Abstract:
The rotation angle and torsion angle sensor detects both the rotational position of a shaft and a torque applied to the shaft torque. The shaft a first shaft part and a second shaft part, which are interconnected by a torsion bar. A sensor disc is coupled via a rigid circumferentially and axially flexible membrane with the first shaft part. The sensor disc is coupled to a drive wheel via a coupling device, in such a way that the sensor disc is displaced in the axial direction upon relative rotation of the two shaft parts against each other, wherein the membrane bends in the axial direction.

Description:
FIELD OF INVENTION 
       [0001]    The invention relates to a rotation angle and torsion angle sensor. A preferred application of the embodiments of the invention is the steering of motor vehicles, in which not only the angle of rotation of a steering shaft is to be measured, but also the force exerted on the steering shaft forces which affect the torque. This torque can be measured as a torsion shaft angle of a torsion shaft which is arranged between two sections of the steering shaft torsion bar. The other parameters of the torsion bar are known. 
       BACKGROUND 
       [0002]    The DE 3802684 A1 discloses a torque sensor for electric power steering with a torsion bar whose two ends are connected to the cylindrical sleeves, each of which surrounds about half of the torsion bar. Both sleeves carry at their mutually facing ends, each an annular neck, which is connected by flexible webs with a hollow cylindrical ring. Upon relative rotation of the two ends of the torsion bar, the latter ring is displaced in the axial direction, which is detected by the hollow-cylindrical ring associated sensor coils. 
         [0003]    More generally speaking, a relative rotation of two portions of a shaft by means of a mechanical connection will be converted into an axial linear motion. 
         [0004]    This general principle is also known in the following publications: 
         [0005]    EP 2108932 A2 (U.S. 8,109,156 B2), in which an link guide is used, 
         [0006]    U.S. Pat. No. 5,115,685 A, which shows a resiliently elastic element with deformable webs, 
         [0007]    U.S. Pat. No. 2,260,036 with a link guide and coupling of a sensor element via coil springs, 
         [0008]    U.S. Pat. No. 5,165,288, where a lever linkage moves a transmitter ring, 
         [0009]    U.S. Pat. No. 4,907,461, wherein two annular discs are coupled together by springs, 
         [0010]    U.S. Pat. No. 4,809,557 and U.S. Pat. No. 6,370,968, where again link guides be employed and finally 
         [0011]    U.S. Pat. No. 6,854,322 and U.S. Pat. No. 5,353,684. 
         [0012]    For the simultaneous measurement of torsion and rotation angle, it is known from EP 1426750 1 and U.S. Pat. No. 7,258,027 B2 to use gears, magnets and magnetic sensors. 
         [0013]    The above-described sensors for simultaneous measurement of torsion and rotation angle are mechanically very complex. 
       SUMMARY 
       [0014]    One object of the invention is therefore to simplify the above-mentioned torsional and rotational angle sensor, and still maintain accurate measurement results. 
         [0015]    For achieving this object, the invention proposes an angle of rotation and torsion angle sensor including a first shaft part and a second shaft part connected to each other via a torsion bar; a driven wheel connected to the second shaft part, the driven wheel engaged with a first sensor wheel and a second sensor wheel, the first sensor wheel and the second sensor wheel associated with a first sensor and a second sensor for detecting the rotational position; and a membrane circumferentially rigid and flexible in the axial direction, the membrane having a first terminal and a second terminal, the first terminal coupled directly or indirectly to the first shaft part and the second terminal connected with a sensor disc via a connecting device; wherein the sensor disc is coupled to the driven wheel via coupling elements, such that a relative rotation of the first shaft part and the second shaft part against one another causes an axial displacement of the sensor disc; and wherein a third sensor detects the axial position of the sensor disc. 
         [0016]    The basic idea of the invention is the use of an annular membrane which is flexible in the circumferential direction as far as possible, and rigid in the axial direction. This membrane is directly or indirectly coupled to a first shaft part and having a sensor disc which is in turn coupled with a further annular disc. The latter annular disc is coupled to a second shaft portion. By this coupling, the sensor disc is axially displaceable. The axial position of the sensor wheel is detected by a sensor. In addition to the shaft part connected to the second annular disk, the rotation position of the corresponding shaft part is sensed by the sensor wheels whose rotating position is detected by sensors. The annular disc and the sensor wheels are engaged together, with meshing gears. 
         [0017]    According to one embodiment of the invention, the coupling elements are rod-like elements which are articulated between the wheel sensor and the drive wheel, and which are non-stretchable in their longitudinal direction. 
         [0018]    The coupling elements can also be a flexible or pliable, but non-extensible material strips. The elements are disposed between the sensor disc and the drive wheel. 
         [0019]    According to one embodiment of the invention, the coupling elements are formed by a mechanical forced guide in the form of a threaded or a link guide. 
         [0020]    According to a further variant, the coupling elements are formed by levers that are mounted on the drive wheel via a pivot, one end of the lever via a hinge to a connection of the membrane and another end of the lever via a further hinge, connected directly or indirectly to the sensor disc. 
         [0021]    Preferably, these levers are arranged in two perpendicular legs which are rigidly connected to each other. 
         [0022]    According to an embodiment of the invention, a connection of the membrane is connected by a funnel-like element with the sensor disc. The sensor disc can be connected through a link ring with the funnel-like element. 
         [0023]    According to a further embodiment of the invention the membrane is connected to a drive wheel, which is in rotational engagement with a driven wheel, which is connected to the first shaft part. 
         [0024]    According to one embodiment of the invention, a connector of the membrane is connected to an axially displaceable sleeve, which is connected to the sensor disc and a magnetic pen. An additional sensor is then associated with the magnetic pen. 
         [0025]    According to a further embodiment of the invention, a connector of the membrane is joined with a threaded sleeve and a magnetic pin, wherein the threaded sleeve is connected to a threaded pin, which is fixedly connected with the sensor wheel. 
         [0026]    According to a further variant of the invention, the membrane is rigid in the circumferential direction and in the axial direction and is coupled indirectly with the first shaft part through a driven wheel and a first shaft part, which is connected to the drive wheel. The driven wheel is axially displaceable and coupled with the first sensor wheel that is displaceable in relative rotation between the two shaft parts. The magnetic pin is fixedly connected to the driven wheel, and moves with it. The magnetic pin is associated again with the fixed further sensor, detecting the axial position of the magnetic pin. 
         [0027]    For the coupling between the driven wheel and the sensor wheel, the variants described above can be used. 
         [0028]    In the following, the invention is explained in detail by way of exemplary embodiments in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         [0029]      FIG. 1  a schematic, partly cutaway perspective view of a rotation angle and torsional angle sensor according to a first embodiment of the invention; 
           [0030]      FIG. 2  a sensor according to a second embodiment of the invention; 
           [0031]      FIG. 3  a sensor according to a third embodiment of the invention; 
           [0032]      FIG. 4  a sensor according to a fourth embodiment of the invention; 
           [0033]      FIG. 5  a sensor according to a fifth embodiment of the invention; 
           [0034]      FIG. 6  a sensor according to a sixth embodiment of the invention; 
           [0035]      FIG. 7  a sensor according to a seventh embodiment of the invention; and 
           [0036]      FIG. 8  a perspective view of an embodiment of a membrane used in the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0037]      FIG. 1  shows a first embodiment of a rotation angle and torsion angle sensor, or an angle of rotation and torsion angle sensor, according to the invention. A first shaft part  1  and a second shaft part  2 , coaxial to the first shaft part  1 , are connected to each other through a torsion bar  3 . If the shaft parts  1  and  2  are twisted relative to each other, the torsion bar  3  will rotate according to the torsional forces between the two shaft parts  1  and  2  (i.e., the acting torques of the two shaft parts  1  and  2 ). 
         [0038]    On the first shaft part  1 , is fixed a first membrane ring  4 . A second membrane ring  5 , having a larger diameter than the first membrane ring  4 , is connected to the first membrane ring  4  via a membrane  6 . The two membrane rings  4  and  5  form a first and a second connection with the membrane  6 . The membrane  6  is flexible in an axial direction and rigid in the circumferential direction, such that a rotation of shaft part  1  is transmitted through the first membrane ring  4 , to the membrane  6 , and onto the second membrane ring  5 . Thus, the second membrane ring  5  will follow the rotation of the first shaft part  1 . 
         [0039]    The second membrane ring  5  is concentric with the second shaft part  2 . The second membrane ring  5  is connected, through a funnel, or funnel-like, element  7  and a guide ring  8  to a first sensor disc  9 . The first sensor disc  9  is axially displaceably guided by the second shaft part  2 . The first sensor disc  9  rotates uniformly with the first shaft part  1 . The funnel element  7  is bridged in the axial direction of the torsion bar  3 . 
         [0040]    A first sensor  10 , which is attached to a fixed holder  11 , is associated with the first sensor disc  9 . In the illustrated embodiment, the first sensor disc  9  is a magnetic disk having a magnetization and the first sensor  10  is a magnetic sensor which produces an electrical signal. The electric signal corresponds to the axial position of the first sensor disc  9 . 
         [0041]    The first sensor disc  9  is, as mentioned, displaceable in the axial direction due to the axial flexibility of the membrane  6 . In order to achieve axial displacement during relative rotation between the first and second shaft parts  1  and  2 , a plurality of coupling elements  12  are provided, which couple the first sensor disc  9  with a second sensor, or annular, disc  13 . The second sensor disc  13  is coupled to the second shaft part  2 , rotating along with the second shaft part  2 , and is immovable in the axial direction. In the illustrated embodiment, the coupling elements  12  are rods, having at both ends hinges  14  and  15 , in which the coupling elements  12  are connected to the first sensor disc  9  at end hinges  14 , and the second sensor disc  13  at end hinges  15 . The coupling elements  12  are further bendable in a longitudinal direction, however, inextensible coupling elements can be used instead of rods and hinges  14  and  15 . 
         [0042]    If the two shaft parts  1  and  2  are synchronously rotated, (i.e., there is no torsion on the torsion bar  3 ), the first sensor disc  9  and the second sensor disc  13  rotate synchronously, with the sensor disc  9  in a neutral axial rest position. 
         [0043]    On the other hand, if the two shaft parts  1  and  2  are rotated relative to each other, the first sensor disc  9  and the second sensor disc  13  are rotated relative to each another as well, and the first sensor disc  9  is axially displaced according to a function of the torsion angle between the first shaft part  1  and the second shaft part  2  because of the flexible membrane  6  via the coupling elements  12 . Thereby the first sensor disc  9  moves in the axial direction from a neutral rest position by a distance which is a function of the torsion angle. This displacement is detected by the first sensor  10 , and outputted as an electrical signal. The mentioned function axial displacement versus torsion angle in this case is a cosine function. It is therefore advisable—as shown in FIG.  1 —to arrange the coupling members  12  in the neutral position relative to a rotational axis  21  at an inclination angle, so that even in small torsion angles, a sufficiently large axial displacement occurs. 
         [0044]    The absolute rotational position of the second shaft part  2  is measured by two sensor wheels  16  and  18 , which are in rotational engagement with the second sensor disc  13 . The second sensor disk  13  is a drive wheel, and in practice runs as a gear. The two sensor wheels  16  and  18  are also gear wheels which are in engagement with the gear formed by the second sensor disc  13 . Both sensor wheels  16  and  18  are associated with a respective sensor  17  or  19 , which detect the rotational position of the sensor wheels  16  and  18 . For example, the two sensor wheels  16  and  18  are magnetized, and the sensors  17  and  19  are magnetic sensors, each of which generate an electrical output signal corresponding to the rotational position of the sensor associated with the wheels  16  and  18 . The two sensor wheels  16  and  18  have different diameters, and in the case of gears different number of teeth, in order to measure in a conventional manner. Further, the two sensor wheels  16  and  18  have rotational angle ranges of more than 360°. The smaller sensor wheel detects, for example, a rotation angle range of 360°, while the larger sensor wheel is so designed that it is within the specified range, for example, three full rotations of the second shaft part 2, (i.e., 3 times 360°), makes one full rotation, whereby it can be determined within which full rotation (period), the second shaft part  2  is standing. 
         [0045]    In the illustrated embodiment, the two sensors  17  and  19  are mounted on a common fixed sensor support  20 . The common fixed sensor support  20  can also support the rotary axes  22  and  23  of the sensor wheels  16  and  18 . 
         [0046]    The two sensor wheels  16  and  18  can also be designed in a different known manner, for example, such that a sensor wheel, when going through the full measuring range of n*360° rotations to perform a number of m rotations and the other performs a number of m+1 rotations. 
         [0047]    In practice, magnetic sensors are most commonly used. However, in other embodiments it is possible to use optical sensors, in which the sensor disc  9  and the sensor wheels  16  and  18  have corresponding optically scannable marks. 
         [0048]    If above is spoken of axially, coaxial, etc., this always refers to the central axis  21 , which is also the axis of rotation for the two shaft parts  1  and  2 , the torsion bar  3 , the first membrane ring  4 , the second membrane ring  5 , the membrane  6 , the first sensor disc  9 , and the second sensor disc  13 . 
         [0049]    The embodiment of  FIG. 2  differs from that of  FIG. 1  essentially in that the axial displacement of the first sensor disc  9  is effected by a screw thread  25  which is provided between the guide ring  8  and a threaded sleeve  26 . The threaded sleeve  26  is fixedly connected to the second shaft part  2 . The threaded sleeve  26  has an external thread and the guide ring  8  has a matching internal thread. At a relative rotation between the two shaft members  1  and  2 , the guide ring  8 , and therefore the first sensor disc  9 , which is again detected by the sensor  10 , will be axially displaced due to the screw thread  25 . Again, this axial movement is made possible by the membrane  6 . 
         [0050]    Instead of a thread, a link guide can also be used. For example, one or more pins can be attached on the guide ring  8 , which is/are guided in one or more grooves of the thread  26 . 
         [0051]    The embodiment of  FIG. 3  illustrates the coupling between the membrane ring  5  and the wheel sensor disc  9  is made by hinged levers  27 , which are connected through hinges  28  and  29  on the membrane ring  5  and on an axially displaceable annular disc  8   a.  The levers  27  have, in the neutral position parallel to the central axis  21 , extending legs  31 , whose free ends are connected through the hinge  28  with the membrane ring  5 . Lever  27  further includes a second leg  32 , which is connected to the first leg  31  and substantially perpendicular to the first leg  31 . The free end of the second leg  32  is connected through the hinge  29  to the annular disc  8   a.  The leg  31  is pivotally mounted by a pivot pin  30  to the annular disk  13 , which is immovably fixed to the shaft part  2 . 
         [0052]    In comparison with the embodiment of  FIG. 1 , the present embodiment of  FIG. 3  achieves, during torsion between the two shaft parts  1  and  2 , a larger axial displacement of the ring plate  8   a,  of the affiliated guide ring  8  and of the sensor disk  9 , as the lever  27  forms a “transmission ratio” that is, during the pivoting of hinge  28 , hinge  29 , and thus the end point of the second leg  32 , takes a larger axial movement than the common junction point  33  of the two legs  31  and  32 . 
         [0053]    In the illustrated embodiment of  FIG. 3 , the annular disc  13  includes slits  34  extending through the leg  31  and the pivot points  30 . The length of the slits  34  in the circumferential direction is dimensioned such that the leg  31  can freely move in the full torsion area. 
         [0054]    The annular disc  13  is rotatably connected to the second shaft part  2  and is, as seen in the axial direction, arranged between the second membrane ring  5  and the annular disc  8   a.  The annular disc  8   a,  the guide ring  8 , and the sensor disc  9  move relative to the second shaft part  2  and are axially displaceable. Further, the annular disc  8   a,  the guide ring  8 , the sensor disc  9 , and the second shaft part  2  are connected with each other. The two sensor wheels  16  and  18  are driven in the same manner as in the embodiment of  FIG. 1 , by the annular disc  13  which is fixedly connected to the second shaft part  2 . 
         [0055]    In the embodiment of  FIG. 4 , on the two shaft parts  1  and  2 , respectively, are a drive wheel  40  and the annular disc  13 . Firmly fixed between the drive wheel  40  and the annular disc  13  is the torsion bar  3 . The annular disc  13  drives the two sensor wheels  16  and  18 , which are used in the same manner as in the above embodiments for determining the angle of rotation of the second shaft part  2 . The drive wheel  40 , connected to the first shaft member  1 , drives a driven wheel  42 , disposed coaxially with the sensor wheel  16 , and rotatable about the axis of rotation  22 . The driven wheel  42  is connected to the membrane  6  with a bearing ring  44  which is axially displaceable relative to the rotational axis  22  of the driven wheel  42 . The bearing ring  44  is connected with a magnetic pin  45  which is therefore also axially displaceable relative to the axis of rotation  22 . The magnetic sensor  10  is mounted on the fixed bracket  11 . The driven wheel  42  is held non-displaceably by an outer bearing  45 , which is axially relative to the axis of rotation  22 . The bearing ring  44 , coupled to membrane  6 , is connected to an annular disc  47 , which similarly is connected as in the embodiment of  FIG. 1 , by coupling elements  12  with the sensor wheel  16 . The annular disc  47  immediately follows the rotational position of the driven wheel  42  in direction of rotation due to the membrane  6 . The annular disc  47  can, however, move due to the coupling with the axially non-displaceable sensor wheel  16 , which is also held immovably in an outer bearing  46  in the axial direction and thus shifts the magnetic pin  45  in the axial direction. Therefore, with relative torsion of the two shaft parts  1  and  2 , the magnetic pin  45  is shifted. The magnetic sensor  10  detects this displacement and puts out a signal corresponding to the torsion between the two shaft parts  1  and  2 . Analogous to the embodiment of  FIG. 1 , the annular disc  47  can also be designed as a sensor disc similar to the sensor disc  9  of  FIG. 1 . In such an embodiment, the sensor  10  scans the axial position of the annular disc  47 , and is arranged opposite to the annular disc  47 . 
         [0056]    The diameter of the drive wheel  40  and the annular disc  13  are substantially equal, or in the case that the drive wheel  40  and the annular disc  13  are gear wheels, have an equal number of teeth. Likewise, the diameter or number of teeth of the sensor wheel  16  and the driven wheel  42  are the same. 
         [0057]    Briefly summarized, the coupling principle, as applied to the membrane  6  of  FIG. 1 , is applied to the coupling elements  12  on the sensor wheel  16  and the driven wheel  42  whose common axis of rotation  22  is parallel to the central axis  21  of the two shaft members  1  and  2 . 
         [0058]    The embodiment of  FIG. 5  differs from that of  FIG. 4  substantially in that the driven wheel  42  is coupled through a rigid membrane  6 ′ and the coupling elements  12  to the axially non-displaceable sensor wheel  16 . The driven wheel  42  is therefore axially movable relative to the common axis of rotation  22 . The magnetic pin  45  is fixedly connected to the driven wheel  42 . The driven wheel  42  is large enough in its axial height, that even with axial displacement, the driven wheel  42  is always engaged with the drive wheel  40 . 
         [0059]    The embodiment of  FIG. 6  is similar to that of  FIG. 4 . Further the embodiment of  FIG. 6  incorporates the threaded coupling principle of the embodiment of  FIG. 2 . The driven wheel  42  and the sensor wheel  16  are supported by external bearings  46  and  48 , which are axially fixed to the common axis of rotation  22 . 
         [0060]    The driven wheel  42  is connected, through the membrane  6 , to the axially displaceable bearing ring  44 , which in this embodiment is designed as a threaded sleeve with an internal thread. The bearing ring  44  is further connected to the magnetic pin  45 . The bearing ring  44  and the magnetic pin  45  are thus axially displaced relative to the axis of rotation  22 . The sensor wheel  18  is connected to a threaded pin  49 , which in this embodiment has an external thread which engages the internal thread of the bearing ring  44 . The sensor wheel  16  and the threaded pin  49  are held immovably in the axial direction through the outer bearing  46 . At relative rotation between the driven wheel  42  and the sensor wheel  16 , the bearing ring  44  shifts due to the threaded connection to the threaded pin  49  in the axial direction, and thus so does the magnetic pin  45 , whose axial position is detected by the sensor  10 . 
         [0061]    In the embodiment of  FIG. 7 , the driven wheel  42 , together with the magnetic pin  45 , is axially displaceable by a rigid membrane  6 ′ analogous to the embodiment of  FIG. 5 . The sensor wheel  16  is axially undisplaceable and again includes the threaded pin  49 , which engages in the bearing ring  44  of the output wheel  42 . The bearing ring  44  has a corresponding internal thread and is rigidly connected to the driven wheel  42 . The magnetic pin  45  is also rigidly connected to the bearing ring  44 . At relative rotation between the sensor wheel  16  and the driven wheel  42 , the driven wheel  42  moves together with the bearing ring  44  and the magnetic pin  45  in the axial direction. Such movement is detected by the sensor  10 . 
         [0062]      FIG. 8  shows an embodiment of the membrane  6 , which has a circular inner ring  50 , a concentric circular outer ring  51  and a plurality of radial webs  52  connecting the two rings  50  and  51 . The two rings  50  and  51  in this embodiment form connections  53  and  54  of the membrane  6 . The membrane  6  can be punched from a planar plate of a resilient material such as spring steel. Due to the described shape of the inner ring  50  and the outer ring  51 , the inner ring  50  and the outer ring  51  are rigidly connected to each other as far as possible in the circumferential direction. The inner ring  50  and the outer ring  51  are movable relative to each other in the axial direction by bending of the webs  52 .