Magnetostrictive sensor, in particular for measuring torque, and its application in an engine misfire, knock or roughness detection method and apparatus

摘要

A method and apparatus for comparing torsional stress/strain states of a power transmitting member of an internal combustion engine to detect an abnormal combustion condition, including misfire, knock or roughness. Statistical processing steps may be used to detect an abnormal combustion event including : calculating a mean and standard deviation for a set of signals related to the torsional stress induced in the power transmitting member, calculating a difference between a later signal and the mean, calculating a ratio of the difference to the standard deviation, and comparing the ratio to a threshold. The ratio so obtained from a given cylinder may further be compared with one or more other such ratios from other cylinders. On other words, the auto-correlation and/or cross-correlation techniques may be used. A magnetostrictive sensor may preferably be used to obtain the signals relating to the torsional stress in the power transmitting member, such as the engine crankshaft. In addition, the magnetostrictive sensor may include windings to cancel induced electromagnetic interference signals. The magnetostrictive sensor may also generate signals relating to the position of the power transmitting member in addition to the torsional stress in the power transmitting member. Spatial integration techniques may be used to obtain torsional stress/strain signals which are independent of the rotational speed of the power transmitting member. Spatial interaction may be performed using variable amplifiers, variable attenuators, switched capacitors or other techniques.