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Sensor element, in particular seat occupancy detection sensor element

  • US 8,698,643 B2
  • Filed: 10/24/2012
  • Issued: 04/15/2014
  • Est. Priority Date: 10/26/2011
  • Status: Active Grant
First Claim
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1. A sensor element, in particular a seat occupancy detection sensor element (14), comprising:

  • a double-body compression spring (46);

    a base member (18) having a substantially cylindrical recess (26) for receiving the double-body compression spring (46); and

    a slidable member (56) having a force application side (58) and an inside facing the base member (18);

    a measuring coil (44) arranged in the substantially cylindrical recess (26) and surrounded by the double-body compression spring (46) and having a wound coil wire (42); and

    a current generating, measuring and evaluating unit connected to the wound coil wire (42) of the measuring coil (44);

    wherein the double-body compression spring (46) abuts the base member (18) with its first end on the side of the base member and is fixed to the slidable member (56) with its second end on the side of the slidable member and is adapted to be compressed by a force acting on the force application side (58) of the slidable member (56), from an initial state in which the double-body compression spring (46) has an uncompressed initial spring length or an initial spring length compressed by a predetermined extent, into a compressed state of shorter spring length;

    wherein the spring wire ends (54) of the double-body compression spring (46) are connected to each other in electrically conducting manner so as to form a spring coil (46);

    wherein the measuring coil (44) and the spring coil (46) constitute an inductively coupled coil assembly (44, 46); and

    wherein the current generating, measuring and evaluating unit is designed such that it applies a defined alternating current to the measuring coil (44) so that an alternating current is induced in the double-body compression spring (46), that it measures the voltage on the measuring coil (44) that is proportional to the overall impedance of the inductively coupled coil assembly, and ascertains from said overall impedance the force acting on the force application side (58) of the slidable member (56).

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