A load sensor for measuring engine cylinder pressure and vehicle seat occupant weight in a nonintrusive manner that is easily adaptable to existing vehicle components and occupancy support structures. The sensor of the invention provides a toroidal-shaped ferromagnetic steel core that defines a hollow space within which an excitation coil and a detection coil are wound. For engine cylinder pressure sensing, this toroidal sensor is placed on a spark plug, much in the nature of a washer, and is clamped between the spark plug and the spark plug seat in the chamber. For seat occupant weight sensing, the sensor is placed under a seat leg around a fastening bolt, again much in the nature of a washer, and is clamped between the bolt and the floor of the vehicle. Changes in the load or force produced by the cylinder pressure or the occupant weight, alters the stress in the steel core of the sensor. These stress changes in turn induce changes in the magnetic properties of the steel core. Non-linear harmonic analysis of the stress induced magnetic property changes is made and derives the cylinder pressure or occupant weight after suitable calibrations. The cylinder pressure measurements can then be used to facilitate an efficient operation of the internal combustion engine through the modification of timing, fuel mixture, etc. The use of the device in conjunction with occupant safety systems would provide a weight value sufficient to characterize the appropriate or inappropriate activation of an air bag system or the like.
Hegeon Kwun