motor. The rotor includes a shaft S1 that is represented in chain dotted line on figure 2 and that is supported by system 2. Shaft supporting system 2 is globally ring- shaped and centered on an axis X2. In practice, the axis of revolution of the rotor shaft S1 is superimposed with axis X2 when system 2 is in a working configuration. In the present document, the terms "axial" and "radial" must be interpreted with respect to axis X2. More precisely, an axial direction is parallel to axis X2 and a radial direction is perpendicular to axis X2.

In the present document, front direction represents a direction parallel to axis X2 and oriented to the left on figure 1 , while back direction represents a direction parallel to axis X2 and oriented to the right on the same figure.

Shaft supporting system 2 includes a carrier 4 that is centered on axis X2 and that includes a tubular portion 40 from which extends a radially outwardly extending flange 42 and a radially inwardly extending portion 44. Radially outwardly extending flange 42 extends approximately from the middle of the tubular portion 40, while radially inwardly extending portion 44 extends at the rear end of tubular portion 40. Carrier 4 is dedicated to be fixed within a bore B of the stator S2 of the electric motor, by means of radially outwardly extending flange 42. Stator S2 is also represented in chain dotted lines on figure 1 . Indeed, radially outwardly extending flange 42 includes through holes 042 for the passage of non-represented fixing screws. These fixing screws are screwed in complementary threaded holes delimited in an aluminum shield of the stator S2. Flange 42 then forms a means for fixing shaft supporting system 2 inside of the stator central bore B.

Carrier 4 supports a bearing 6 including an inner ring 60, dedicated to be mounted around the rotor shaft S1 in a rotationally fixed manner, and an outer ring 62 fitted to a front portion S40A of an inner radial surface S40 of the tubular portion 40. Ring 60 rotates then with the rotor shaft around axis X2 under operating conditions. Carrier 4 forms, on its inner surface S40, a beading 48 for axially positioning bearing 6. Beading 48 is obtained by a stamping process for example. This stamping process consists in inserting a non- represented puncher inside portion 40 in a direction parallel to axis X2 and oriented towards radially inwardly extending portion 44, so as to displace a portion of the material of the carrier 4 backwards. The puncher has an outer diameter that is superior to the inside diameter of carrier 4. The diameter difference between puncher and carrier 4 defines the radial distance at which beading 48 protrudes with respect to surface S40. The stamping process then consists in plastically deforming the carrier material. This operation can be performed at hot or cold temperature. Radially inwardly extending portion 44 supports the axial effort generated by the stamping process.

Bearing 6 further comprises one row of rolling elements 64 that are arranged between rings 60 and 62. In the illustrated example, rolling elements 64 are balls. Bearing 6 is mounted coaxially within carrier 4. The annular volume between rings 60 and 62 forms a rolling chamber that receives lubricant so as to ease the rolling contact between rolling elements 64 and the rolling surfaces of bearing rings. Lubricant is restrained within rolling chamber using two sealing flanges 66 and 68 that are respectively arranged at the front side and at the back side of bearing 6. Sealing flanges 66 and 68 prevent, on one hand, outside pollution from penetrating in the rolling chamber and, on the other hand, lubricant from escaping outside of the rolling chamber. Further, bearing 6 includes a cage 69 for maintaining balls 64 at equal intervals around axis X2.

Carrier 4 supports a sensor element 8 for sensing the rotating motion of an impulse ring 10 fixed to the rotating inner ring 60. To that end, carrier 4 comprises a tubular collar 46 extending axially from the radially inwardly extending portion 44 in the direction of bearing 6, that is in front direction, so as to define an annular volume V1 with a back portion S40B of inner radial surface S40. Sensor element 8 is received in annular volume V1 and radially faces the impulse ring 10. More precisely, collar 46 supports directly the sensor element 8, which means that sensor element 8 contacts the outer radial surface of collar 46. Sensor element 8 is arranged at the back of bearing 6. Sensor element 8 comprises a casing holding a non-represented Hall effect cell that is mounted on a nonrepresented annular printed circuit board. Sensor element 8 protrudes axially in front direction with respect to the free end 46a of collar 46. The protruding portion of sensor element 8 radially faces impulse ring 10. Further, sensor element 8 contacts outer ring 62 so that it is maintained axially between ring 62 and radially inwardly extending portion 44. Sensor element 8 is also maintained radially between portion 40 and collar 46.

An axial gap g1 is defined between the free end 46a of collar 46 and bearing 6. This axial gap g1 allows defining a free space for positioning impulse ring 10.

Impulse ring 10 is mounted on an axial portion 12c of an annular support 12. Annular support 12 is formed of a metal or plastic sheet centered on axis X2 and comprising another axial portion 12a fitted inside a notch 60.1 formed in an inner surface S60 of inner ring 60. Annular support axial portion 12a is then fitted between the inner surface S60 of the inner ring 6 and the rotor shaft. Further, annular support 12 comprises a radially outwardly extending shoulder 12b extending at the back of axial portion 12a and connecting axial portions 12a and 12c. Shoulder 12b is designed so that a radial gap g2 between impulse ring 10 and sensor element 8 is defined.

Shaft supporting system 2 is assembled as follows. A first step consists in positioning sensor element 8 in annular volume V1 defined by carrier 4, by inserting sensor element 8 from left to right at figure 1 , that is in a direction parallel to radially inwardly extending portion 44. Then, impulse ring 10 is attached to bearing 6 by means of annular support 12 and bearing 6 is positioned aside sensor element 8. Afterwards, carrier 4 is stamped using the process step described above so as to form beading 48. Bearing 6 and sensor element 8 are then axially maintained between beading 48 and collar 46.

Shaft supporting system 2 further includes non-represented wireless communication means for transferring the information measured by sensor element 8 to a non- represented receiver. In the example, this wireless communication means includes a nonrepresented wireless transmitter.

In another non-represented alternative embodiment, wireless communication means may include an antenna for communicating with the receiver via WiFi.

According to another non-represented alternative embodiment, sensor element 8 includes an output cable. This output cable goes through radially inwardly extending portion 44 of carrier 4.

Figure 2 represents a second embodiment of a shaft supporting system 2 according to the invention. The numbers used to reference the elements of the shaft supporting system 2 of figure 2 are the same than those used in figure 1 . Here-below, only the differences with the first embodiment are mentioned for conciseness purpose.

The main difference with the embodiment of figure 1 is that the radially outwardly extending flange 42 and the radially inwardly extending portion 44 are extending from opposite ends of tubular portion 40. Flange 42 is arranged on the side of bearing 6, while portion 44 is arranged at the side of sensor element 8.

In this embodiment, flange 42 is also provided with non represented through holes similar to through holes 042 of the first embodiment.

In a non-represented alternative embodiment, rolling elements 64 may be needles or cylindrical rollers.

In another non-represented alternative embodiment, bearing 6 includes two or more rows of rolling elements.

In another non-represented alternative embodiment, radially outwardly extending flange 42 and radially inwardly extending portion 44 extend from the same end of tubular portion 40.

In another non-represented alternative embodiment, radially outwardly extending flange 42 is fixed to the stator in a different way, such as welding or gluing.

In another non-represented alternative embodiment, impulse ring 10 is axially maintained between inner ring 60 and collar 46.

The technical features of the different embodiments and alternative embodiments of the invention described here-above can be combined together to generate new embodiments of the invention.