Abstract:
A tire sensor module having a circuit carrier, on or in which at least one sensor element is attached for measuring a measured variable, an antenna for transmitting sensor signals to a receiving unit of the vehicle, and a housing, in whose housing inner chamber the circuit carrier is received, the antenna being provided in the housing material of the housing or on a housing side of the housing.

Description:
FIELD OF THE INVENTION 
     The field of the invention relates to a tire sensor module. 
     BACKGROUND INFORMATION 
     Tire sensors are used in particular for measuring the tire pressure, i.e., as so-called tire pressure monitoring systems (TPMS). They are typically attached as sensor modules to the rim or the valve of the tire and transmit their data wirelessly with the aid of an antenna to a receiving unit of the vehicle, which relays the data to a central control unit of the vehicle. 
     The antenna is generally provided as a wire outside the sensor. During the mounting of the sensor module in the tire by being vulcanized in, for example, the antenna is therefore to be oriented in accordance with its design, which correspondingly results in complex mounting steps. 
     SUMMARY OF THE INVENTION 
     According to the exemplary embodiments and/or the exemplary methods of the present invention, the antenna of the tire sensor module is provided in or on the housing of the tire sensor module, i.e., it is not provided in the housing inner chamber or outside the housing, but rather is provided in the housing material, i.e., integrated, or is implemented on a housing side. In particular, it may be implemented on the housing interior side. 
     The antenna thus may not be deformed or changed in its orientation during vulcanization, as is possible with configurations outside the housing. Furthermore, the antenna also does not occupy any installation space in the housing interior chamber, in which the circuit carrier having at least the sensor element and possibly further components is attached. Therefore, a larger housing interior chamber is available as the sensor installation space at a given housing size. The antenna may nonetheless be designed with a substantial antenna length, in that it extends with the corresponding length in or on the housing. 
     According to a specific embodiment, at least the housing, but advantageously both the housing and also the circuit carrier, is designed to be rotationally symmetric. The antenna may run in a coil or helix in or on the housing and thus occupy a large antenna length. With a helix shape of this type, the antenna properties, in particular the emission characteristic, are essentially isotropic and/or uniform in the plane perpendicular to the coil axis. 
     The tire sensor module according to the present invention may thus be attached without orientation in the tire; it may be vulcanized into the rubber material, in particular in the area of the running surface, for example. 
     According to a first alternative specific embodiment, the antenna may be implemented on one housing side, which may be the housing interior side, as an antenna metal layer. A laser direct structuring method (LDS) is advantageously used for this purpose, at least one area of the housing being manufactured from a laser-activatable thermoplastic. 
     A manufacturing method of this type has the essential advantage that the geometry of the antenna may be adapted flexibly to the various applications. In the laser direct structuring method, a writing exposure method is used, so that only the data set, e.g., a CAD/CAM data set of the laser controller, is to be altered for different variants. 
     According to a second alternative specific embodiment thereto, the antenna may be laid as a metallic inlay part in the injection molding die and then extrusion coated by the housing plastic. This results in a simple and cost-effective manufacturing method. 
     The circuit carrier may be in contact with the antenna using a conductive adhesive bond between the circuit carrier and housing, the gluing allowing secure accommodation of the circuit carrier in the housing. Instead of the conductive adhesive bonds, pressure contacts, clamp connections, or press-in connections are also possible, so that no gluing is required during the final mounting of the circuit board in the housing. Furthermore, a contactless, in particular an inductive or capacitive connection of the antenna to the circuit carrier is also possible, so that no complex electrical contacting is required between the circuit carrier and the sensor housing. The mounting of the circuit carrier in the housing is thus significantly simplified. 
     The circuit carrier or the substrate may be a circuit board in particular, on which still further components, in particular an analysis and control ASIC and an RF ASIC may be attached in addition to the sensor element or sensor IC. Functions of this type may fundamentally also be partially or entirely integrated on the sensor IC, however. 
     Fundamentally, the tire sensor module according to the present invention may implement all measuring applications of tire sensors, in particular for measuring the (tire interior) pressure, temperature, or accelerations and/or vibrations. The various functions may also be combined if multiple sensor elements are used. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a tire sensor module with an open housing in a perspective view. 
         FIG. 2  shows a perspective view of a housing part having an antenna according to a first embodiment. 
         FIG. 3  shows a cross section of the tire sensor module of the first embodiment having a coated antenna. 
         FIG. 4  shows a cross section of the tire sensor module of the second embodiment having an embedded antenna. 
         FIG. 5  shows a flow chart of the production method according to the present invention according to the two embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     A tire sensor module  1  according to the present invention has a housing  2  having an upper housing part  2   a  and a lower housing part  2   b , which are bonded to one another in a weld bond  3  and define a housing chamber  4  between them. Housing  2  is not designed to be hermetically sealed, at least for pressure measurements. 
     A circuit carrier  6 , e.g., a circuit board  6  or also a ceramic substrate, on which a sensor element  7  (sensor IC) and further components are attached, e.g., an analysis and control ASIC  8  for recording the measured values of sensor element  7 , possibly also for analyzing these measured signals, an RF ASIC  9 , and an oscillator  10 , is accommodated in housing chamber  4 . Circuit carrier  6  may be placed on a shoulder  11  of housing part  2   a , for example. 
     Sensor element  7  may be used for measuring different measured variables, in particular for measuring the tire pressure, as well as for measuring the internal temperature in the tire or accelerations and/or vibrations. Tire sensor module  1  may in particular also have multiple sensor elements  7  for measuring multiple status variables or measured values of this type. 
     An antenna  14 ,  24  is implemented in or on housing  2  according to the present invention, i.e., not in housing inner chamber  4  or outside housing  2 , but rather in the housing material or on the interior or exterior side. According to the first embodiment of  FIGS. 1 through 3 , antenna  14  is implemented as a metal layer on interior side  16  of housing  2 , e.g., of first housing part  2   a . For this purpose, housing  2 —or a housing part  2   a —is manufactured from a laser-activatable plastic, in particular a thermoplastic, e.g., from polymer types LCP, PA6/6T, or PBT. Plastics of this type are doped using metal-organic substances, which, after being exposed by the laser as activated seed crystals, make subsequent electroless metal plating possible. The metal-organic substance may be dissolved or extremely finely dispersed in the plastic; it may be a chelate complex compound of a noble metal, e.g., based on palladium or copper. Furthermore, a surface structure which is capable of high adhesion during the subsequent wet-chemical metal coating is produced at the plastic-metal interface during laser structuring. 
     According to the second specific embodiment of  FIG. 4 , antenna  24  is embedded as a metallic insert part  24  in a housing part  2   a , for which purpose it is inserted in the injection molding die used during manufacturing. 
     Antenna  14 ,  24  may be designed in both specific embodiments as a helix antenna or a screw-like antenna in particular, for which purpose housing  2  is advantageously cylindrical. A substantial antenna length may thus be implemented, the length accordingly resulting from the inner circumference of housing  2  and the number of turns or coils. 
     Antenna  14 ,  24  is connected to circuit carrier  6  in an antenna connection  18 . According to one embodiment, electrical contacts are possible. An electrical contact of this type may be produced on the one hand in that a conductive adhesive is used at least in the area of the contacting of antenna  14 ,  24  with circuit carrier  6 , i.e., circuit carrier  6  is fastened to shoulder  11  of housing  2  using an adhesive bond  12 , adhesive bond  12  or a partial area of adhesive bond  12  being electrically conductive and causing circuit carrier  6  (or a die pad or contact pad of circuit carrier  6 ) to be in contact with a contact pad  17  of housing  2 , at which antenna  14  or  24  is connected. An underfiller may additionally be applied below the circuit carrier to increase the mechanical stability. 
     Alternatively thereto, designs of antenna connection  18  as pressure contacts, clamp connections, or press-in connections are also possible, so that no adhesive bond  12  is required during the final mounting of circuit carrier  6  in housing  2  and the positioning and fastening of circuit carrier  6  and contacting of antenna  14 ,  24  may be performed entirely via clamp and catch mechanisms. 
     Furthermore, antenna connection  18  may also be designed to be contactless, in particular inductive or capacitive, so that the complex electrical connection between circuit carrier  6  and antenna  14 ,  24  is dispensed with. 
     Tire sensor module  1  may act in particular as a transponder, which receives query signals RF 1  via antenna  14 ,  24  and produces transmission signals RF 2  from measurement signals of sensor element  7 , which are in turn transmitted via antenna  14  or  24 . 
     The manufacturing methods of the two specific embodiments are described in  FIG. 5 . The production according to the first specific embodiment is performed in that (after the start in step S 0 ) housing  2  or a housing part  2   a  is injection molded in step S 1  from a laser-activatable thermoplastic, and interior side  16  of housing  2  or housing part  2   a  is subsequently exposed in step S 2  as the first processing step of the laser direct structuring method (LDS), after which a metal, e.g. copper, is deposited on the exposed points in step S 3  using wet chemistry. The copper may be reinforced and provided with a surface finish made of chemical nickel and immersion gold, for example. In step S 4 , circuit carrier  6  is inserted in housing  2  or housing part  2   a , antenna  14  also being in contact with circuit carrier  6 . In step S 5 , the housing is closed by welding housing parts  2   a ,  2   b.    
     According to the second specific embodiment, antenna  24  is laid as a metallic insert part in a casting mold or injection molding die in step S 7 , subsequently embedded in housing part  2   a  in step S 8 , and circuit carrier  6  is then inserted in housing  2  or housing part  2   a  so that antenna  14  is in contact with circuit carrier  6  according to step S 4 . 
     Thus manufactured tire sensor module  1  may in particular be vulcanized into the rubber material of a tire  30  in a subsequent step S 6 . Because tire sensor module  1  is designed to be rotationally symmetric in the specific embodiment shown and its antenna  14  is implemented as at least essentially rotationally symmetric, namely it has an essentially uniform emission characteristic in the plane perpendicular to the coil axis because of the helical shape or coil shape, it is also possible to attach tire sensor module  1  in the tire without orientation in specific planes. Tire sensor module  1  according to the present invention may thus also be vulcanized into the running surface, e.g., in the area of the steel belt.