Pressure sensor screw-fitting into IC engine block - has membrane moving rod acting on piezoelectric transducer

摘要

A piezo-electric transducer (20) is connected via a rod (26) to a membrane (15). The sensor is fot fitting into the engine block (13) and detects knocking. The pressure in the piston chamber acts on the membrane, whose resulting movement is transferred by the rigid rod to the piezo-electric transducer where it is converted into an electrical signal. The transducer consists of a piezo-electric plate on a metal plate (24). The rod is made of steel and may be hollow. The bimorphous transducer has an external thread (18) that allows it to screw into a threaded hole in the engine block. The metal plate faces the piston chamber and is in good thermal contact with the sensor's casing (17), which acts as a heatsink. The membrane has a built-in curvature that does not change sign when the membrane is heated by the burning gases. The membrane consists of a thin sheet of titanium, tantalum or tungsten. A ring may be located between the rod and the membrane. The advantage lies in simplicity and in the sensor's being fitted permanently into the engine.