WO2010070392A1

WO2010070392A1 - Rolling bearing assembly with an encoder washer and a sensor, and process for manufacturing such a rolling bearing assembly

Info

Publication number: WO2010070392A1
Application number: PCT/IB2008/055678
Authority: WO
Inventors: Franck Debrailly; Vincent Sausset
Original assignee: Aktiebolaget Skf
Priority date: 2008-12-16
Filing date: 2008-12-16
Publication date: 2010-06-24

Abstract

This rolling bearing assembly (2) comprises a rolling bearing (4) with a first non rotating ring (42), a second ring (44) rotating with respect to the first ring around an axis of rotation (X₄) and rolling bodies between the first and second ring. The assembly also comprises an encoder washer (6) fast in rotation with the second ring (44), and at least one sensor (8) adapted to detect a rotation parameter of the encoder washer (6), the sensor being located axially at the same level as the encoder washer (6). The rolling bearing assembly (2) also comprises mechanical setting means (14, 16) to adjust a radial distance between the sensor (8) and the encoder washer (6).

Description

ROLLING BEARING ASSEMBLY WITH AN ENCODER WASHER AND A SENSOR, AND PROCESS FOR MANUFACTURING SUCH A ROLLING

BEARING ASSEMBLY

TECHNICAL FIELD OF THE INVENTION

This invention relates to a rolling bearing assembly comprising, amongst others, an encoder washer fast in rotation with a rotating ring and adapted to cooperate with a sensor in order to determine a rotation parameter of the rolling bearing assembly. The invention also relates to a process for manufacturing 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 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 tachometer in order to determine the rotation speed of a member supported by a rolling bearing. As explained in EP-A-1 993 155, one can use an encoder washer fast in rotation with a rotating ring of the bearing and several sensors distributed around the encoder washer and mounted onto a foldable printed circuit board installed within an outer body. The accuracy of the detection obtained by the respective sensors depends, amongst others, on the thickness of a radial air gap between the encoder washer and each sensor. In order to obtain an acceptable accuracy on the measure of an angular position of the rotating ring and because of variations in the thickness of such radial air gaps, one must use sensors with an adjustable gain and set the gain of each sensor. Such sensors with adjustable gains are expensive and the step of electronic calibration of such sensors requires a qualified manpower and is time consuming.

SUMMARY OF THE INVENTION

The invention aims at solving these problems with a new rolling bearing assembly which allows to accurately determine a rotation parameter, without having to use adjustable gain sensors. To this end, the invention concerns a rolling bearing assembly comprising a rolling bearing with a first non-rotating ring, a second ring rotating with respect to the first ring around an axis of rotation, rolling bodies between the first and second ring, an encoder washer fast in rotation with the second ring and at least one sensor adapted to detect a rotation parameter of the encoder washer, this sensor being located axially at the same level as the encoder washer. This rolling bearing assembly is characterized in that it comprises some mechanical setting means to adjust a radial distance between the sensor and the encoder washer.

In the present description, the words "axial", "radial", "axially", "radially", "centrifugal" and "centripetal" relate to the axis of rotation of the second ring with respect to the first 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 distance is measured radially with respect to the axis of rotation.

Thanks to the invention, the mechanical setting means can be used in order to precisely install the or each sensor with respect to the encoder washer, so that the radial air gap between this sensor and the encoder washer has a value which allows an efficient detection of the rotation or position of this washer by the or each sensor, without a need to use complex and expensive electronic equipments.

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 rolling bearing assembly comprises several sensors and the mechanical setting means can adjust independently the radial distance between each sensor and the encoder washer. Advantageously, the mechanical setting means include one adjustment member per sensor.

- The sensor is installed radially outside the encoder washer and the mechanical setting means exert a centripetal adjustable effort and an elastic centrifugal effort on the or each sensor. Alternatively, the sensor is installed radially inside the encoder washer and the mechanical setting means exert an adjustable centrifugal effort and an elastic centripetal effort on the or each sensor.

- The elastic effort is exerted by a spring making a loop of more than 180° preferably more than 270° around the rotation axis . Such a spring is advantageously provided with at least one locally curved zone adapted to go around a detection cell of each sensor, in such a way that the spring does not interfere with the detection cell.

- The mechanical setting means comprise at least one screw inserted within a threaded hole of a body located axially at the same level as the encoder washer, the screw being adapted to come into abutment against the sensor.

- Alternatively, the mechanical setting means comprise at least a pin with inclined toothing, this pin being inserted within a hole of a body located axially at the same level as the encoder washer, the pin being adapted to come into abutment against the sensor and being movable within the hole in one direction only.

- The rolling bearing assembly comprises several sensors mounted on a foldable printed circuit board, the foldable printed circuit board being mounted within a body which holds at least some of the mechanical setting means. Alternatively, the rolling bearing assembly comprises several sensors connected by flexible electrical conductors and mounted within a body which holds at least some of the mechanical setting means.

- The body is provided with at least one recess adapted to accommodate at least a part of one sensor, whereas one mechanical adjustment member is located next to the or each recess and adapted to adjust the radial distance between the encoder washer and a sensor received at least partially within this recess.

The invention also relates to a process for manufacturing a rolling bearing assembly as mentioned here-above. This process comprises a step of installing the sensor axially at the same level as the encoder washer and it is characterized in that it further comprises at least a step of mechanically adjusting the radial distance between the sensor and the encoder washer.

According to a first advantageous aspect of the invention, when the rolling bearing assembly comprises several sensors, the radial distance between each sensor and the encoder washer is adjusted individually.

According to another advantageous aspect of the invention, the radial distance between the or each sensor and the encoder washer is adjusted on the basis of a comparison between an output signal of the sensor and a reference value. 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 rolling bearing assembly according to the invention, - figure 2 is a cut view, at a larger scale, along plane Il on figure 1 ,

- figure 3 is a sectional view, at a smaller scale, along line Ill-Ill on figure 2,

- figure 4 is a perspective exploded view of the rolling bearing assembly of figures 1 to 4, and

- figure 5 is a perspective exploded view similar to figure 4 for a rolling bearing assembly according to a second embodiment of the invention.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

The rolling bearing assembly 2 represented on figures 1 to 4 includes a rolling bearing 4 having an outer ring 42, an inner ring 44 and several balls 46 rolling between rings 42 and 44. A cage 48 holds the balls 24 in position in a radial volume V₄ defined between rings 42 and 44. A sealing gasket 43 closes volume V₄ on one lateral side.

Outer ring 42 is supposed to be held fast, whereas inner ring 44 rotates with respect to outer ring 44 around a central axis X₄ of rolling bearing 4. This rotation is possible thanks to balls 46.

Rolling bearing assembly 2 also comprises means to determine a rotation parameter of inner ring 44 with respect to outer ring 42. These means include an encoder washer 6 formed of an active part 62 and an armature 64. Part 62 is magnetized and defines along its circumference an alternation of North poles N and South poles S, respectively formed by permanent magnets. In the simplest configuration represented on figures 1 to 4, there is only 1 pair of poles, that is to say that the encoder washer is bipolar. Active part 62 is fixedly mounted on armature 64 and armature 64 is fixedly mounted on the outer radial surface 442 of inner ring 44. A flange 642 of armature 64 is clipped onto surface 442. Thus, encoder washer 6 is fast in rotation with inner ring 44 and rotates with this ring around axis X₄. Because of the North and South poles of active part 62, the rotation of ring 44 induces variations in an electromagnetic field radially surrounding encoder washer 6.

Encoder washer 6 is associated to five sensors 8 mounted on a foldable printed circuit board 10 in the form of a strip. Printed circuit board 10 has five rigid zones 102, each zone 102 supporting a sensor 8, and four flexible zones 104, each zone 104 connecting two zones 102 and including flexible electrical conductors such as conducting tracks. Printed circuit board 10 bears a connector 106 adapted to be connected to a non-represented connector of a non- represented electronic control unit. Printed circuit board 10 can be folded as represented on figure 4 where its inner face 108 is directed towards axis X₄, whereas its outer face 109 is directed away from this axis.

Each sensor 8 includes a main portion 82 located on the outer face 109 of a rigid zone 102 and a detection cell protruding from the inner face 108 of said rigid zone. Parts 82 and 84 of sensor 8 are connected through one or several holes in printed circuit board 10. Items 6, 8 and 10 form together means to determine a rotation parameter of ring 44 around axis X₄. Such a parameter can be an angle, measuring the angular position of ring 44 with respect to ring 42, around central axis X₄. Such a parameter can also be a speed, a displacement, an acceleration or a vibration.

Alternatively to a magnetized washer, washer 6 can include an active part made of a magnetic metal and provided with notches or holes whose movements can be detected by sensors such as inductive sensors.

When it is equipped with sensors 8, printed circuit board 10 is installed within a support body 12 made of plastic material and which is provided with five recesses 122 each adapted to accommodate each a main portion 82 of one sensor 8 when printed circuit board is in the folded configuration of figure 4. Support body 12 has a radial outer wall 124, a radial inner wall 125 and a lateral wall 126 connecting outer and inner walls 124 and 125, wall 126 being perpendicular to axis X₄. Recesses 122 are formed on the inner side 124B of outer wall 124.

Support body 12 is provided with five threaded holes 128, each hole 128 crossing outer wall 124, from its outer face 124A to its inner face, at the level of the bottom surface 122A of a recess 122.

One screw 14 is inserted within each hole 128 and extends along a radial direction with respect to axis X₄.

Depending on how deep a screw 14 is screwed within a hole 128, its inner end can more or less protrude from surface 122A within a recess 122 and come into abutment with the main portion 82 of a sensor 8.

Lateral wall 126 is provided with a hole 127 through which connector 106 extends to the outside of body 12, on a lateral face of assembly 2, as shown on figure 1. This facilitates connection of sensors 8 to the electronic control unit.

A spring 16 is made by rod folded with a globally pentagonal shape corresponding to the globally pentagonal shape of printed circuit board when it is installed within body 12. Spring 16 has five portions 162 which are flat when seen in the direction of axis X₄ and four portions 164 which connect two portions 162 and make each an angle of about 72°. Therefore, eac h portion 162 can lie against the inner face 108 of a rigid zone 102 of printed circuit board 10, at the level of a sensor 8. In other words, spring 16 can be laid against all sensors 8 through printed circuit board 10.

Each portion 162 is provided with a central curved zone 166 which is in the same plane as the remaining part of portion 162 and designed to go around a detection cell 84 when spring 16 is installed radially within printed circuit board and lies against a sensor 8.

Spring is designed and shaped to exert on printed circuit board 10 a centrifugal effort Ei which pushes printed circuit board 10 and sensors 8 against the inner face 124B of wall 124 and the bottom surfaces 122A of recesses 122.

Spring 16 makes a loop on an angle α of about 330° around axis X₄. Depending on the number of sensors 8, which can be different from 5, spring 16 can make a loop on an angle α which can be smaller. However, this angle is larger than 180° preferably larger than 270° in order to ensure an effective holding of spring 16 within board 10 and a regular or quasi-regular repartition of effort Ei around axis X₄. On figure 4, effort Ei is represented at several locations around axis X₄. Effort Ei is actually spread around axis X₄, but for the zone between the two ends 168 of spring 16.

A metallic armature 18 forms an outer radial shell for support body 12 which is received in the inner volume of armature 18. Armature 18 is provided with five radial holes 182 giving access to screws 14 when they are inserted within threaded holes 128. In other words it is possible to drive screws 14 in rotation through holes 182, when these screws are within holes 128. Actually, the diameter of holes 182 can be larger than the diameter of holes 128, so that screws 14 can be introduced within holes 128 through holes 182.

Armature 18 is designed and shaped to be blocked on an inner recess 422 of outer ring 42 in such a way that armature 18 and body 12 are fast in rotation with ring 42. Armature 18 has a flange 184 shaped to be blocked or clipped within recess 422 by cooperation of shapes. In this configuration represented on figures 1 to 3, sensors 8 are axially aligned with washer 6. In other words, sensors 8 are located at the same level as washer 6 along axis X₄. Sensors 8, and in particular their detection cells 84 should then be in a position to efficiently detect the angular position of the North and South poles N and S of washer 6.

In order for these sensors to be efficient, the sensors 8 must be located with respect to the encoder washer 6 in a position such that a radial air gap G between the outer radial surface 626 of active part 62 and each detection cell 84 has a predetermined value.

Thanks to screws 14, it is possible to exert on the outer face 822 of the main portion 82 of a sensor 8 a centripetal effort E₂ which tends to move sensor 8, and in particular its detection cell 84, towards encoder washer 6 and axis X₄. Effort E₂ overbalances effort Ei in order to move a sensor 8 towards axis X₄.

In other words, screws 14 allow to adjust the radial distance U_G between each sensor 8 and encoder washer 6, that is the thickness of air gap 6, in such a way that it is possible to use sensors 8 with a fixed gain. The adjustment of the position of a sensor 8 with respect to encoder washer

6 is made individually, that is sensor by sensor, insofar as one screw 14 is provided for each sensor 8. This enables to have different values of air gap thickness dσ for different sensors 8 of a same rolling bearing assembly 2, as shown on figure 3. This is to be compared to the fact that the intrinsic features of the sensors 8 can vary from one sensor to another.

Spring 16 is advantageous insofar as it resists effort E₂ and holds main portions 82 within recesses 122. However, spring 16 is not compulsory and one can adjust the position of the sensors 8 with respect to encoder washer 6 by using only screws 14, provided that printed circuit board 10 is flexible enough to hold sensors 8 within recesses 122 and to exert effort Ei .

The determination of radial distance dσ to be used between each sensor 8 and the encoder washer 6 can be made by measuring the output signal of one sensor 8 for a given position of inner ring 44 and comparing it to the output signal of an external reference sensor. Depending on the result of this comparison the corresponding screw 14 can be further screwed or unscrewed in the corresponding threaded hole 128, which allows to adjust the position of this sensor 8 to a position where its output signal is similar or very close to the output signal of the reference sensor. Alternatively, one of the sensors 8 can be taken as the reference sensor, and then all the other sensors 8 are adjusted with respect to that reference sensor.

In the second embodiment of the invention represented on figure 5, the elements similar to the ones of the first embodiment have the same references. The rolling assembly 2 of this embodiment also has a rolling bearing 4, an encoder washer 6, a support body 12, five screws 14, a spring 16 and an armature 18, these elements being the same as in the first embodiment. Five sensors 8 are connected by flexible cables 20 and can be installed within the recesses 122 of body 12 as in the first embodiment. In other words, one uses discrete sensors 8 connected by flexible cables 20 instead of a printed circuit board 10 as in the first embodiment. Spring 16 holds sensors 8 in their respective recesses 122 of support body 12. The position of each sensor 8 can be set thanks to screws 14 in order to adjust the radial distance between each sensor 8 and the encoder washer 6. In other words, the assembly of the second embodiment works substantially in the same way as the assembly of the first embodiment.

For all embodiments, insofar as the position of a sensor 8 is normally adjusted once during manufacturing of the rolling bearing assembly, the position of each screw 14 can be fixed permanently by using glue at the interface between screws 14 and threaded holes 128. Alternatively, screws 14 can be provided with self-locking threads.

According to another embodiment of the invention, which is not represented, screws 14 can be replaced by pins provided with an inclined toothing adapted to cooperate with an internal relief of holes located as holes 128 on figures 4 and 5, which implies that the pins can be pushed radially towards axis X₄ and are blocked in a centrifugal direction. In other words, the pins can be moved within the holes in one direction only, in order to adjust the position of the sensors 8.

The invention has been represented when used with five screws 14. The number of screws or pins can be different from five, preferably between two and eight. The shape of spring 16 and its angle α are adapted to the number of screws or pins.

The invention has been represented with a rolling bearing having a fixed outer ring 42 and a rotating inner ring 44. Alternatively, the rolling bearing can have a fixed inner ring and a rotating outer ring.

According to a non-represented embodiment of the invention, the sensors can be located radially inside the encoder washer 6. In such a case, the screws 14 or pins exert a centrifugal effort and the spring 16 exerts a centripetal effort.

The invention can be implemented with any kind of rolling bearing, in particular a ball bearing, a roller bearing or a needle bearing.

Claims

1. A rolling bearing assembly (2) comprising:

- a rolling bearing (4) with a first non rotating ring (42), a second ring (44) rotating with respect to the first ring around an axis of rotation (X₄) and rolling bodies (46) between the first and second rings,

- an encoder washer (6) fast in rotation with the second ring (44), and

- at least one sensor (8) adapted to detect a rotation parameter of the encoder washer, the sensor being located axially at the same level as the encoder washer, wherein the rolling bearing assembly comprises mechanical setting means (14, 16) to adjust a radial distance (dσ) between the sensor (8) and the encoder washer (6).

2. Rolling bearing assembly according to claim 1 , wherein it comprises several sensors (8) and the mechanical setting means (14, 16) can adjust independently the radial distance between each sensor (8) and the encoder washer (6).

3. Rolling bearing assembly according to claim 2, wherein the mechanical setting means include one adjustment member (14) per sensor (8).

4. Rolling bearing assembly according to any one of the previous claims, wherein the sensor (8) is installed radially outside the encoder washer (6) and the mechanical setting means (14, 16) exert a centripetal adjustable effort (E₂) and an elastic centrifugal effort (Ei) on the or each sensor (8).

5. Rolling bearing assembly according to any one of claims 1 to 3, wherein the sensor (8) is installed radially inside the encoder washer and the mechanical setting means (14, 16) exert an adjustable centrifugal effort and an elastic centripetal effort on the or each sensor.

6. Rolling bearing assembly according to one of claims 4 or 5, wherein the elastic effort is exerted by a spring (16) making a loop on an angle (α) of more than 180° preferably more than 270° around the ro tation axis (X₄).

7. Rolling bearing assembly according to claim 6, wherein the spring (16) is provided with at least one locally curved zone (166) adapted to go around a detection cell (84) of each sensor (8), in such a way that the spring does not interfere with the detection cell.

8. Rolling bearing assembly according to any one of the previous claims, wherein the mechanical setting means comprise at least one screw (14) inserted within a threaded hole (128) of a body (12) located axially, at the same level as the encoder washer (6), the screw being adapted to come into abutment against the sensor (8).

9. Rolling bearing assembly according to any one of claims 1 to 7, wherein the mechanical setting means comprise at least a pin with an inclined toothing, the pin being inserted within a hole of a body (12) located axially, at the same level as the encoder washer (6), the pin being adapted to come into abutment against the sensor (8) and being movable within the hole in one direction only.

10. Rolling bearing assembly according to any one of the previous claims, wherein it comprises several sensors (8) mounted on a foldable printed circuit board (10), the foldable printed board being mounted within a body (12) which holds at least some (14) of the mechanical setting means.

11. Rolling bearing assembly according to any one of claims 1 to 9, wherein it comprises several sensors (8) connected by flexible electrical conductors (20) and mounted within a body (12) which holds at least some (14) of the mechanical setting means.

12. Rolling bearing assembly according to one of claims 10 and 11 , wherein the body (12) is provided with at least one recess (122) adapted to accommodate at least a part (82) of one sensor (8), and wherein one mechanical adjustment member (4) is located next to the or each recess and adapted to adjust the radial distance (d_G) between the encoder washer (6) and a sensor received at least partially within said recess.

13. A process for manufacturing a rolling bearing assembly comprising:

- a rolling bearing (4) with a first non-rotating ring (42), a second ring (44) rotating with respect to the first ring around an axis of rotation (X₄) and rolling bodies (46) between the first and second ring, - an encoder washer (6) fast in rotation with the second ring, and

- at least one sensor (8) adapted to detect a rotation parameter of the encoder washer, the process comprising a step of installing the sensor (8) axially at the same level as encoder washer (6) wherein the process further comprises at least a step of mechanically adjusting the radial distance (dσ) between the sensor (8) and the encoder washer (6).

14. Process according to claim 13, wherein the rolling bearing assembly comprises several sensors (8) and the radial distance (dσ) between each sensor

(8) and the encoder washer (6) is adjusted individually.

15. Process according to one of claims 13 or 14, wherein the radial distance (d_G) between the or each sensor (8) and the encoder washer (6) is adjusted on the basis of a comparison between an output signal of the sensor and a reference value.