High Temperature Piezoresistive Beta-Sic-On-Soi Pressure Sensor For Combustion Engines

For measuring the cylinder pressure in combustion engines of automobiles a high temperature pressure sensor has been developed. The sensor is made of a membrane based piezoresistive beta-SiC-on-SOI (SiCOI) sensor chip and a specially designed housing. The SiCOI sensor was characterized under static pressures of up to 200 bar in the temperature range between room temperature and 300 degrees C. The sensitivity of the sensor at room temperature is approximately 0.19 mV/bar and decreases to about 0.12 mV/bar at 300 degrees C. For monitoring the dynamic cylinder pressure the sensor was placed into the combustion chamber of a gasoline engine. The measurements were performed at 1500 rpm under different loads, and for comparison a quartz pressure transducer from Kistler AG was used as a reference. The maximum pressure at partial load operation amounts to about 15 bar. The difference between the calibrated SiCOI sensor and the reference sensor is significantly less than 1 bar during the whole operation.