On-board gas composition sensor for internal combustion engine exhaust gases

An internal combustion engine for a motor vehicle, comprising, in combination:

• a combustion chamber for burning an air/fuel mixture;
• an exhaust conduit for passing exhaust gases form the combustion chamber to atmosphere;
• an air/fuel mixture control means responsive to input signals for controlling the ratio of air and fuel in the air/fuel mixture;
• and
• an on-board gas composition sensor for monitoring oxygen content levels in the exhaust gases in the exhaust conduit for generating a sensor output signal as one of said input signals to the air/fuel mixture control means, the gas composition sensor comprising;
• sensor means comprising a sensor body of porous high-temperature fluorescent inorganic oxide ceramic exposed to the exhaust gases in the exhaust conduit, for emitting an optical fluorescence signal responsive to oxygen content level in the exhaust gases upon exposure of the sensor body to excitation light in a 350 to 525 nm wavelength range at 400.degree.-650.degree. C.
• light source means remote from the sensor body, for generating the excitation light, comprising a light emitter selected from a laser diode and a light emitting diode;
• an electrical resistance heater proximate the sensor body for heating the sensor body to a temperature between 400.degree.-650.degree. C.;
• fluorescence detector means remote from the sensor body, comprising a photospectrometer having an array detector for receiving the optical fluorescence signal from the sensor means and generating a response signal, and integration means for receiving and spectrally integrating the response signal over a range of 540 to 1000 nm over a preselected time interval of 0.5 to 4.0 seconds and generating an exhaust gas oxygen content output signal in response thereto;
• excitation detector means for detecting the excitation light and generating a compensation signal corresponding to the intensity of the excitation light for adjusting the exhaust gas oxygen content output signal in response thereto for generating said sensor output signal of the gas composition sensor;
• and
• light conveyor means comprising a fiber-optic cable for carrying both the excitation light from the light source means and the optical fluorescence signal from the sensor body, the fiber-optic cable comprising:
• a first portion extending between the light source means and a fiber-optic coupler;
• a second portion extending between the fiber-optic coupler and the sensor body, the sensor body being fused to the fiber-optic cable;
• a third portion extending between the fiber-optic coupler and the fluorescence detector means, having an optical filter for filtering out the excitation light carried by the fiber-optic cable;
• and
• a fourth portion extending between the fiber-optic coupler and the excitation detector.