Abstract:
A sensor for sensing a physical transmitter field dependent on a physical quantity to be measured, including: a sensor circuit for sensing the transmitter field and for outputting a sensor signal dependent on the transmitter field a circuit carrier having a first region in which at least a part of the sensor circuit is supported and a second region in which at least a first mechanical interface and a second mechanical interface for connecting the circuit carrier to a retainer are arranged, and a noise resistance element, which is arranged between the first region and the second region and which is designed to conduct structure-borne noise entering via the first mechanical interface to the second mechanical interface.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the U.S. National Phase Application of PCT/EP2015/064419, filed Jun. 25, 2015, which claims priority to German Patent Application No. 10 2014 213 217.7, filed Jul. 8, 2014, the contents of such applications being incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a sensor for sensing a physical transmitter field which is dependent on a physical variable to be measured. 
       BACKGROUND OF THE INVENTION 
       [0003]    WO 2010/037 810 A1, which is incorporated by reference discloses a sensor having a sensor circuit which is configured to output a sensor signal which is dependent on a physical variable to be measured, via a physical transmitter field which is dependent on the physical variable to be measured. 
       SUMMARY OF THE INVENTION 
       [0004]    An aspect of the invention is to improve this sensor. 
         [0005]    According to one aspect of the invention, a sensor for sensing a physical transmitter field which is dependent on a physical variable to be measured comprises a sensor circuit for sensing the transmitter field and for outputting a sensor signal which is dependent on the transmitter field, a circuit carrier having a first region in which at least part of the sensor circuit is supported, and a second region in which at least a first mechanical interface and a second mechanical interface for connecting the circuit carrier to a retainer are arranged, and a noise-resistance element which is arranged between the first region and the second region and is configured to conduct structure-borne noise entering via the first mechanical interface to the second mechanical interface. 
         [0006]    The specified sensor is based on the idea that sensors, such as the specified sensors, are usually used in environments in which structure-borne noise oscillations occur owing to other electrical components such as, for example, capacitors or other mechanical components such as, for example, actuators. These structure-borne noise oscillations can move the sensor circuit and therefore influence not only the actual physical transmitter field but also the sensor signal and therefore falsify the measurement of the physical variable to be measured. This can be observed, in particular, in the case of inertial sensors in which the physical transmitter field constitutes the physical variable which is actually to be measured, such as, for example, the accelerations of a vehicle in the spatial axes. 
         [0007]    This is where the specified sensor comes in with the proposal that the structure-borne noise is not to be allowed to penetrate as far as the sensor circuit but instead is to be conducted as far as possible past the sensor circuit. This is achieved by virtue of the fact that the sensor is divided into two regions, wherein the first region at least partially supports the sensor circuit, and the second region is connected to the surroundings, such as, for example, a vehicle, in which the physical variable which is to be measured is to be sensed. A noise-resistance element between these two regions acts like a wall for the structure-borne noise which enters the second region, with the result that the structure-borne noise remains true to the principle that it will always follow the path with the least resistance and moves past the wall and exits again from the second region. 
         [0008]    Therefore, the structure-borne noise does not occur at the noise-resistance element and therefore cannot influence the measurement of the physical variable to be measured. As a result, the measurement of the physical variable to be measured becomes significantly more precise. 
         [0009]    In one development of the specified sensor, the circuit carrier is embodied as a leadframe, and the noise-resistance element is embodied as a slit in the leadframe. A leadframe is a circuit carrier whose conductor tracks are formed by means of cutting methods, such as punching, from a plate-shaped basic material. In this context, the noise-resistance element which is embodied as a slit can also be formed within the scope of a cutting method such as punching, with the result that the noise-resistance element can be manufactured with the same tools as the circuit carrier itself and therefore no relatively large manufacturing costs are incurred for the implementation of the noise-resistance element. 
         [0010]    In one particular development of the specified sensor, the slit is designed to run around the first region, and the second region is connected to the first region via at least one web. As a result of the slit which runs around, the first region in which the sensor circuit is arranged is mounted in a virtually floating fashion with respect to the second region, wherein owing to the principle involved a negligibly small sound bridge, the at least one web, remains over which structure-borne noise can still penetrate from the second region into the first region. At the same time, this floating support damps further the structure-borne noise which penetrates the first region because the penetrating structure-borne noise can cause the first region to oscillate less strongly owing to its mechanical inertia and the floating support. 
         [0011]    In another embodiment, preferably in order to assist the floating support of the structure-borne noise the specified sensor can comprise a mechanical decoupling element which encapsulates the first region of the circuit carrier, the sensor circuit and at least partially the noise-resistance element which is preferably embodied as the previously mentioned slit. By means of the mechanical decoupling element, the floating support explained above can be assisted further, wherein the mechanical decoupling element can also damp other sound waves which are not brought about by structure-borne noise. 
         [0012]    For this purpose, the mechanical decoupling element should be a material which is as soft as possible. Within the scope of one expedient development of the specified sensor, the mechanical decoupling element could comprise a silicone mass which is particularly cost-effective but satisfies all the necessary requirements for noise decoupling of the second region from the first region of the specified sensor. 
         [0013]    In order to improve the noise decoupling further, in a particular development the mechanical decoupling element of the specified sensor could comprise a noise-decoupling film on which the first region of the circuit carrier is supported. Then, for example the silicone mass could be sprayed onto the side of the circuit carrier lying opposite the noise-decoupling film, which can be implemented with high precision and in a simple fashion with mass production methods. The first region of the circuit carrier would then be accommodated between the silicone mass and the noise-decoupling film, as in a sandwich. 
         [0014]    In an additional development of the specified sensor, an electrical reference potential is applied to at least one of the two mechanical interfaces. In this way, the mechanical interface, which is, in any case, connected to the first region of the circuit carrier and therefore to the sensor circuit, for example via the web mentioned above, can also be used to implement an electrical function. 
         [0015]    Furthermore, in yet another development the sensor can comprise a decoupling component such as, for example, a noise-decoupling film which can be the same as or different than the noise-decoupling film mentioned above. That is to say, for example, part of the sensor circuit, such as, for example, the measuring pickup or pickups of the sensor circuit, can be supported directly on the noise-decoupling film mentioned above. Then, for example a recess in which this part of the sensor circuit is then inserted could be formed in the circuit carrier. In this way, the noise decoupling can be increased further. 
         [0016]    The specified sensor can be enclosed in a protective mass, for example made of thermoset, by which the specified sensor can be largely protected against weather phenomena. 
         [0017]    The specified sensor can be a wheel speed sensor or an inertial sensor for a vehicle. 
         [0018]    According to a further aspect of the invention, a vehicle comprises a specified sensor. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0019]    The properties, features and advantages of this invention described above, and the way in which they are achieved, become clearer and more easily understandable in conjunction with the following description of the exemplary embodiments which are explained in more detail in conjunction with the drawings, in which: 
           [0020]      FIG. 1  shows a schematic view of a vehicle having a vehicle movement dynamics control system, 
           [0021]      FIG. 2  shows a schematic illustration of an inertial sensor in the vehicle in  FIG. 1 , 
           [0022]      FIG. 3  shows an embodiment of the inertial sensor in  FIG. 2  in a schematic sectional illustration, 
           [0023]      FIG. 4  shows the inertial sensor in  FIG. 3  on a printed circuit board in a schematic side view, 
           [0024]      FIG. 5  shows an alternative embodiment of the inertial sensor in  FIG. 2  in a schematic sectional illustration, 
           [0025]      FIG. 6  shows a further alternative embodiment of the inertial sensor in  FIG. 2  in a schematic sectional illustration, and 
           [0026]      FIG. 7  shows yet another alternative embodiment of the inertial sensor in  FIG. 2  in a schematic plan view. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    In the figures, identical technical elements are provided with the same reference numbers and described only once. 
         [0028]    Reference is made to  FIG. 1  which shows a schematic view of a vehicle  2  with a vehicle movement dynamics control system which is known per se. Details on this vehicle movement dynamics control system can be found, for example, in DE 10 2011 080 789 A1, which is incorporated by reference. 
         [0029]    The vehicle  2  comprises a chassis  4  and four wheels  6 . Each wheel  6  can be slowed down with respect to the chassis  4  by means of a brake  8  which is attached in a positionally fixed fashion to the chassis  4 , in order to slow down a movement of the vehicle  2  on a road (not illustrated further). 
         [0030]    In this context, it can be found, in a manner known to a person skilled in the art, that the wheels  6  of the vehicle  2  lose their grip and the vehicle  2  even moves away from a trajectory, predefined, for example, by means of a steering wheel (not shown further) as a result of understeering or oversteering. This is avoided by control loops, which are known per se, such as ABS (anti-lock brake system) and ESP (electronic stability program). 
         [0031]    In the present embodiment, the vehicle  2  has for this purpose rotational speed sensors  10  on the wheels  6  which sense a rotational speed  12  of the wheels  6 . In addition, the vehicle  2  has an inertial sensor  14  which senses inertial data, referred to below as vehicle movement dynamics data  16 , of the vehicle  2 , which data can comprise, for example, a pitching rate, a rolling rate, a yaw rate, a lateral acceleration, a longitudinal acceleration and/or a vertical acceleration of the vehicle  2 . 
         [0032]    On the basis of the sensed rotational speeds  12  and vehicle movement dynamics data  16 , a controller  18  can determine, in a manner known to a person skilled in the art, whether the vehicle  2  is slipping on the underlying surface or is even deviating from the abovementioned predefined trajectory and can correspondingly react thereto with a controller output signal  20  which is known per se. The controller output signal  20  can then be used by an actuation device  22  in order to actuate, by means of actuation signals  24 , actuating elements such as the brakes  8  which react to the slipping and the deviation from the predefined trajectory in a manner known per se. 
         [0033]    The controller  18  can be integrated, for example, into an engine controller, known per se, of the vehicle  2 . The controller  18  and the actuation device  22  can also be embodied as a common control device and optionally integrated into the engine controller mentioned above. 
         [0034]    In order to simplify the explanations below, it should be assumed, in a non-restrictive fashion, that the inertial sensor  14  senses, as vehicle movement dynamics data  16 , the lateral acceleration  26  which is indicated in  FIG. 2  and which acts on the vehicle and the yaw rate  28  with which the vehicle  2  rotates about its vertical axis because these are usually used within the scope of the stability program mentioned above. 
         [0035]    Although the invention has been explained in more detail with reference to the inertial sensor  14 , the invention can be applied to any desired sensors such as, for example, the specified rotational speed sensors  10 . 
         [0036]    A possible principle for the inertial sensor  14  will be explained in more detail below with reference to  FIG. 2 . 
         [0037]    In order to sense the lateral acceleration  26 , a lateral acceleration measuring pickup  30  is arranged in the inertial sensor  14 . The lateral acceleration measuring pickup  30  is subjected to a physical transmitter field in the form of a centrifugal force field  32  which acts on the lateral acceleration measuring pickup  30  and accelerates with the lateral acceleration  26  which is to be sensed and which acts on the vehicle  2 . The sensed lateral acceleration  26  is subsequently output to a signal conditioning circuit  34 . 
         [0038]    In order to sense the yaw rate  28 , a coriolis acceleration measuring pickup  36  is arranged in the inertial sensor  14 . The coriolis acceleration measuring pickup  36  is subjected to a physical transmitter field in the form of a coriolis force field  38 . In response to the coriolis force field  38 , the coriolis acceleration measuring pickup  36  outputs a transmitter signal  40  which then can be converted into the yaw rate  28  in an evaluation circuit  42  which is, if appropriate, also associated with the coriolis acceleration measuring pickup  36 . An example as to how the yaw rate  28  can be sensed on the basis of a coriolis force field  38  is described in document DE 10 2010 002 796 A1, which in incorporated by reference, for which reason a description will not be provided here for the sake of brevity. The sensed yaw rate  28  is also output to the signal conditioning circuit  34 . 
         [0039]    In the signal conditioning circuit  34 , the lateral acceleration  26  and yaw rate  28  which are acquired in this way can be post-processed in order, for example, to reduce the noise band interval and to increase the signal strength. The lateral acceleration  26  and yaw rate  28  which are conditioned in this way can then be output to an interface  44  which then transmits the two acquired signals as vehicle movement dynamics data  16  to the controller  18 . This interface  44  could be constructed, for example, on the basis of the PSI5 standard or the CAN standard. 
         [0040]    An embodiment of the inertial sensor  14  will be explained in more detail below with reference to  FIG. 3 . 
         [0041]    Within the scope of the present embodiment, the two measuring pickups  30 ,  36  and the signal conditioning circuit  34  form a sensor circuit  46  which is supported on and connected to a circuit carrier embodied as a leadframe  48 . Under certain circumstances, connections which cannot be implemented on the leadframe  48  can be implemented here by means of electrical lines in the form of bonding wires  50 . The interface  44  can be integrated into the signal conditioning circuit  34  and embodied as an application-specific integrated circuit, referred to as ASIC (application-specific integrated circuit)  34  below. 
         [0042]    The sensor circuit  46  can also be encapsulated by a mechanical decoupling material  51 , also referred to as globe top mass  51 , in the form of a silicone material which can in turn be encapsulated conjointly in an injection molding press material  52 , such as a thermoset in the form of an epoxy resin  52 . 
         [0043]    Finally, corresponding contact-forming means, such as small legs  54  shown in  FIG. 2 , for making electrical contact with a circuit such as, for example, the controller  18 , project from the inertial sensor  14 . 
         [0044]    Reference is made to  FIG. 4  on the basis of which possible falsification of the vehicle movement dynamics data  16  is to be explained in more detail. 
         [0045]    The inertial sensor  14  which senses the lateral acceleration  26  and/or the yaw rate  28  as vehicle movement dynamics data  16  could be soldered directly, using a reflow soldering process known per se, onto a printed circuit board  56  on which, for example, the controller  18  could also be implemented. Ceramic capacitors  58  could be additionally located on this printed circuit board  56 . In addition, the printed circuit board  56  could be connected via a screwed-on attachment  60  to other technical elements in the vehicle  2  such as, for example, an electrical valve and/or a housing  62  which is indicated in  FIG. 4 . 
         [0046]    It has become apparent that structure-borne noise  64 , generated by connected capacitors, such as the ceramic capacitor  58  and/or the other technical elements such as the abovementioned electrical valve which can be embodied, for example, as a solenoid valve, and/or vehicle body oscillations of the chassis  4 , can be conducted via the circuit board  56  and the small legs  54  to the leadframe  48  and from there to the measuring pickups  26 ,  28 . 
         [0047]    The structure-borne noise  64  excites the two measuring pickups  26 ,  28  to experience oscillations which are superimposed on the centrifugal force field  32  and the coriolis force field  38  and can therefore influence the lateral acceleration  26  to be sensed and/or the yaw rate  28  to be sensed. This superimposition of the transmitter fields  32 ,  38  can therefore give rise to a faulty sensor signal in the form of the vehicle movement dynamics data  16 , which can in turn give rise to incorrect reactions of the controller  18 . 
         [0048]    Therefore, the oscillations which are excited by the structure-borne noise  64  should be avoided as far as possible. 
         [0049]    This should be explained in more detail below with reference to  FIG. 5  which shows the inertial sensor  14  in an alternative embodiment. The coriolis acceleration measuring pickup  36  has been omitted in  FIG. 5  only for the sake of brevity and clarity. 
         [0050]    Within the scope of the inertial sensor  14  shown in  FIG. 5 , the oscillations which are excited by the structure-borne noise  64  are to be damped with a noise-resistance element  66 . This noise-resistance element  66  is embodied as a slit  66 , running around the sensor circuit  46 , in the leadframe  48 , with the result that the leadframe  48  is divided into a first region  68  and a second region  70 . The two regions  68 ,  70  can be connected to one another here via thin webs  72 , such as can be seen, for example, in  FIG. 7 . 
         [0051]    The printed circuit board  48  is supported on a noise-decoupling film  74  underneath the sensor circuit  46 , wherein the noise-decoupling film  74  and the globe top material  51  can be in contact in the slit  66  which runs around. The second region  70  of the leadframe  48  is fixedly connected to the printed circuit board  56  via the small legs  54  which are not indicated in  FIG. 5 , and this is indicated by fixed bearings  76 . In contrast, the first region  68  of the first region  68  is mounted in a floating fashion by the slit  66  which runs around, with the result that said first region  68  cannot be excited to oscillate by the structure-borne noise  64 . Consequently, the measuring pickups  30 ,  36  cannot be excited to oscillate either and the vehicle movement dynamics data  16  can be falsified. 
         [0052]    In order to increase the noise decoupling further, as shown in  FIG. 6  on the basis of the lateral acceleration measuring pickup  30 , the measuring pickups  30 ,  36  can be arranged directly on the noise-decoupling film  74 . For this purpose, a corresponding recess  78 , in which the corresponding measuring pickup  30 ,  36  can then be accommodated, can be formed in the first region  68  of the leadframe  48 . 
         [0053]    As shown in  FIG. 7 , the individual measuring pickups  30 ,  36  can be accommodated in a single measuring pickup circuit, wherein the signal conditioning circuit  34  outputs the individual vehicle movement dynamics data items  16 , acquired in this way, to electrical interfaces  80  via bonding wires  50 . In addition, the leadframe  48  can be connected to a reference potential  82 , for example at one of the fixed bearings  76 .