A New Design of Optical In-Cylinder Pressure Sensor for Automotive Applications

This paper describes a new design of in-cylinder pressure sensor for automotive applications using optical technology. The technology has been applied to a direct injection diesel engine and compared against reference sensors. The rapid expansion in use of fiberoptics in other industries, primarily telecommunications, has supported the development and cost reduction of the technology to the point where it can be considered for automotive applications.

Automotive environments are much harsher than standard telecommunications, so the challenge is to develop and package the technology to operate reliably in an engine bay environment.

The sensor system consists of a passive sensor head employing a silicon diaphragm responding to the applied pressure and an integrated optical signal processing chip which contains an optical interferometer, light source, and photodiode. The sensor head returns the input light to the optical interferometer via an optical fiber converting the phase shift induced by the diaphragm deflection into an electrical signal output.

The initial results from the sensors show good performance against reference sensors.