Abstract:
A method for detecting a phase angle difference between a first periodic measurement signal and a second periodic measurement signal, wherein, for the purpose of determining a torque applied to a shaft, the two periodic measurement signals describe a rotation of the shaft at an axial distance from one another including superimposing a periodic auxiliary signal which simulates a previously known rotational speed for the shaft on the first periodic measurement signal in order to form a superimposition signal, and determining the phase angle difference on the basis of the superimposition signal and the second measurement signal.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is the U.S. National Phase Application of PCT International Application No. PCT/EP2013/076867, filed Dec. 17, 2013, which claims priority to German Patent Application No. 10 2012 224 108.6, filed Dec. 20, 2012 and German Patent Application No. 10 2013 219 017.4, filed, Sep. 20, 2013, the contents of such applications being incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a sensor for emitting an electrical signal on the basis of a travel to be detected, in particular of an angle. 
       BACKGROUND OF THE INVENTION 
       [0003]    WO 2006/029 946 A1 incorporated by reference herein discloses an angle sensor having a signal generator magnet and a measuring circuit with evaluation electronics for evaluating an angular position of the signal generator magnet. The signal generator magnet does not have any direct mechanical connection to the measuring circuit, with the result that from the point of view of the evaluation electronics the signal generator magnet hovers above the measuring circuit. 
       SUMMARY OF THE INVENTION 
       [0004]    An aspect of the invention aims to improve the known angle sensor. 
         [0005]    According to one aspect of the invention, a sensor for emitting an electrical signal based on a travel to be detected comprises a housing which spans an interior space and an exterior space, a signal generator which penetrates the housing from the exterior space into the interior space and which has a travel sensor element in the exterior space and a field signal generator element in the interior space, wherein the travel sensor element is configured to rotate the field signal generator element with respect to the housing on the basis of the travel to be detected, an evaluation circuit for detecting a physical field which is output by the field signal generator element, and a moisture protection element for protecting a gap between the housing and the signal generator against penetrating moisture. 
         [0006]    The specified sensor is based on the idea that it could be used on a vehicle for detecting a relative position of a wheel of the vehicle with respect to its chassis. In this way, an active chassis control system could be implemented with which the classic conflict of objectives between a sporty and a comfortable adjustment of the chassis and suspension could be resolved. 
         [0007]    However, it becomes apparent here that such sensors are very susceptible to faults and therefore have a relatively short service life. Within the scope of the specified sensor it is recognized here that a main cause of the short service life is the moisture penetrating into the sensor which damages the evaluation circuit of the sensor and makes it functionally incapable. This penetrating moisture is caused by the fact that the sensor is mounted on the underside of the vehicle and is subjected directly to dirt and moisture which is thrown up from the road. 
         [0008]    The specified sensor is therefore based on the idea of protecting said sensor and, in particular, its evaluation circuit against penetrating moisture by a moisture protection element. 
         [0009]    The moisture protection element can be embodied in any desired fashion. In a particularly advantageous fashion, the moisture protection element comprises a labyrinth which is configured to lengthen a flowpath of the penetrating moisture in the gap. Such a labyrinth can be implemented by means of simple geometric changes to the housing and/or signal generator and therefore requires in principle no new elements, with the result that the moisture protection element could be implemented in the specified sensor in a cost-neutral fashion. 
         [0010]    In one development of the specified sensor, the labyrinth is embodied from a first sleeve which is embodied on the signal generator, and a second sleeve which is embodied on the housing and which engage one in the other. Two such sleeves would lengthen the abovementioned gap between the housing and the signal generator in an axial fashion with the result that the entry of the penetrating moisture into the interior space is delayed to a high degree. 
         [0011]    In another development, the specified sensor comprises a bypass element which is configured to conduct the penetrating moisture past the gap. In this way, the avoidance of the penetration of the moisture could be improved further. 
         [0012]    In a further development of the specified sensor, the bypass element is a drainage channel which is embodied in at least one of the two sleeves. This drainage channel can be embodied in a cost-neutral fashion on the sleeves by means of simple geometric changes, without additional technical elements being necessary. The drainage channel can, for example, conduct the water circumferentially past the gap, wherein the water would then drop down from the drainage channel underneath the gap without penetrating said gap. 
         [0013]    In one preferred development of the specified sensor, the corresponding other sleeve has a projection which engages in the drainage channel. In this way, the previously mentioned gap is lengthened even further and the labyrinth effect is therefore enhanced further. 
         [0014]    In order to enhance the labyrinth effect even further, at least one of the two sleeves, but preferably both bushings, can engage respectively in a circumferential groove which is correspondingly embodied on the housing and/or on the signal generator. 
         [0015]    In yet another development of the specified sensor, the housing and/or the signal generator is embodied conically running away from an inlet point of the gap. In this way, the quantity of moisture which can potentially enter the gap at all is reduced. 
         [0016]    It is particularly preferred to embody the conical profile here on the inside and on the outside, with the result that moisture penetrating the gap on the inside is conducted back again to the gap. 
         [0017]    According to a further aspect of the invention, a vehicle comprises one of the specified sensors. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The properties, features and advantages of this invention which are described above and the way in which they are achieved become clearer and more clearly comprehensible in relation to the following description of exemplary embodiments which are explained in more detail in relation to the drawings, wherein: 
           [0019]      FIG. 1  shows a schematic view of a vehicle with a chassis control system, 
           [0020]      FIG. 2  shows part of a CPS sensor, 
           [0021]      FIG. 3  shows part of an alternative CPS sensor, 
           [0022]      FIG. 4  shows part of a further alternative CPS sensor, and 
           [0023]      FIG. 5  shows part of yet another CPS sensor. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    Identical technical elements are provided with identical reference symbols in the figures and described only once. 
         [0025]    Reference is made to  FIG. 1  which shows, in a schematic view, a vehicle  54  with a chassis control system  56 . 
         [0026]    Within the scope of this chassis control system  56 , lifting movements, pitching movements and rolling movements of a chassis  58  with respect to a road (not illustrated further) on which wheels  60  of the vehicle  54  roll in a positionally fixed fashion in a vertical axis  62  are to be minimized in order to improve the driving properties of the vehicle  54  when travelling in a direction of travel  64 . 
         [0027]    For this purpose, the chassis control system has, in a fashion known, for example, from DE 10 2005 060 173 A1, incorporated by reference herein, a control device  66  which, in the present embodiment composed of angle sensors  2  which are arranged on each wheel  60 , receives rotational angles  68  which describe a relative position of the corresponding wheel  60  with respect to the chassis  58 . On the basis of the differences between these rotational angles  68 , the control device  66  determines whether the chassis  58  is moving in the vertical axis  62 , that is to say is carrying out a lifting movement, or whether the chassis  58  is rolling or pitching, and controls. In this case, the control device  66  calculates a counter-movement, counteracting this lifting movement, rolling movement and/or pitching movement, and controls, with suitable control signals  70 , active spring struts  72  which are arranged on the wheels  60 , in order to compensate this counter-movement with the chassis  6 . For example, the spring struts which are known from DE 101 22 542 B4, incorporated by reference herein, can be used as active spring struts  72 . 
         [0028]    In order to take into account lifting movements, rolling movements and/or pitching movements caused by the position of the road, for example during cornering, a suitable setpoint value  74  can be fed to the control device. 
         [0029]    The angle sensors  2  are embodied in the present embodiment as chassis position sensors  2 , referred to below as CPS sensors  2 . The chassis position sensor measures a relative position of the chassis  58  of the vehicle  2  with respect to its chassis and suspension or one of the wheels  60 . One of these CPS sensors  2  will be described in more detail below with reference to  FIGS. 2 to 5 . 
         [0030]      FIG. 2  illustrates an embodiment of the CPS sensor  2 . 
         [0031]    The CPS sensor  2  comprises a housing  4  which can be connected, for example, in a positionally fixed fashion to the chassis  58  of the vehicle  54 , and a signal generator  6  which detects the abovementioned relative position of the chassis and suspension or wheel  60  of the vehicle  54  with respect to the chassis  58  and therefore the housing  4 . For this purpose, the signal generator  6  is mounted in rotatable fashion with respect to the housing  4 . 
         [0032]    The housing  4  comprises a housing wall  8  which separates an interior space  10 , in which an evaluation circuit (not illustrated further) is accommodated, from an exterior space  12 . 
         [0033]    In addition, a first housing sleeve  14  and a second housing sleeve  16  which is arranged concentrically with respect to the latter project axially from this housing wall, which housing sleeves  14 ,  16  together form a housing groove  18  which lies radially between the latter. In addition, a housing flange  20  projects concentrically inward from the first housing sleeve  14 , against which a third housing sleeve  22  adjoins its radially inner side. In this third housing sleeve  22 , a rotary bearing  24  which is embodied, for example, as a sliding bearing is secured. 
         [0034]    The signal generator  6  comprises a lever  26  which is illustrated in a cut-off form in  FIG. 2  which can be moved, for example, by the wheel  60  and therefore can be rotated with respect to the housing  4 . A first signal generator sleeve  28  and a second signal generator sleeve  30  which is arranged concentrically with respect to the latter project axially from the lever  26 , which signal generator sleeves  28 ,  30  form a signal generator groove  32  radially between them. In this context, a signal generator bead  31  is formed at the end of the first signal generator sleeve  28  lying axially opposite the lever  26 . A bushing  33 , in which a shaft  34  is held by means of a press fit, is arranged concentrically within the two signal generator sleeves  28 ,  30 . A field signal generator element in the form of a magnet  36  is held in a positionally fixed fashion with respect to the shaft  34  at the end lying axially opposite the lever. 
         [0035]    By virtue of the design mentioned above, the magnet  36  can be rotated by means of the shaft  34  with the lever  26  with respect to the housing  4  which is arranged in a positionally fixed fashion with respect to the chassis of the vehicle. In this context, the housing  4  and the signal generator  6  are arranged axially with respect to one another in such a way that the first signal generator sleeve  28  engages axially in the housing groove  18 , the second housing sleeve  14  engages axially in the signal generator groove  32 , with the result that a labyrinth-like gap  37  is formed between the housing  4  and the signal generator  6 . The shaft  34  carries out here the movement of the lever  26 , arranged in the exterior space  12 , into the interior space  10  with respect to the magnet  36 . The latter emits a physical field, in the form of a magnetic field, which changes as a function of the position of the lever  26  and therefore of the magnet  36 , which magnetic field is sensed by the evaluation circuit (not illustrated further) and, for example for the determination of the relative position, is evaluated in a manner known per se. 
         [0036]    In order to detect the relative position of the chassis and suspension with respect to the chassis, the CPS sensor  2  must be disadvantageously arranged on an underfloor side of the vehicle at which it is subjected to a comparatively large amount of penetrating moisture  38 . If this moisture  38  were to penetrate the interior space  10  of the housing  4 , it could damage the evaluation circuit (not illustrated further) and make the CPS sensor  2  functionally incapable. For this reason, the labyrinth-like gap  37  is embodied, which gap  37  increases the travel for the moisture  38  and therefore lengthens the time by which the moisture can reach the evaluation circuit. 
         [0037]    In addition, the signal generator bead  31  forms, together with the lever  26  and the first signal generator sleeve  28 , a further moisture protection element which is formed as a bypass. Said bypass is embodied as a drainage channel  40  which runs on the radial outerside of the signal generator sleeve  28  and which collects the moisture which penetrates from the outer side  12  and conducts it circumferentially around the shaft  34  past the labyrinth-like gap  37  on the radial outer side of the signal generator sleeve  28 , with the result that the moisture cannot even penetrate said gap  37 . 
         [0038]    As yet a further moisture protection element, it is possible, in the present embodiment, to arrange a seal in the form of a Y seal  42  radially between the shaft  34  and the second housing sleeve  14 , which seal seals off the interior space  10  of the housing  4  physically with respect to the penetrating moisture. 
         [0039]      FIG. 3  illustrates part of an alternative CPS sensor  2 . This alternative CPS sensor  2  only comprises the second housing sleeve  16  and the first signal generator sleeve  28  between which the labyrinth-like gap  37  is embodied. 
         [0040]    For this purpose, in the second signal generator sleeve  16  a further drainage channel  40  is embodied, into which a projection  44  projects radially in the present embodiment. Although this projection  44  requires an undercut  46  which has to be manufactured in a costly fashion, the labyrinth-like gap  37  is nevertheless increased further by the projection  44 . 
         [0041]      FIG. 4  shows part of a further alternative CPS sensor  2 . The lever  26  cannot be seen on the signal generator in  FIG. 4 . However, instead,  FIG. 4  shows the evaluation circuit which is provided with the reference symbol  48 . Electrical contacts in the form of what are referred to as pressfits  50 , by means of which the evaluation circuit  48  can be connected to a superordinate control device, such as, for example, an engine controller of the vehicle, project from said evaluation circuit  48 . Only one of these pressfits  50  is provided with a reference symbol in  FIG. 4 . 
         [0042]    In  FIG. 4 , the signal generator bead  31  is embodied in a conical fashion and projects over an input  52  of the labyrinth-like gap  37 . In this way, the possibility of moisture penetrating into the labyrinth-like gap  37  is reduced further. 
         [0043]      FIG. 5  illustrates part of yet another CPS sensor  2 . In this CPS sensor  2 , the first signal generator sleeve  28  is embodied running conically from the inlet point  52  of the labyrinth-like gap  37  to the lever  26 . This conical shape is embodied here within the gap  37  and toward the exterior space  12 , with the result that moisture is conducted away from the inlet point  52  of the labyrinth-like gap  37  at the exterior space, and is conducted to the inlet point  52  within the labyrinth-like gap  38 .