WO2010052528A1

WO2010052528A1 - Rolling bearing having an encoder washer, rolling bearing assembly comprising such a rolling bearing and process for manufacturing such a rolling bearing

Info

Publication number: WO2010052528A1
Application number: PCT/IB2008/055638
Authority: WO
Inventors: Franck Landrieve; Sylvain Chaussat
Original assignee: SKF AB
Current assignee: SKF AB
Priority date: 2008-11-06
Filing date: 2008-11-06
Publication date: 2010-05-14
Anticipated expiration: 2011-05-06

Abstract

This rolling bearing (2) comprises an inner ring (22), an outer ring (24), several rolling bodies (26) and a magnetised encoder washer (30). The magnetised encoder washer (30) is directly mounted on one of the rings (22, 24), by magnetic effect (F). The rolling bearing assembly (1 ) comprises the rolling bearing (2) and a sensor (3). According to the process of the invention, one uses a magnetic effect (F) to mount the washer onto one ring (22).

Description

ROLLING BEARING HAVING AN ENCODER WASHER, ROLLING BEARING

ASSEMBLY COMPRISING SUCH A ROLLING BEARING AND PROCESS FOR

MANUFACTURING SUCH A ROLLING BEARING

TECHNICAL FIELD OF THE INVENTION

This invention relates to a rolling bearing comprising, amongst others, a magnetised encoder washer adapted to cooperate with a sensor in order to determine a rotation parameter of the rolling bearing. The invention also relates to a rolling bearing assembly which includes such a rolling bearing. Finally, the invention relates to a process for manufacturing such a rolling bearing.

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.

In the field of rolling bearings, it is known to use a tachymeter in order to determine the rotation speed of a member supported by a rolling bearing. As explained in EP-A-O 992 797, one can use a magnetised multipolar ring of plastoferrite which is supported by a metallic shield immobilized on an internal ring of a rolling bearing. The shield has a complex shape and is thus relatively expensive. Moreover, it is necessary to introduce and immobilize the magnetised ring within a housing of the shield prior to mounting the shield on the ring of the rolling bearing. This is time consuming. On the other hand, the shield is necessary since the plastoferrite of the magnetised ring is brittle and not strong enough to resist static and dynamic efforts in the rolling bearing.

The same problems arise with encoder rings made of relatively soft materials.

SUMMARY OF THE INVENTION

The invention aims at solving these problems with a new rolling bearing having a magnetised encoder washer and where no shield or armature is needed to strengthen this washer.

To this end, the invention concerns a rolling bearing comprising an inner ring, an outer ring, several rolling bodies and a magnetised encoder washer, wherein the magnetised encoder washer is directly mounted on one ring, amongst the inner and the outer ring, by magnetic effect.

Thanks to the invention, the ring on which the magnetised encoder washer is directly mounted by magnetic effect forms an armature for this washer, so that this washer can resist static and dynamic efforts during rotation of the rolling bearing. In other words, the ring of the rolling bearing fulfills the function of the shield of the prior art which makes this shield unnecessary and facilitates manufacturing of the rolling bearing.

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

- The magnetised encoder washer is held on the ring by a magnetic force which is parallel to a rotation axis of the ring. In such a case, the magnetic force advantageously urges the magnetised encoder washer against a lateral face of the ring.

- The magnetised encoder washer is held on the ring by a magnetic force perpendicular to a rotation axis of the ring. In such a case, the magnetic force advantageously urges the magnetised encoder washer against a peripheral inner or outer face of the ring. - The magnetised encoder washer is made of an elastomeric material loaded with ferrite particles, preferably of ferrite nitrile.

- The magnetised encoder washer is made of a thermosetting synthetic resin loaded with ferrite particles, preferably of plastoferhte.

- The magnetised encoder washer is provided with an annular heel for centering it on the ring. The heel might come into abutment against a peripheral face of the ring. Alternatively, a recess can be formed by an annular shoulder between a peripheral face of the ring and a lateral face thereof, the heel being engaged in this recess.

- A sealing member extends between the inner ring and the outer ring, up into the vicinity of the magnetised encoder washer. This sealing member advantageously extends radially, with respect to the rotation axis of the ring, from the other ring towards the heel, up to a distance such that a part of the magnetised encoder washer is axially aligned with a part of the sealing member. The invention also concerns a rolling bearing assembly which comprises a rolling bearing and a sensor, this rolling bearing being as mentioned here-above and the sensor being able to determine a rotation parameter of the rolling bearing by detecting a position or a speed of rotation of the magnetised encoder washer. A rotation parameter of the rolling bearing is a parameter which is representative of the rotation movement of one of the inner or outer rings with respect to the other ring of the rolling bearing. Such a parameter can be an angle measuring the relative angular position of the rings around a central axis of the rolling bearing. Such a parameter can also be a speed, an acceleration or a vibration.

Finally, the invention relates to a process for manufacturing a rolling bearing such as mentioned here-above and, more precisely, to a process for manufacturing a rolling bearing comprising an inner ring, an outer ring, several rolling bodies and a magnetised encoder washer, wherein this process comprises a step of mounting directly the magnetised encoder washer on one of the inner and outer rings, by magnetic effect.

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 longitudinal cut view of a rolling bearing assembly according to the invention including a rolling bearing according to the invention

- figure 2 is a cut view similar to figure 1 for a rolling bearing assembly according to a second embodiment of the invention and

- figure 3 is a cut view similar to figure 1 for a rolling bearing assembly according to a third embodiment of the invention. DETAILED DESCRIPTION OF SOME EMBODIMENTS The rolling bearing assembly 1 represented on figure 1 includes a ball bearing 2 and a sensor 3 adapted to detect the rotation of a part of rolling bearing 2 and to deliver, to a non-represented electronic control unit, an electronic signal S₃ representative of a rotation parameter of ball bearing 2.

Ball bearing 2 comprises an inner ring 22, an outer ring 24 and several balls 26 held in position between rings 22 and 24 by a cage 28.

Rings 22 and 24 are centered on a central axis X2 of ball bearing 2. Outer ring 24 is immobilized within an external support member 4 which has an extension 4A supporting sensor 3.

Ring 22 can rotate around axis X₂ with respect to ring 24. A magnetised encoder washer 30 is mounted on inner ring 22 and located in front of sensor 3 which is adapted to detect the rotation of washer 30, with ring 22, around axis X₂. Sensor 3 can be a Hall effect cell or any other suitable sensor cell. Washer 30 is made of plastoferrite and is magnetised with two poles, namely a north pole N, represented on the upper part of figure 1 , and a south pole S, represented on the lower part of this figure.

A shaft 5 is mounted within ring 22 and fast in rotation with this ring. Shaft 5 does not belong to the invention and is an example of an element whose rotation can be obtained with rolling bearing assembly 1 and ball bearing 2.

Inner ring 22 is made of magnetic steel, preferably a "bearing steel" such as 100Cr6 or 100CrMo7-3, so that washer 30 is urged against a lateral face 23 of ring 22 by a magnetic force F which results from the magnetization of washer 30. This magnetic force F is parallel to axis X₂ and its intensity depends on the magnetization or polarization features of washer 30 and on the material of ring 22. Washer 30 is magnetised in such a way that force F is strong enough to efficiently hold washer 30 on lateral face 23 of inner ring 22, even in the presence of centrifugal forces generated during rotation of inner ring 22.

Other steels, which are commonly used for bearings, such as SAE 1070 or SAE 1055, can also be used to build ring 22.

Once washer 30 is held against lateral face 23 by magnetic force F, ring 22 works as an armature for washer 30 and strengthens it, so that it can resist the dynamic efforts resulting from the rotation of ring 22 and shaft 5, even in case of unbalance of shaft 5.

Washer 30 is provided with a heel 32 which comes into abutment against the outer peripheral or radial face 25 of ring 22. This heel 32 is annular and works as a centering member for washer 30 on ring 22. This centering member facilitates mounting of washer 30 on ring 22. Heel 32 helps positioning washer 30 with respect to ring 32 along a radial direction Y₂ which is perpendicular to axis X₂, in particular when washer is being mounted on ring 22, just before washer 30 lies against face 23, that is when force F is not yet strong enough to avoid radial movements of washer 30 with respect to ring 22.

However, heel 32 is not compulsory and washer 30 may be configured to lie only against lateral face 23 of ring 22. Centering of washer 30 with respect to ring 22 is then made by the operator, possibly with the help of an external guide member which is removed once force F is active to urge washer 30 against face 23.

When ring 22 rotates around axis X₂, it drives washer 30 in rotation because washer 30 is firmly urged against face 23. Rotation of washer 30 induces that poles N and S successively come in front of sensor 3 which can determine a rotation parameter for rolling bearing 2, such as the rotation speed of ring 22. In the second embodiment of the invention represented on figure 2, the elements similar to the ones of the first embodiment have the same references. The rolling bearing assembly 1 of this embodiment includes a ball bearing 2 and a sensor 3. Ball bearing 2 has an inner ring 22 and outer ring 24, several balls 26 and a cage 28. A magnetised washer 30 of ferrite nitrile, that is particles of ferrite embedded in a nitrile matrix, is held against a lateral face 23 of inner ring 22 by a magnetic force F parallel to the axis of rotation X₂ of inner ring 22 which is the moving ring of ball bearing 2, its outer ring 24 being immobilized within a support member 4 provided with an extension 4A which supports sensor 3. In this embodiment, one makes use of the fact that washer 30 has two poles, respectively a north pole N and a south pole S. A shaft 5 is mounted within ring 22.

The internal volume of ball bearing 2 is isolated from the outside by a sealing gasket 42 which has an elastomeric body 421 and a steel armature 422 and extends radially with respect to axis X2, between two recesses 242 and 222, respectively provided in outer ring 24 and inner ring 22.

Washer 30 is provided with an annular heel 32 which helps centering it on inner ring 22. Inner ring 22 is provided with a recess formed by a shoulder 224 in the junction zone between its lateral face 23 and its peripheral outer face 25. This recess 224 has a shape adapted to accommodate heel 32. Close to face 23, ring 22 forms a bead 225 which is in contact with an inner radial face 321 of heel 32 and increases the friction effect between elements 22 and 30. This friction effect helps force F to hold washer 30 on ring 22.

A sealing flange 52 extends radially between rings 22 and 24 and has a hook part 521 blocked within a recess 244 of outer ring 24 and a bended end 522 which is opposite to hook part 521 and extends up into the vicinity of heel 32. di denotes the radial distance between heel 32 and bended end 522. Distance di has a maximum value of 1 mm which is smaller than the radial distance U2 between heel 32 and the outer radial face 34 of washer 30. This implies that an outer radial part 36 of washer 30, which extends radially outside heel 32, is located axially in front of bended end 522 of sealing flange 52, so that it prevents direct entry of impurities within the internal volume of ball bearing 2 in the interstice between heel 32 and bended end 522. In other words, washer 30 and sealing flange 52 form together a labyrinth sealing.

According to a non represented embodiment of the invention, sealing flange 52 could be replaced by a sealing gasket having a lip in sliding contact against heel 32. According to an advantageous aspect of the invention, the geometry of sealing flange 52 can be the same as a sealing flange used for a ball bearing without magnetised encoder washer and whose inner ring is not provided with a recess similar to recess 224. Actually, the bended end 522 of such a sealing flange 52 comes next to the outer face 25 of the inner ring 22 of such a rolling bearing. In other words, the embodiment of figure 2 makes use of components of ball bearing 2 which are identical to the ones of a ball bearing without encoder washer 30, with the exception of inner ring 22. In the third embodiment of the invention represented on figure 3, the elements similar to the ones of the first embodiment have the same references.

The rolling bearing assembly 1 of this embodiment also includes a rolling bearing 2 with an inner ring 22, an outer ring 24 and several rollers 26 located between the inner and outer rings.

Outer ring 24 is held stationary with respect to a support member 4 provided with an extension 4A which also supports a magnetic sensor 3. A shaft 5 is mounted within internal ring 22 and rotates with this ring.

A magnetised encoder washer 30 made of ferrite nitrile is mounted around the outer peripheral or radial face 25 of inner ring 22 and has a northern pole N and a southern pole S. Since ring 22 is made of magnetic steel, a centripetal magnetic force F' firmly urges washer 30 against face 25. Therefore, washer 30 rotates with ring 22 and its rotation can be detected by sensor 3.

As in the first two embodiments, ring 22 forms an armature for washer 30. In all three embodiments, direct mounting of the magnetised encoder washer

30 on the inner ring 22 is fast and easy and does not necessitate the use of a specific tool.

In all embodiments, the inner ring 22 strengthens the magnetised encoder washer 30 without necessity to use an armature or a shield for this washer. The invention has been represented with a magnetised encoder washer mounted on the inner ring of a rolling bearing. However, such a washer could also be mounted on an outer ring of such a bearing, in the case where the outer ring is rotating whereas the inner ring is held stationary. In such a case, the geometry of the heel and of the outer ring is adapted for their cooperation and the washer is centered with respect to the inner peripheral or radial face of the outer ring.

Instead of ferrite nitrile, other resilient materials can be used to make washer 30, in particular an elastomehc material loaded with ferrite particles. Similarly, instead of plastoferrite, one can use other brittle materials, such as a thermosetting synthetic resin loaded with ferrite particles. One can use ferrite nitrile for the washer of the first embodiment or plastoferrite for the washer of the second and third embodiments.

Alternatively, washer 30 can be made exclusively of metal, e.g. as a bipolar or multipolar metallic magnet. The magnetised encoder washer can have more than two poles, e.g. four to twenty-four poles, which induces a more even repartition of the magnetic force F or F' around axis X₂.

The technical features of the embodiments mentioned here-above can be combined within the scope of this invention. In particular, a sealing flange or gasket can be used with the embodiments of figures 1 and 3. Its geometry is adapted to the relative positions of washer 30 and rings 22 and 24 and to the potential use of a heel 32.

In all embodiments, the sensor 3 can be mounted directly on the outer ring 24, instead of the extension 4A.

The invention has been represented with respect to a ball bearing or a roller bearing. It can also be implemented with other rolling bearings, such as needle bearings.

Claims

1. A rolling bearing (2) comprising an inner ring (22), an outer ring (24), several rolling bodies (26) and a magnetised encoder washer (30), wherein said magnetised encoder washer (30) is directly mounted on one ring (22), amongst said inner and outer rings (22, 24), by magnetic effect (F, F').

2. Rolling bearing according to claim 1 , wherein said magnetised encoder washer (30) is held on said ring (22) by a magnetic force (F) parallel to a rotation axis (X₂) of said ring (22).

3. Rolling bearing according to claim 2, wherein said magnetic force (F) urges said magnetised encoder washer (30) against a lateral face (23) of said ring (22).

4. Rolling bearing according to claim 1 , wherein said magnetised encoder washer (30) is held on said ring (22) by a magnetic force (F') perpendicular to a rotation axis (X₂) of said ring (22).

5. Rolling bearing according to claim 4, wherein said magnetic force (F') urges said magnetised encoder washer (30) against a peripheral inner or outer face (25) of said ring (22).

6. Rolling bearing according to one of the previous claims, wherein said magnetised encoder washer (30) is made of an elastomeric material loaded with ferrite particles, preferably of ferrite nitrile.

7. Rolling bearing according to one of claims 1 to 5, wherein said magnetised encoder washer (30) is made of a thermosetting synthetic resin loaded with ferrite particles, preferably of plastoferrite.

8. Rolling bearing according to one of the previous claims, wherein said magnetised encoder washer (30) is provided with an annular heel (32) for centering said washer on said ring (22).

9. Rolling bearing according to claim 8, wherein said heel (32) comes into abutment against a peripheral face (25) of said ring (22).

10. Rolling bearing according to claim 8, wherein a recess is formed by an annular shoulder (224) between a peripheral face (25) of said ring (22) and a lateral face (23) of said ring, said heel (32) being engaged in said recess.

11. Rolling bearing according to one of the previous claims, wherein a sealing member (52) extends between said inner ring (22) and said outer ring (24), up into the vicinity of said magnetised encoder washer (30).

12. Rolling bearing according to one of claims 8 to 10 and to claim 11 , wherein said sealing member (52) extends radially, with respect to the rotation axis (X₂) of said ring (22), from the other ring towards said heel (32) up to a distance (di) such that a part (36) of said magnetised encoder washer (30) is axially aligned with a part (522) of said sealing member.

13. A rolling bearing assembly (1 ) comprising a rolling bearing (2) and a sensor (3), said rolling bearing (2) being according to one of the previous claims and said sensor (3) being able to determine a rotation parameter of said rolling bearing by detecting a position or speed of rotation of the magnetised encoder washer (30).

14. A process for manufacturing a rolling bearing (2) comprising an inner ring (22), an outer ring (24), several rolling bodies (26) and a magnetised encoder washer (30), wherein said process comprises a step of mounting directly said magnetised encoder washer (30) on one (22) of said inner and outer rings (22, 24), by magnetic effect (F, F').