Importance

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Abstract

An ignition coil, spark plug, and pressure sensor for an internal combustion engine are integrated into a single assembly and mounted directly on a plug hole of an internal combustion engine. A hard spark plug shell serves as a magnetostrictive section for pressure detection. A radially polarized biasing magnet is disposed adjacent the spark plug shell thereby generating an initial flux through a sensing winding. The sensing winding is wound about the lower end of the coil case to sense changes in the induction characteristics of the spark plug shell as a result of pressure changes in the cylinder. A first passive method of sensing pressure whereby the flux change due to the permeability change generates a signal voltage in the sensed coil. This voltage is proportional to the time rate of change of pressure which is integrated to produce a cylinder pressure waveform. A second active method employs an oscillator to drive the sensing circuit with a frequency at least ten times that of the pressure signal content. The frequency or amplitude of this signal is then modulated in response to the induction property change of the spark plug shell the induction changes The second method is capable of detecting both static and dynamic pressure.

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First Claim