Abstract:
Instrumented rolling bearing device for measuring the rotation parameters of the bearing, including a rotating race, a non-rotating race, at least one row of rolling elements placed between the non-rotating and rotating races, a rotating coder and a pliable non-rotating electronic circuit board comprising at least one sensor and at least one flat folded zone supporting the said sensor and pressing on a rigid reference surface forming part of a sensor block, at least one sensor being in the form of a spot-type detector cell.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to the field of instrumented rolling bearings furnished with a device for detecting the rotation parameters of the rolling bearing such as the angular position, the angular speed, or the angular acceleration of the rotating portion. 
         [0003]    2. Description of the Relevant Art 
         [0004]    Such rolling bearings usually use a coder ring fixed to the rotating portion, for example a multipolar ring and one or more sensors placed axially or radially opposite the active portion of the coder ring, for example Hall effect cells. The sensors are fixed to a rigid printed circuit board usually perpendicular to the axis of rotation of the rolling bearing. If a minimum axial space requirement of the rolling bearing is desired while obtaining a stable and repetitive output signal, it is possible to make use of the great radial rigidity of the rolling bearing and provide a radial air gap between the coder and the sensor, see document FR-A-2 882 139. 
         [0005]    In this case, certain technical points are difficult. The sensor must be positioned radially with great precision relative to the coder, which is difficult and assumes that the sensor rests on a reference surface itself positioned with precision relative to the coder. It is often necessary to have recourse to resin attachment of the sensor on its support to hold it in the appropriate position, which is a costly operation. Furthermore, the connection lugs of the sensor are placed perpendicular to the rigid printed circuit board and traverse the board through small holes to emerge on the other side where the lugs are soldered to the circuit, the protruding portion of the lugs then being cut off. Here again, these operations are costly. 
         [0006]    Document FR 2 655 735 describes a sensor including a conductor, shaped in meanders on a printed circuit, bonded to a stator. The conductor consists of a strand sandwiched between two insulating films. This type of sensor of the inductive type does not provide a sufficiently powerful and precise signal to suit all industrial applications. 
       SUMMARY OF THE INVENTION 
       [0007]    In an embodiment, a speed sensor device supplies a signal that is precise and stable over time in a very small axial space requirement and for a reasonable cost. 
         [0008]    According to one embodiment, an instrumented rolling bearing device for measuring the rotation parameters of the bearing includes a rotating race, a non-rotating race, at least one row of rolling elements placed between the non-rotating and rotating races, a rotating coder and a non-rotating electronic circuit board supporting at least one sensor. The electronic circuit board is pliable and includes at least one flat folded zone supporting the said sensor and pressing on a rigid reference surface forming part of a sensor block, at least one sensor being in the form of a spot-type detector cell. 
         [0009]    The fact that the electronic circuit board is pliable makes it possible to precisely adjust the zone of the board supporting the sensor on the reference surface, hence a precise positioning of the sensor. In addition, the arrangement of the sensor on the flat portion of the board makes it possible to obtain a precise and sound positioning. This provides a sensor supplying a signal that is precise and stable over time. 
         [0010]    “Spot-type detector cell” here means a cell occupying a limited angular sector. In other words, the cell extends angularly in a limited manner in the circumferential direction about the axis of rotation of the rolling bearing. The sensor therefore includes two distinct ends separated by a certain distance in the circumferential direction. 
         [0011]    The electronic circuit board is formed so as to obtain locally a flat portion that forms an angle with the adjacent portion of the board and on which at least one sensor is mounted. 
         [0012]    In one embodiment, the electronic circuit board also includes electronic components for processing the signal transmitted by the sensor or sensors. The electronic components and the sensor or sensors may be placed on one and the same face of the electronic circuit board. Alternatively, the electronic components, on the one hand, and the sensor or sensors, on the other hand, are placed on opposite faces of the electronic circuit board. 
         [0013]    In one embodiment, the electronic circuit board also includes a connector placed on one and the same face as the sensor or sensors or on the opposite face. 
         [0014]    In one embodiment, the zone supporting the sensor is fixed to the reference surface by bonding. 
         [0015]    In one embodiment, the zone supporting the sensor is fixed to the reference surface by mechanical retention. The pliable zone supporting the sensor may be fixed to the reference surface by a clip. The clip may be in the form of a piece of metal sheet curved in the shape of a C or in the shape of an Ω. 
         [0016]    In one embodiment, the device includes a sensor block fixed to the non-rotating race and supporting the electronic circuit board. The sensor block may include a cap and an intermediate support furnished with at least one reference surface for the sensor or sensors. The cap may be furnished with at least one element for positioning and retention of the intermediate support and of the electronic circuit board. 
         [0017]    The sensor block may be furnished with at least one reference surface for the sensor or sensors and with at least one element for positioning and retention of the electronic circuit board. 
         [0018]    In one embodiment, the electronic circuit board is, after installation in the sensor block, in the form of a radial ring furnished with at least one axial lug forming a zone of support for the sensor. Alternatively, the electronic circuit board may be, after installation in the sensor block, in the form of an axial ring that is open or has joined ends. “Axial ring” means a ring having an axial dimension greater than its radial dimension. The radial dimension may correspond to the thickness of the electronic circuit board and the axial dimension to its width. The electronic circuit board may include bent portions and straight portions, the straight portions being furnished with reinforcements. The reinforcements may form enlarged thicknesses. The device may include at least two rows of sensors placed in distinct radial planes. It is therefore possible to assign one row of sensors to a first coder and the other row of sensors to a second coder for the purpose of carrying out two distinct detections, for example on two rolling bearings. 
         [0019]    The method of manufacturing an instrumented rolling bearing device for measuring the rotation parameters includes a rotating race, a non-rotating race, a row of rolling elements placed between the rotating and non-rotating races, a rotating coder and an electronic circuit board including at least one sensor. The said at least one sensor is fixed to the electronic circuit board, the electronic circuit board is formed by folding and the said electronic circuit board is installed in a sensor block, a flat folded zone of the electronic circuit board supporting a sensor pressing on a rigid reference surface of the sensor block. The sensor may be fixed to the electronic circuit board by soldering. 
         [0020]    In one embodiment, the electronic circuit board is fixed to the sensor block by material spinning of a portion of the sensor block. 
         [0021]    In one embodiment, the said at least one sensor is fixed to a single face of the electronic circuit board. 
         [0022]    In one embodiment, the zone of the electronic circuit board supporting the sensor is bonded to the reference surface. 
         [0023]    In another embodiment, the zone of the electronic circuit board supporting the sensor is clipped to the reference surface. 
         [0024]    The sensor is capable of supplying a signal that is precise, reliable and stable over time and of doing so with a reduced axial space requirement and a low cost. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The present invention will be better understood on reading the detailed description of a particular embodiment, taken as an example that is in no way limiting, and illustrated by the appended drawings in which: 
           [0026]      FIG. 1  is a front view in elevation of an electronic circuit board according to one embodiment; 
           [0027]      FIG. 2  is a side view in elevation of the electronic circuit board of  FIG. 1 ; 
           [0028]      FIG. 3  is a rear view in elevation of the electronic circuit board of  FIG. 1 ; 
           [0029]      FIG. 4  is an exploded view in perspective of a sensor block furnished with an electronic circuit board; 
           [0030]      FIG. 5  is a view in perspective in the installed state of the sensor block of  FIG. 4 ; 
           [0031]      FIG. 6  is a view in axial section of a rolling bearing fitted with the sensor block of  FIG. 5 ; 
           [0032]      FIGS. 7 to 11  are views corresponding respectively to  FIGS. 1 to 5  of an electronic circuit board and a sensor block according to another embodiment; 
           [0033]      FIGS. 12 and 13  are views corresponding respectively to  FIGS. 4 and 5  of a sensor block according to another embodiment; 
           [0034]      FIG. 14  is a view in perspective of the clip of the sensor block of  FIGS. 12 and 13 ; 
           [0035]      FIG. 15  is a front flattened view of an electronic circuit board according to another embodiment; 
           [0036]      FIG. 16  is a side view in elevation of the electronic circuit board of  FIG. 15 ; 
           [0037]      FIG. 17  is a view in perspective of the formed electronic circuit board of  FIG. 15 ; 
           [0038]      FIG. 18  is a view in perspective of a sensor block furnished with the electronic circuit board of  FIG. 17 ; 
           [0039]      FIG. 19  is a view in axial section of a rolling bearing fitted with the sensor block of  FIG. 18 ; and 
           [0040]      FIGS. 20 to 24  are views corresponding respectively to  FIGS. 15 to 19  according to another embodiment. 
       
    
    
       [0041]    While the invention may be susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. The drawings may not be to scale. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but to the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0042]    Generally in what follows, the reference numbers of similar elements have been retained from one figure to the next. 
         [0043]    As illustrated in  FIGS. 1 to 3 , the electronic circuit board  1  includes a printed circuit  2  of the flexible and pliable type, for example including a polyamide-based substrate and one or more conducting layers. The printed circuit  2  has the general shape of an annular disc furnished with three tabs  3  extending radially towards the inside of the disc, cut-outs  4  being arranged between two sides of a tab  3  and the rest of the annular disc so that the rectangular-shaped tab  3  is connected only by one side to the annular disc  4 , particularly the side opposite to the centre of the annular disc  4 . The cut-outs  5  are preferably parallel with one another for each tab  3 . 
         [0044]    The printed circuit  2  supports electronic components  6  placed on the annular disc  4 , for example by automated mounting with surface fixing. Three through-holes  7  are arranged in the annular disc  4  and are evenly distributed circumferentially while alternating with the tabs  3 . The electronic circuit board  1  also includes a connector  8  protruding radially outwards in line with a tab  3 . For the purpose of a particularly robust attachment, the connector  8  may be fixed by lugs  9  protruding into holes  10  of the printed circuit  2 , see  FIGS. 2 and 3 . The electronic circuit board  1  also includes three sensors  11 , each fixed to a tab  3 , for example by surface-mounting. The sensors  11  may be of the magneto-sensitive type, for example a Hall effect cell. The sensors  11 , shown in  FIG. 3 , are mounted on the face of the printed circuit  2  opposite to the face supporting the electronic components  6 . 
         [0045]    In  FIGS. 1 to 3 , the electronic circuit board  1  is shown in an intermediate state, the tabs  3  being directed radially inwards. The tabs  3  are then folded to have a flat axial shape that can be seen in  FIGS. 4 and 5 . The folding of the tabs  3 , from the original radial position to the final axial position may be carried out by a machine furnished with a tool, which may or may not be a heating tool, provided for this purpose. The sensors  11  face inwards. 
         [0046]    The sensor block that can be seen in  FIGS. 4 and 5  includes an intermediate support  12  and a cap  13  able to interact with the electronic circuit board  1  for the purpose of an angular indexation of these two elements. The intermediate support  12  has the shape of a part, for example made of synthetic material such as a polyamide, of generally annular shape corresponding to that of the disc  4 . The intermediate support  12  is furnished with three pairs of lugs  14  extending axially. The lugs  14  of a pair of lugs are situated relative to one another at a distance greater than the width of the sensor  11  and of its attachment pins. The axial length of the lugs  14  is substantially equal to that of the tabs  3 . 
         [0047]    Arranged in the intermediate support  12  are three through-holes  15  evenly distributed circumferentially and alternating with the pairs of lugs  14  with a position and a diameter corresponding to the holes  7  of the electronic circuit board  1 . Notches  16  are also arranged in the intermediate support  12  radially inside the lugs  14 . The notches  16  correspond to the notches delimited by the cut-outs  5  after the tabs  3  are folded. 
         [0048]    During the assembly of the electronic circuit board  1  and of the intermediate support  12 , the face of the electronic circuit board that can be seen in  FIG. 3 , opposite to that supporting the electronic components  6 , comes into contact with a radial face of the intermediate support  12 . Each pair of lugs  14  passes on either side of a sensor  11  and comes to form a flat rigid reference surface  14   a  for the tabs  3  supporting the sensors  11 . The lugs  14  thereby give the tabs  3  a satisfactory rigidity. 
         [0049]    The cap  13  includes an outer axial wall  17  furnished with a notch  18  for the connector  8  to pass through, a radial wall  19  extending inwards from an end of the axial wall  17  opposite to the notch  18 , and an axial wall  20  of small diameter extending from the inside of the radial wall  19  in the same direction as the axial wall  17 . The cap  13  also includes three axial posts  21  supported by the radial wall  19  on the side of the axial walls  17  and  20 , and evenly distributed circumferentially. 
         [0050]    During assembly, the intermediate support  12  and the electronic circuit board  1  are housed in the cap  13  with the posts  21  passing through the holes  15  of the support  12  and through the holes  7  of the electronic circuit board  1 . The connector  8  protrudes radially outwards through the notch  18 . The axial walls  17  and  20  of the cap  13  have an axial length that is greater than the thickness of the annular body of the support  12  and of the annular disc  4  of the electronic circuit board  1 . The lugs  14  of the support  12 , the tabs  3  and the sensors  11  protrude axially relative to the inner axial wall  20 . 
         [0051]    The electronic circuit board  1  and the sensor block formed by the support  12  and the cap  13  may then be fixedly attached in a particularly robust manner by deforming the posts  21  in the manner of rivets, for example by hot deforming. This causes the end of the posts  21  to widen to form a rivet head  22 , see  FIG. 6 . 
         [0052]    The sensor block and the electronic circuit board  1  may then be installed in a cup  23  of generally annular shape including an axial wall  24  of large diameter furnished with a bore into which the outer surface of the large diameter axial wall  17  of the cap  13  is fitted, a radial wall  25  extending inwards from the axial wall  24  and an axial rim  26  extending away from the axial wall  24  from the small diameter end of the radial wall  25 , see  FIG. 6 . The cup  23  may be furnished with a notch to allow the connector  8  to pass through. 
         [0053]    The assembly thus formed may be mounted onto a rolling bearing  27 . The rolling bearing  27  includes an outer race  28 , an inner race  29 , a row of rolling elements  30  placed between the outer race  28  and inner race  29 , a cage  31  for keeping the rolling elements  30  evenly spaced circumferentially and a sealing flange  32  fixed to the outer race  28  and forming a narrow passageway with the inner race  29 . The outer race  28  may be symmetrical relative to a radial plane and have a transverse radial surface  28   a  on the side of the sensor block, a transverse radial surface  28   b  on the side of the sealing flange  32 , an outer surface  28   c  and a bore  28   d  from which is arranged a raceway on the rolling elements  30 . The outer race  33  includes two grooves  33   a  and  33   b  arranged from the bore  28   d  and close to the transverse surfaces  28   a  and  28   b . One groove  33   b  of the two grooves is used for fixing the flange  32 . The axial rim  26  of the cup  23  is fitted into the rim of the groove  33   b , the radial portion  25  coming into contact with the transverse surface  28   a  of the outer race  28 . 
         [0054]    The inner race  29  supports a coder  34  including an active portion  35  and a support  36  fitted to an outer surface of the inner race  29 . The support  36  may be in the form of an annular cup made of metal sheet. The active portion  35  may be overmoulded onto the outside of the support  36  and have an axial outer surface coming opposite the sensors  11  with a radial air gap. 
         [0055]    In addition, to increase the rigidity of the tabs  3 , it is possible to provide an enlarged thickness  37  increasing the thickness of the printed circuit  2  at the tabs  3  and locally stiffen the printed circuit in order to give it at the tabs a flat shape that it will tend to retain. The stiffening layer may consist, for example, of a layer of epoxy resin filled with glass fibres applied locally to the flexible substrate. The enlarged thickness  37  is placed on the side of the tabs  3  opposite to the sensors  11 . 
         [0056]    An instrumented rolling bearing is thus formed with a radial air gap and with a small axial space requirement because of the sensor  11  partly protruding into the space between the outer race  28  and inner race  29  and thanks to the fact that the electronic components  6  are housed in the sensor block in the axial space requirement of the sensors  11 . In the same manner as the other electronic components, the sensors may be fixed to the printed circuit  2  by soldering, prior to the folding of the tabs, the said circuit then being flat. The method of installing the sensors and other electronic components may easily be automated with the aid of a robot by using the “Pick-and-place” technique. 
         [0057]    In the position illustrated in  FIG. 6 , the sensors  11  are directly opposite the coder  34 . It is possible in this way to prevent immersing the sensors  11  in a resin or a synthetic material, thereby saving time and labour and gaining a better signal supplied by the sensors  11 . 
         [0058]    In the embodiment illustrated in  FIGS. 7 to 11 , the electronic circuit board  1  is similar to that of the preceding embodiment except that the tabs  3  protrude radially outwards from the annular disc  4  before folding. The presence of notches is not necessary. The sensors  11  and the electronic components  6  may be fixed to the same face of the printed circuit  2 , see  FIG. 9 . The same applies to the connector  8 . 
         [0059]    From the intermediate state illustrated in  FIGS. 7 to 9 , the tabs  3  are folded at 90° and thereby become parallel to the axis of the annular disc  4 . They are folded towards the side supporting the electronic components  6 . After folding, the tabs have a flat shape. 
         [0060]    The electronic circuit board  1  may then be installed in the cap  13  that can be seen in  FIGS. 10 and 11 . The presence of an intermediate support is not indispensable. The cap  13  is similar to that illustrated previously except that the bore of the outer axial wall  17  is furnished with three protuberances  38  directed radially inwards and evenly spaced circumferentially while alternating with the posts  21 . Each protuberance  38  has a radial thickness that is generally less than half the radial dimension of the radial wall  19  of the cap  13  and extends axially over all or some of the axial length of the axial wall  17 . Each protuberance  38  has a reference surface  38   a  parallel to the axis of the cap  13  and of the electronic circuit board  1 . The reference surfaces  38   a  may be normal to a radial straight line. 
         [0061]    As can be seen in  FIG. 10 , the electronic circuit board  1  may be brought into the cap  13  by a simple axial movement. The connector goes into the notch  18 . Each tab  3  is pressing against a flat reference surface  38   a . The posts  21  go into the holes  7  to culminate in the state illustrated in  FIG. 11 . The posts  21  may then be deformed for the final attachment of the electronic circuit board in the cap  13 . The tabs  3  may be held against the reference surfaces  38   a  by bonding, for example by placing a drop of adhesive on each reference surface  38   a  just before inserting the electronic circuit board  1  into the cap  13 . 
         [0062]    In the embodiment illustrated in  FIGS. 12 to 14 , the electronic circuit board  1 , the intermediate support  12  and the cap  13  are identical to those of the first embodiment of  FIGS. 1 to 6 . Additionally, the flat tabs  3  are fixed to the lugs  14  of the intermediate support  12  by clips  39 , see  FIG. 14 . A clip  39  is provided to lightly squeeze a tab  3  against the flat reference surfaces  14   a  of a pair of lugs  14 . Folding a metal sheet blank may make the clips  39 . A clip  39  is symmetrical relative to a central plane. 
         [0063]    A clip  39  includes a rectangular body  39   a  from opposite ends of which two symmetrical wings  39   b  extend perpendicular to the body  39   a . From the ends of the wings  39   b  away from the body  39   a , two rims  39   c  extend parallel to the body  39   a  and turn inwards. The clips  39  may be pre-placed on the electronic circuit board  1  after the tabs  3  have been folded as illustrated in  FIG. 13  or else be mounted after the electronic circuit board  1 , the intermediate support  12  and the cap  13  have been assembled. The body  39   a  is in contact with the face of the tab  3  opposite to the sensor  11 . The wings  39   b  surround the ends of the tabs  3  and an edge of the lugs  14 . The rims  39   c  facing one another are pressing on an axial face of the lugs  14  opposite the reference surfaces  14   a . A clip  39  lightly pinches the tab  3  of the printed circuit  2  against the reference surface  14   a  of the lugs  14 , a tab  3  and a lug  14  being clipped between a rim  39   c  and the body  39   a.    
         [0064]    In the embodiment illustrated in  FIGS. 15 to 19 , the printed circuit  2  is in the form of a flat elongated rectangular strip in the intermediate state illustrated more particularly in  FIGS. 15 and 16 . The printed circuit  2  includes flat sections  40  supporting the electronic components  6 , flat sections  41  each supporting a sensor  11  and if necessary electronic components  6 , a flat section  42  supporting the connector  8  and, as appropriate, electronic components  6  and sections  43  with no electronic components or sensors. The sections  43  may naturally be furnished with printed conductor tracks linking the other sections. The sections alternate in the sense that a section  40 ,  41  or  42  is placed between two sections  43 . The sections  40 ,  41  and  42  are reinforced by an enlarged thickness  44  similar to the reinforcement  37  illustrated in  FIG. 6 . 
         [0065]    The sensors  11  and the electronic components  6  are placed on one face of the printed circuit  2 . The connector  8  and the reinforcements  44  are placed on the opposite face. 
         [0066]    The electronic circuit board  1  is then formed in order to give it the appearance illustrated in  FIG. 17 . The sections  43  with no components or sensors are folded with a relatively slight curvature and the sections  40  to  42  remain straight, particularly thanks to the reinforcement  44 . This therefore gives a general shape of an open hexagon with the sensors  11  evenly distributed circumferentially substantially at 120 degrees. The electronic circuit  1  includes five bent sections  43  separating six straight sections, three sections  41  supporting a sensor  11 , two sections  40  supporting electronic components  6  and one section  42  supporting the connector  8 . 
         [0067]    The electronic circuit  1  is then placed in a cap  13  of the type illustrated in  FIG. 18 , having the shape of a casing including a ring  45  provided with a circular outer surface  46  and an inner surface  47  matching the shape of the electronic circuit board  1  in its state illustrated in  FIG. 17 , in other words, in the shape of a hexagon with rounded corners, so that the reinforcements  44  placed on the outside of the sections  40 ,  41  and  42  are in contact with the inner surface  47  thereby providing an excellent positioning of the sensors  11  in the cap  13 . The inner surface  47  includes straight portions  47   a  in contact with the reinforcements  44  and rounded portions  47   b  that can remain at a short distance from the bent sections  43 . The reinforcements  44  may be fixed by bonding onto the portions  47   a , which form the reference surfaces. The ring  46  includes two radial transverse surfaces of which the surface  49  can be seen in  FIG. 18 . A notch may be arranged to allow the connector  8  to protrude radially outwards from the ring  46 . 
         [0068]    As illustrated in  FIG. 19 , the cap  13  also includes a radial wall  50  closing off an axial end of the ring  45  and placed on the side opposite to the cup  23  fixed in the groove  33   a  of the rolling bearing  27 . The sensors  11  are placed on the inner face of the electronic circuit board  1 , outside the active portion  35  of the coder  34  with a radial air gap as in the preceding embodiments. The sensors  11  are supported by straight sections  41  of the electronic circuit board  1  furnished with reinforcements  44  in contact with the straight surface  47   a  formed in the inner surface of the ring  47  of the cap  13 , thereby forming reference surfaces. The reinforcement  44  may be bonded to the flat reference surfaces  47   a  in order to stabilize the positioning of the sensors  11 . 
         [0069]    In the embodiment illustrated in  FIGS. 20 to 24 , the electronic circuit  1  is in a general form similar to that of the preceding embodiments, with a markedly increased, for example doubled, width, as can be seen in  FIG. 20 , in comparison with  FIG. 15 . The printed circuit  2  includes five sections  43  with no components and six flat sections  40  each supporting a sensor  11  and electronic components  6 . One of the sections  40  also supports the connector  8 . The sensors  11  are placed in two rows of three sensors  11  in an alternating manner, each portion  40  supporting a sensor  11 . After the electronic circuit board  1  has been formed, see  FIG. 22 , the sensors  11  are distributed in two groups of three, each group being placed in one and the same radial plane, the two radial planes being offset axially relative to one another. Once formed, the electronic circuit board  1  is placed in the cap  13  having an annular shape similar to that of  FIG. 18  but with a greater axial width to suit the increased axial width of the electronic circuit board of this embodiment. 
         [0070]    As can be seen in  FIG. 24 , the cap  13 , with no radial wall, includes a window  48  allowing the connector  8  to protrude outwards. The cap  13  is designed to interact with two cups  23 , each placed at an axial end of the cap  13 . Each axial cup  23  is fixed to a rolling bearing  27 . Therefore, the rolling bearing  27  whose outer races  28  are fixedly attached in rotation may be instrumented, each inner race  29  being furnished with a coder  34 , each coder  34  supplying a magnetic signal to a group of sensors  11  dedicated to the said coder  34 . In the embodiment shown, each group of coders  11  includes three coders  11 . This gives an assembly of two instrumented rolling bearings with a small axial and radial space requirement and which is able to be manufactured at reasonable cost. 
         [0071]    It is therefore easy to install all the electronic components and sensors on a printed circuit in an automated and economic manner, the electronic circuit board thus formed then being installed in a sensor block. 
         [0072]    Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as examples of embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims.