WO2012080779A1

WO2012080779A1 - Rotation detection set, bearing assembly including such a rotation detection set and apparatus equipped with such a bearing assembly

Info

Publication number: WO2012080779A1
Application number: PCT/IB2010/003526
Authority: WO
Inventors: Sylvain Chaussat; Vincent Sausset
Original assignee: Aktiebolaget Skf
Priority date: 2010-12-17
Filing date: 2010-12-17
Publication date: 2012-06-21

Abstract

This rotation detection set (20, 40) comprises an encoder washer (20), adapted to rotate around a rotation axis (X2), at least one sensor adapted to detect a rotation parameter of the encoder washer, and a support member (44) holding the sensor with respect to the rotation axis (X2). The support member (44) is provided with a relief (448) adapted to cooperate with a relief (204) of a fixed part (B) in order to immobilize the support member (44) in rotation around the rotation axis (X2). The bearing assembly (A) comprises a bearing (2), with a fixed ring (4) and a rotatable ring (6), and a rotation detection set (20, 40), whose encoder washer (20) is fast in rotation with the rotatable ring (6) whereas the support member (44) is mounted on the fixed ring (4). An apparatus, equipped with such a bearing assembly (A), has a fixed part (B) provided with a relief (204) adapted to cooperate with the relief (448) of the support member (44) in order to immobilize the support member in rotation around the rotation axis (X2).

Description

ROTATION DETECTION SET, BEARING ASSEMBLY INCLUDING SUCH A ROTATION DETECTION SET AND APPARATUS EQUIPPED WITH SUCH A BEARING

ASSEMBLY TECHNICAL FIED OF THE INVENTION

This invention relates to a rotation detection set used to detect a rotation parameter of an encoder washer rotating around a rotation axis. Such a set is particularly useful for detecting the rotation of a rotatable ring of a bearing with respect to a fixed ring.

This invention also relates to a bearing assembly comprising, amongst others, a rotation detection set as mentioned here-above. Finally, the invention relates to an apparatus equipped with such a bearing assembly.

BACKGROUND OF THE INVENTION

Generally speaking, a bearing comprises an inner ring and an outer ring adapted to rotate around a rotation axis, one with respect to the other. In a plain bearing, the two rings are in sliding contact. In a rolling bearing, several rolling bodies are installed between the two rings. These rolling bodies can be balls, rollers or needles. Thus, a rolling bearing can be, for instance, a ball bearing, a roller bearing or a needle bearing.

In the field of bearings, it is known to use a tachometer in order to determine the rotation speed of a member supported by a bearing. As explained in EP-A-1 933 155, one can use an encoder washer with magnetic poles, fast in rotation with a rotatable ring of a bearing, and one or several sensors distributed around the rotation axis of the encoder washer. This or these sensor(s) are held in position with respect to the rotation axis of the encoder washer by a support member which is supposed to be mounted on a fixed part, e.g. the fixed ring of a bearing. However, during the lifetime of a rotation detection set, the angular position of known support members with respect to the rotation axis may vary, especially when it is mounted on a fixed ring of a bearing. Actually, such a fixed ring is usually housed within a circular recess of a fixed structure. Because of vibrations, the fixed ring might actually rotate within the corresponding recess, which induces a rotation of the support member and, thus, of the sensor(s). This might have a negative influence on the accuracy of the rotation detection obtained with known devices.

SUMMARY OF THE INVENTION

The invention aims at solving these problems with a new rotation detection set which guarantees that the or each sensor is reliably held in position with respect to the rotation axis of the encoder washer. To this end, the invention concerns a rotation detection set comprising an encoder washer, adapted to rotate around a rotation axis, at least one sensor, adapted to detect a rotation parameter of the encoder washer, and a support member holding the sensor with respect to the rotation axis. According to the invention, the support member is provided with a relief adapted to cooperate with a relief of a fixed part in order to immobilize the support member in rotation around the rotation axis of the encoder washer.

Thanks to the invention, the relief of the support member blocks the support member in rotation around the rotation axis of the encoder washer, which avoids a rotation of the sensor(s) around this axis. Thus, the position of the sensors with respect to the rotation axis remains unchanged during the lifetime of the rotation detection set.

In the present description, unless otherwise specified, the words "axial", "radial", "axially" and "radially" relate to an axis which can be the axis of rotation of the encoder washer or a central axis defined by the support member. A direction is "axial" when it is parallel to such an axis and a direction or an axis is "radial" when it is perpendicular to and secant with such an axis.

According to further aspects of the invention which are advantageous but not compulsory, the rotation detection set might incorporate one or several of the following features, taken in any technically admissible configuration:

- The support member is circular or arcuate and centered on the rotation axis and the relief of this support member is provided on a radial outer or inner surface of this support member.

- Alternatively, the relief of the support member is provided on a front face of the support member which is perpendicular to the rotation axis.

- The support member is made of molded synthetic material and its relief is integral with the support member.

- The relief of the support member protrudes from a face of the support member. This relief is advantageously at least partially elastically deformable. In particular, it might have at least two deformable ribs separated by a groove, these ribs being adapted to be elastically pushed towards each other when they are received within a corresponding recess of a fixed part.

- The rotation detection device includes an electrically conductive member, the support member defines a housing adapted to accommodate an end of a cable connected, directly or via a printed circuit board, to the sensor, the support member has a hollow protrusion whose internal volume connects the housing of the support member to a zone defined by this support member and adapted to accommodate the electrically conductive member and the relief of the support member is formed by this hollow protrusion. Advantageously, this part of the hollow protrusion is elastically deformable.

The invention also concerns a bearing assembly comprising a bearing, with a fixed ring and a rotatable ring, and a rotation detection set as mentioned here-above, the encoder washer of this rotation detection set being fast in rotation with the rotatable ring and the support member being mounted on the fixed ring of this bearing.

Finally, the invention concerns an apparatus equipped with bearing assembly as mentioned here-above, this apparatus having a fixed part provided with a relief adapted to cooperate with the relief of the support member in order to immobilize the support member in rotation around an axis of rotation of the rotatable ring of the bearing and the encoder washer of the rotation detection device.

Advantageously, the fixed part surrounds an outer ring of the bearing, the relief of the fixed part is a recess provided on a radial inner edge of this fixed part and the relief of the support member extends radially outwardly with respect to this outer ring.

Alternatively or in addition, the fixed part can surround at least one portion of the rotation detection device, the relief of this fixed part being a recess provided on a radial inner edge of this fixed part, whereas the relief of the support member extends radially outwardly with respect to the above-mentioned portion of the rotation detection device. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be well 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 bearing assembly according to the invention and a part of an apparatus according to the invention,

figure 2 is a top view of the bearing assembly shown on figure 1 ,

figure 3 is an exploded perspective view of the rolling bearing assembly of figures 1 and 2,

figure 4 is an exploded perspective view of a rotation detection device of a rotation detection set belonging to the rolling bearing assembly of figures 1 to 3, figure 5 is a perspective view of a support member and a cable belonging to the rotation detection device of figure 4, viewed from an angle different from figure 4, figure 6 is a perspective view of the support member represented on figure 5, from another angle,

- figure 7 is a cut and perspective view of the support member of figures 5 and 6 taken along line VII-VII on figure 5, figure 8 is a perspective exploded view similar to figure 1 for a second embodiment of the invention,

figure 9 is a perspective view of a rolling bearing assembly according to a third embodiment of the invention,

figure 10 is a perspective view similar to figure 9 for a fourth embodiment of the invention,

figure 1 1 is a perspective view similar to figure 9 for a fifth embodiment of the invention, and

figure 12 is a perspective view similar to figure 9 for a sixth embodiment of the invention.

DESCRIPTION OF SOME EMBODI MENTS

The rolling bearing assembly A represented on the figures comprises a rolling bearing 2 having a fixed outer ring 4 and an inner ring 6 rotating around a central axis X2 of rolling bearing 2. Several balls forming rolling bodies are received within a chamber defined between rings 4 and 6. These balls are held in position with respect to these rings by a cage.

An encoder washer 20 is fast in rotation with inner ring 6 and comprises a metallic armature 22 and a magnetic body 24 which defines several magnetic North poles N and South poles S. Encoder washer 20 is centered on an axis X20 superimposed with axis X2 when encoder washer 20 is mounted onto inner ring 6 by snapping of armature 22 within an inner peripheral groove 6A of ring 6.

A sensing device 40 is mounted onto ring 4 in order to detect a rotation parameter of encoder washer 20, thanks to the variable magnetic field generated by this washer upon rotation. A rotation parameter can be a position, a speed, an acceleration or any other parameter representative of the rotation of encoder washer 20 around axes X2 and X20.

Sensing device 40 includes an annular electrically conductive flange 42 having a peripheral skirt 422 adapted to be snapped within an outer groove 4A of outer ring 4 which is electrically conductive. Thus, when rolling bearing 2 is grounded, by contact of ring 4 with a grounded part, flange 42 mounted onto ring 4 is also grounded. Items 42 and 4 are advantageously metallic.

Rolling bearing assembly is supposed to be mounted onto a fixed body B which belongs to a non represented apparatus, such as a rotary electrical machine, for instance an electric motor. Body B is fastened to a non represented frame of the apparatus and has a circular central through hole 200 with a diameter D200 slightly larger than the outside diameter D2 of rolling bearing 2. Thus, rolling bearing 2 can be received within hole 200 which forms a recess for this bearing. Alternatively, body B can be provided with a blind hole forming a recess adapted to accommodate bearing 2.

X200 denotes the central axis of through hole 200. Axes X2 and X200 are superimposed when bearing 2 is received within through hole 200.

The annular wall 202 of body B which surrounds through hole 200 is provided with a nick or slot 204.

Flange 42 is centered on an axis X42 which is superimposed with axis X2 when sensing device 40 is mounted on rolling bearing 2. Flange 42 is provided with a flat wall 424, perpendicular to axis X42 and provided with an oblong opening or through hole 426, of an arcuate shape centered on axis X42.

Sensing device 40 also includes a support member 44 of an arcuate shape, having an inner wall 441 in the form of a section of a circular cylinder centered on an axis X44 which is superimposed with axes X2 and X42 when support member 44 is mounted onto flange 42 and sensing device 40 is mounted onto ring 4. Support member 44 also has an outer wall 442, which is parallel to inner wall 441 , and a flat wall 443 which is perpendicular to axis X44 and lies against flat wall 424 when support member 44 is mounted onto flange 42. Flat wall 443 connects inner wall 441 to outer wall 442.

Three circular holes 428 are also provided on wall 424 in order to guaranty a robust mechanical anchorage of the support member 44 onto the flange 42. Indeed, when the support member 44 is overmoulded onto the flange 42, some plastic material will flow through the holes 428 and remain there after solidification.

The geometry of support member 44 is defined in connection to axis X44. For the parts of support member 44, the words "axial" or "radial" are defined with respect to this axis.

Support member 44 has an extension 445 which protrudes from the face of wall 443 which lies against wall 424 in the mounted configuration of support member 44 onto flange 42. The global shape of extension 445 is such that it can be inserted within opening 426. Extension 445 is arcuate and centered on axis X44. The inside volume V₄₄₅ of extension 445 defines five slots S ₅ separated by four ribs 446. A holder 46 holds five sensors in a position such that they can be inserted together within volume V₄₄₅, with one sensor in each slot S₄₄₅. Figure 4 shows four sensors, with references 48A, 48B, 48C and 48E, the fifth sensor being omitted to show holder 46. Holder 46 also holds a printed circuit board or PCB 49 and the sensors are connected to this PCB via their respective pins.

When all sensors are received within volume V₄₄₅, PCB 49 is received within a volume V₄₄₃ defined by support member 44 above wall 443, that is between walls 441 and 442, on the side of wall 443 opposite to extension 445. Thus, volume V₄₄₃ forms a housing for PCB 49.

Support member 44 defines a zone Z₄₄ where flange 42 is partly accommodated when support member 44 is mounted onto flange 42. Zone Z₄₄ is defined between extension 445 and a part 441A of wall 441 which extends from wall 443, in the same direction as extension 445. Considering the position of support member on figures 4 and 5, part 441A can be considered as the lower part of wall 441 which extends below wall

443, as extension 445.

Support member 44 is also provided with a hollow protrusion 448 which protrudes outwardly with respect to wall 442, in a direction radial with respect to axis X44. V₄₄₈ denotes the internal volume of protrusion 448. 442A denotes the upper edge of wall 442 that is the edge of wall 442 which is opposite to wall 443. Protrusion 448 has a part 448A which extends from wall 443, opposite to edge 442A. Zone Z₄₄ is defined also between wall part 441 A and protrusion part 448A.

Part 448A is provided with two ribs 448B separated by a groove 448C parallel to axis X44. Ribs 448B extends outwardly from part 448A, that is in a direction away from wall 441 and from zone Z₄₄.

On its side oriented towards wall 441 , part 448A is provided with an opening 448D which connects volume V₄₄₈ to zone Z₄₄.

On the other hand, wall 442 defines the outer radial part of hollow protrusion 448 between wall 443 and edge 442A. An opening 448E extends between wall 443 and edge

442 and connects volumes V₄₄₃ and V₄₄₈.

As shown on figure 5, hollow protrusion 448 extends along wall 442, insofar as it protrudes radially outwardly with respect to axis X44 from this wall.

When support member 44 is mounted onto flange 42, part 448A of protrusion 448 extends radially outwardly with respect to flange 42. As flange 42 has an external diameter D42 which is equal to diameter D2, part 448A also protrudes radially outwardly with respect to the outer radial surface 4B of outer ring 4 when sensing device 40 is mounted onto rolling bearing 2.

In other words, protrusion 448 extends radially with respect to axes X2 and X44 on a distance shown by radius R448 on figure 2 which is larger than half of diameter D2.

As a consequence, when bearing 2 is introduced within recess 200, ribs 448B are inserted within nick 204, so as they prevent rotation of rolling bearing assembly A around axes X2 and X200 within recess 200. In other words, nick 204 forms a recess for ribs 448B in such a way that support member 44 and all parts supported by this member are blocked in rotation around axes X2 and X200. W204 denotes the width of nick 204, that is the distance between two walls parallel to axis X200 which define the sides of nick 204. W448 denotes the width of protrusion 448 at the level of ribs 448B, when protrusion 448 is not subjected to an external effort. Width W448 is chosen slightly larger than width W204, by an amount of less than 10 %. Thus, when ribs 448B are inserted within nick 204 upon mounting of rolling bearing assembly A within body B, ribs 448B are elastically deformed so that they converge and reduce the width of groove 448C. In other words, because of the respective widths of protrusion 448 and nick 204, protrusion 448 is elastically blocked within nick 204.

A multiconductor cable 45 is used to connect PCB 49 to a non represented electronic control unit adapted to receive the output signals of sensors 48A to 48D. The ends of some conductors 452 of cable 45 are connected to respective terminals 492 of PCB 49. Cable 45 is a shielded cable which includes an electrically conductive shield 454 embedded within a sheath 456 of cable 45. Shield 454 is connected to a conductor 458 whose end is connected to a plug 460 obtained by cutting and folding a metallic strip. Plug 460 has an elastically deformable tongue 462. The geometry of plug 460 is such that it can be inserted within volume V₄₄₈, while being connected to conductor 458 and with tongue 462 protruding within zone through opening 448D.

Thus, when support member 44 is mounted onto flange 442, conductor 458 and plug 460 elastically connect shield 454 to flange 442. When flange 442 is grounded, thanks to its mounting onto fixed ring 4, shield 454 is thus grounded, which enables it to reduce EMI noise in the signals conveyed by cable 45.

During manufacturing of sensing device 40, plug 460 is mounted at the end of conductor 458 and conductors 452 are respectively connected to terminals 492 before or after the respective pins of sensors 48A to 48E and the non represented sensor are connected to PCB 49. It is then possible to install holder 46 equipped with sensors 48A to 48E and PCB 49 within volume V₄₄₅, with PCB 49 lying in volume V₄₄₃ together with an end 45A of cable 45. Cable 45 goes through a slot 450 of support member 4. When installing the end 45A of cable 45 within volume V₄₄₃, plug 460 is inserted within volume V₄₄₈ of hollow protrusion 448 so that its tongue 462 protrudes within zone ¾₄.

It is then possible to close volume V₄₄₅ with a cover 43.

Then, support member 44 is mounted onto flange 42 and shield 454 is automatically set to the same electrical potential as flange 42.

When support member 44 is mounted onto flange 42, elastic tongue 462 exerts on the radial outer surface 425 of flange 42 an elastic biasing effort because elastic tongue 462 is slightly deformed towards volume V₄₄₈ when flange 42 is introduced within zone Z₄₄. This biasing effort induces an efficient electric contact between plug 460 and flange 42.

A rotation detection set according to the invention includes encoder washer 20 and sensing device 40.

According to a non represented embodiment of the invention, plug 460 can be omitted and the end of cable 458 can extend within volume V₄₄₈ and go through opening 448D in order to be engaged within a slot of flange 42 where it can be locked. Alternatively or in complement, the slot can be a stripping slot for stripping the sheath of conductor 458.

According to a non represented embodiment of the invention, support member 44 can be overmoulded over flange 42.

Even if it is particularly advantageous, holder 46 is optional. It is possible to install individually the sensors 48A to 48E within the housing V₄₄₅.

The invention has been represented with five sensors. However, it can be implemented with one or several sensors, whose number can be different of five.

The invention has been represented with the sensors 48A to 48D connected to cable 45 via PCB 49. Alternatively, in particular when only one sensor is used, the sensor of sensors can be connected directly to the cable.

In the second to sixth embodiments of the invention represented on figures 8 to 12, the same elements as in the first embodiment have the same references. Unless otherwise specified, the rolling bearing assembly A of these further embodiments is identical to the one of the first embodiment.

The rolling bearing assembly A of the second embodiment includes a rolling bearing 2 with a fixed outer ring 4 and a rotating inner ring 6 centered on a central axis X2. The main difference with respect to the first embodiment is that the protrusion 448 of the support member 44 has the same geometry along its longitudinal axis X448 which is parallel to axis X2.

The fixed body B adapted to accommodate rolling bearing assembly A has a central through hole 200 centered on an axis X200 which is superimposed with axis X2 in the mounted configuration of the rolling bearing assembly. The wall 202 of body B which surrounds hole 200 is symmetric with respect to axis 200. In other words, no nick or slot is provided in this wall. A ring 206 is held onto body B by three screws 208 and this ring is provided, on its inner radial edge with a nick 204 adapted to accommodate protrusion 448. Ring 206 surrounds support member 44 above wall 443. Nick 204 forms a recess for a part of protrusion 448 when bearing assembly A is mounted on fixed body B, which prevents bearing assembly A, and in particular its non represented sensors, to rotate around axes X2 and X200.

According to alternative embodiments of the invention, protrusion 448 can be formed on the radial inner wall 441 of support member 44, in case ball bearing 2 has a fixed inner ring and a rotating outer ring.

In the embodiment of figure 9, the support member 44 is circular and its radial outer surface 44B is provided with several ribs 448 which can operate with the edge of a non represented recess designed to accommodate rolling assembly A.

In the embodiment of figure 10, the support member 44 is also circular and its axial face 44C, which is opposite to the rolling bearing 2 and perpendicular to the central axis X2 of rolling bearing 2, is provided with three pins 448 which extend parallel to central axis X2. These pins 448 can cooperate with respective holes or recesses provided in a non represented fixed body which accommodate rolling bearing A.

In the embodiment of figure 1 1 , an approach similar to the one of the embodiment of figure 9 is followed with the ribs of the third embodiment replaced by four arms 448 which extend radially from the outer peripheral surface 44B of support member 44.

In the embodiment of figure 12, the circular support member 44 is provided with two opposed flat sections 448 on its radial outer surface 44B. These flat sections are adapted to cooperate with a ring similar to the ring 206 of the second embodiment in order to block the rolling bearing assembly A in rotation around the central axis X2 of the rolling bearing 2.

The invention has been represented with a rolling bearing. However, it is also usable with a plain bearing.

The invention has been represented with a fixed outer ring and a rotating inner ring.

However, it is also usable with a fixed inner ring and a rotating outer ring.

Claims

1. A rotation detection set comprising:

- an encoder washer (20) adapted to rotate around a rotation axis (X2, X20), - at least one sensor (48A-48D) adapted to detect a rotation parameter of said encoder washer,

- a support member (44) holding said sensor with respect to said rotation axis wherein said support member is provided with a relief (448) adapted to cooperate with a relief (204) of a fixed part (B) in order to immobilize said support member in rotation around said rotation axis (X2, X20).

2. Rotation detection set according to claim 1 , wherein said support member (44) is circular or arcuate and centered on said rotation axis (X2, X20) and wherein said relief (448) of said support member is provided on a radial outer or inner surface (442 ; 44B) of said support member (44).

3. Rotation detection set according to claim 1 , wherein said relief (448) of said support member (44) is provided on a front face (44C) of said support member which is perpendicular to said rotation axis (X2).

4. Rotation detection set according to one of the previous claims, wherein said support member (44) is made of moulded synthetic material and its relief (448) is integral with said support member.

5. Rotation detection device according to one of the previous claims, wherein said relief (448) of said support member protrudes from a face (442 ; 44B) of said support member (44).

6. Rotation detection device according to claim 5, wherein said relief (448) of said support member is at least partially (448A) elastically deformable.

7. Rotation detection device according to claim 6, wherein said relief (448) has at least two deformable ribs (448B) separated by a groove (448C), said ribs being adapted to be elastically pushed towards each other when they are received within a corresponding recess (204) of a fixed part (B).

8. Rotation detection device according to one of the previous claims, wherein:

- it includes an electrically conductive member (42),

- said support member (44) defines a housing (V₄₄₃) adapted to accommodate an end of a cable (45) connected, directly or via a printed circuit board (49), to said sensor (48A-48D),

- said support member has a hollow protrusion (448) whose internal volume (V₄₄₈) connects said housing to a zone (¾₄) defined by said support member and adapted to accommodate said electrically conductive member (42) and

- said relief (448) of said support member (44) is formed by said hollow protrusion.

9. Rotation detection device according to claim 8, wherein a part (448A) of said hollow protrusion (448) is elastically deformable.

10. A bearing assembly (A) comprising:

- a bearing (2), with a fixed ring (4) and a rotatable ring (6), and

- a rotation detection set (20, 40) according to one of the previous claims, said encoder washer (20) of said rotation detection set being fast in rotation with said rotatable ring (6) and said support member (44) being mounted on said fixed ring (4).

1 1 . An apparatus equipped with a bearing assembly (A) according to claim 10, said apparatus having a fixed part (B) provided with a relief (204) adapted to cooperate with said relief (448) of said support member (44) in order to immobilize said support member in rotation around an axis of rotation (X2, X20) of said rotatable ring (6) and said encoder washer (20).

12. Apparatus according to claim 1 1 , wherein said fixed part (B) surrounds an outer ring (4) of said bearing, said relief of said fixed part is a recess (204) provided on a radial inner edge (202) of said fixed part and said relief (448) of said support member (44) extends radially outwardly with respect to said outer ring.

13. Apparatus according to claim 1 1 , wherein said fixed part (B) surrounds at least one portion (44) of said rotation detection device, said relief of said fixed part is a recess (204) provided on a radial inner edge of said fixed part and said relief (448) of said support member extends radially outwardly with respect to said portion.