Abstract:
Bearing ( 1 ) with a built-in encoder ( 22 ) that comprises a fixed ring ( 2 ), a rotating ring ( 3 ) designed to be mounted on a rotating body ( 5 ), and rolling components ( 4 ) between them. A frame ( 13 ) forms, on the one hand, support for an annular encoder ( 22 ) to generate electromagnetic impulses and, on the other hand, a device for rigidly connecting the rotating body ( 5 ) and the rotating ring ( 3 ). The rotating ring ( 3 ) fits onto the connection device, which is designed to be inserted between the rotating body ( 5 ) and the rotating ring ( 3 ). Sensor ( 29 ) and steering system components may be added.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to the field of bearings with instruments and, more particularly, to bearings with a built-in encoder, where the encoder is an annular component that generates electromagnetic impulses. It also concerns an assembly an comprising such a bearing, and a sensor, where the sensor is a device to detect impulses generated by the encoder, and a vehicle steering system including such a bearing or assembly. 
     Such bearings are designed to permit, on the one hand, the rotation of a rotating body in relation to a fixed body and, on the other hand, the detection of angular position or speed or a function of such factors. When applied to a vehicle steering system, the system generally includes a steering shaft mounted to rotate in a steering column, as well as a rack and pinion gearbox, the column and the gearbox being fixed in rotation in relation to the chassis of the vehicle. The bearing or assembly may be inserted between the shaft and the column, or even between the shaft and the gearbox. 
     There already exist known bearings of the type that include a fixed ring, a rotating ring, and rolling elements between them, and in which an encoder is incorporated. In most embodiments, the bearing includes watertight means, the latter being used to support the encoder. For example, document FR 2,717,266, issued to the applicant, describes a device to detect the rotating speed of a roller bearing, which has an encoder component that forms part of the rotating part of the bearing. In that device, the encoder component is combined with the watertight gasket of the bearing. 
     For some applications, watertight means are not required, and the axial length of the bearing must be limited, the limitation on the size of the bearing thus constituting a constraint on a bulky design. Among such applications, one corresponds to a rack and pinion gearbox of a vehicle steering system. Document EP 856,720 describes an angular steering lock sensor for a steering system, the sensor including a magnet placed on the end of the steering shaft near which the stationary sensor is located. 
     In that case, the proposed structure, which permits an angular position to be read, is entirely different from those structures proposing integration of an encoder in a bearing. As a result, that embodiment has a number of disadvantages. On the one hand, it requires revision of the sensor support design, for example, the rack and pinion, in order to free the space needed to insert the sensor. On the other hand, the positioning of the sensor on the end of the shaft exposes it to attack from its surroundings, such as splattering from dust, gravel, or mud. 
     The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter. 
     SUMMARY OF THE INVENTION 
     In one aspect of the invention, this is accomplished by providing a bearing with a built-in encoder comprising a fixed ring, a rotating ring designed to be mounted on a rotating body, and rolling components between the fixed ring and the rotating ring. A frame forms, on the one hand, a support for an encoder and, on the other hand, a rigid connecting means between the rotating body and the rotating ring, the rotating ring fitting onto the connecting means, which is designed to be inserted between the rotating body and the rotating ring. The encoder is in the form of an annular means to generate electromagnetic impulses. 
     The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     FIG. 1 is a partial cross section of a bearing according to the invention; 
     FIG. 2 is a view similar to FIG. 1 of a mode of embodiment that is provided with a second frame; 
     FIG. 3 is a view similar to the above figures of another mode of embodiment, which is provided with a ring forming a support means for a sensor; 
     FIG. 4 is a view similar to FIG. 3, where the sensor is represented; 
     FIG. 5 is a view similar to FIG. 3, where the ring is provided with a lip that forms a ratchet means for the sensor; 
     FIG. 6 is a view similar to FIG. 5, where the sensor is represented; and 
     FIG. 7 is a partial cross section of a bearing according to the invention applied to a rack and pinion gearbox of a vehicle steering system. 
     Represented in the figures is lengthwise axis X that roughly constitutes the axis of rotation of the bearing. The terms “axial,” “lengthwise,” “front,” and “back” are defined in relation to that axis. A radial or crosswise direction is defined on a plane perpendicular to lengthwise axis X. An “inner” location is situated near axis X, while an “outer” location is situated at a distance from axis X. 
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, FIG. 1 illustrates bearing  1 , that includes fixed ring  2 , rotating ring  3 , and rolling elements  4  positioned between them. Bearing  1  is designed to be inserted between rotating body  5  and fixed body  6  to permit rotation of rotating body  5  in relation to fixed body  6 . 
     In the case of a shaft driven in rotation in relation to a casing, “shaft”  6  is referred to as the rotating body and “casing”  7  is referred to as the fixed body for greater convenience. Rotating ring  3  of the bearing is then inner ring  3 , and fixed ring  2  is outer ring  2 , this configuration being the one chosen for this description. However, the invention also applies in the inverse case, where the inner ring of the bearing is fixed and the outer ring turns. 
     In a conventional manner, inner ring  3  has boring  7  and two side faces, respectively front  8  and back  9 , while outer ring  2  has outer surface  10  and two side faces, front  11  and back  12  respectively. Inner ring  3  of the bearing is connected to rigid monoblock frame  13  comprising cylindrical axial section  14  and annular radial section  15  that projects outward, the cross section of this frame being generally L-shaped. Axial section  14  comprises outer face  16 , inner face  17 , and open axial end  18 , while radial section  15  comprises front wall  19  and back wall  20 , as well as open circumference  21 . The frame  13  is made preferably of a ferromagnetic material by tooling or stamping. 
     An annular encoder  22  is attached to front wall  19  of radial section  15  of frame  13 , and extends radially against the latter. Such an encoder  22  may be made of a synthetic material such as a polymer or elastomer charged with particles of ferrite. The encoder  22  may be attached to frame  13  by gluing or casting into a working mold. In one mode of embodiment, encoder  22  has a plurality of contiguous fields, each field having an inverted polarity in relation to the two fields contiguous to it. The embodiment of such an encoder  22  is itself known and will not be described in further detail herein. 
     Attaching inner ring  3  to frame  13  involves a step of forcing inner ring  3  of bearing  1  onto axial section  14  of the frame so that boring  7  of inner ring  3  cooperates with outer face  16  of axial section  14 . In order to prevent inner ring  3  from becoming disconnected from frame  13  during use, the attachment may further include a crimping step that consists of bending axial end  18  of frame  13  outward at several points, for example at three points 120° apart from one another. In other modes of embodiment, inner ring  3  and frame  13  may be glued, welded, ratcheted, or attached by comparable means. 
     When inner ring  3  is fitted onto axial section  14  of frame  13 , front face  8  of inner ring  3  rests against back wall  20  of radial section  15 . Axial end  18  of axial section  14  is then recessed in relation to back face  9  of inner ring  3 . There is thus a play J defined between axial end  18  of axial section  14  and rear face  9  of inner ring  3 . One advantage of this inserted attachment is that it permits rectification of the manufactured conicity of radial section  15  of frame  13 , and thereby ensures a roughly planar rotation of encoder  22  during use, and in all circumstances. 
     Bearing  1  is mounted on shaft  5  as follows: Frame  13  is fitted onto outer surface  23  of the shaft so that the inner face  17  of axial section  14  of frame  13  and outer surface  23  of shaft  5  cooperate, and that the back face  9  of inner ring  3  rests against shoulder  24  of shaft  5 . This support is possible due to the presence of play J between the axial end  18  of axial section  14  and the back face  9  of inner ring  3 . Stop ring  25 , such as a circlip, is then inserted in groove  26  provided in shaft  5 , said stop ring  25  being in contact with front wall  19  of radial section  15  of frame  13 , and keeping the latter in a fixed position on shaft  5 . 
     The assembly comprising shaft  5  and bearing  1  is then inserted in casing  6 , outer ring  2  fitting into receptacle  27  so as to roughly match it, front face  11  of outer ring  2  then resting against radial support face  28  of receptacle  27 . Finally, sensor  29  is attached to casing  6  by screws, ratcheting, or the like, reading component  30  of sensor  29  being positioned opposite encoder  22 . At least one, and for example a number of reading elements, are provided in reading component  30 , these elements being able to read the electromagnetic impulses emitted by encoder  22 . 
     Sensor  29  transmits the data emitted by this reading to signal processing means in order to deduce the angular position of encoder  22 , and from that, of inner ring  3  of bearing  1  in relation to outer ring  2 , or its angular speed, or even a function of the angular position or angular speed. The mode of embodiment just described may be applied alone or in combination with one of the variants to be described below. 
     In a mode of embodiment illustrated in FIGS. 3 to  6 , cylindrical ring  31  is provided, made of a rigid or semirigid material such as a metal or polymer, of which at least back end  32  is fitted onto outer ring  2 . The ring  31  includes front end  33  designed to rest against sensor  29  when the latter is attached to casing  6 . This support permits reading component  30  of sensor  29  to be kept at a predetermined desired distance from encoder  22 . Such distance is referred to as the gap. In addition, ring  31  may include, near its extreme front section  33 , lip  34  that projects radially outward from ring  31 , this lip  34  matching with claw  35  provided in sensor  29 , and engaging with it. Thus, when sensor  29  is mounted on casing  6 , sensor  29  is ratcheted to ring  31  by means of lip  34  and claw  35 , which permits the gap to remain constant during use. 
     In another mode of embodiment illustrated in FIG. 2, second frame  36  is provided connected to outer ring  2  of bearing  1 , comprising cylindrical axial section  37  and annular radial section  38  that projects inward. Axial section  37  includes outer face  39 , inner face  40 , and open axial end  41 , while the radial section includes front wall  42  and back wall  43 , as well as open circumference  44 . This second frame  36  may be fitted onto receptacle  27  of casing  6 , the shape of receptacle  27  matching second frame  36 , front wall  42  of radial section  38  thus resting against support face  28  of receptacle  27 . The attachment of second frame  36  to outer ring  2  of the bearing includes a step of fitting second frame  36  onto outer ring  2  so that outer surface  10  of outer ring  2  engages the inner surface  40  of axial section  37 . Once this attachment is made, outer wall  43  of radial section  38  of frame  36  rests against front face  11  of outer ring  2  of bearing  1 . 
     In a manner similar to first frame  13 , in order to prevent outer ring  2  from becoming disconnected from frame  36  during use, the attachment may include a crimping step that consists of bending axial end  41  of the frame inward at a plurality of points, for example at three points 120° apart from one another. Instead of or in addition to a crimping step, gluing or welding of second frame  36  to outer ring  2  may be used. In this variant, sensor  29  is provided to be attached by screws, ratcheting, or the like to second frame  36 , for example against front wall  42  of radial section  38 , so that reading component  30  is positioned opposite encoder  22  with a gap between them. 
     Although the above description has been made on the basis of bearing  1  with inner rotating ring  3  and outer fixed ring  2 , the invention also applies to a bearing  1  which the inner ring is fixed and the outer ring turns. In that case, encoder  22  may be attached by casting in a working mold or the like to second frame  36  in the manner described above, while sensor  29  may be attached to first frame  13  as described above, or directly on the fixed body. 
     The present invention may further be provided with watertight means or means to support watertight means. The rotating ring of the bearing may be connected to the frame by fitting it onto it by force and/or by crimping, ratcheting, gluing, welding, or the like. The frame may be made of a ferromagnetic material; and, for example, it may be made by bending sheet metal at a right angle. If desired, one axial dimension of the axial section of the frame may be roughly equal to one axial dimension of the rotating ring of the bearing, while one radial dimension of the radial section of the frame is roughly greater than one radial dimension of the rotating ring. 
     According to one construction, the encoder may be an annular piece made of a synthetic material charged with particles of ferrite, and composed of a plurality of contiguous fields with inverted magnetic direction of a given field in relation to the two fields contiguous to it. The encoder may be attached to the frame by casting it into a working mold. For example, the encoder may extend over one face of the radial section of the frame, opposite the rotating ring. 
     The bearing may include integrated means to position a sensor, which is present in the form of a device to detect the impulses generated by the encoder, such means being carried on the fixed ring. For example, the means to position the sensor may be in the form of a ring fitted onto the fixed ring of the bearing. Such means to position the sensor may include sensor support means and/or sensor ratcheting means. The bearing may also include a sensor connected to the fixed ring by means of a second frame that constitutes, on the one hand, means to support the sensor and, on the other, a rigid connection means between the fixed ring and the fixed body. 
     The sensor includes at least one reading element, for example a plurality of reading elements in a line, placed opposite the encoder, chosen from among the group comprising Hall-effect probes and magnetic resistances, one application of the invention is a vehicle steering system that comprises a steering shaft, steering column, and possibly a rack and pinion gearbox, and a bearing or an assembly as described above inserted between the steering shaft and the steering column, or between the steering shaft and the gearbox.