AUTOMOTIVE SENSORS FOR EMISSIONS CONTROL AND MONITORING APPLICATIONS
J. H. Visser, D. J. Kubinski, E. P. Murray, R. F. Novak, R. E. Soltis,
Research and Advanced Engineering, Ford Motor Company
MD3028 / SRL, 2101 Village Road, Dearborn MI 48124, USA
Abstract
Many different types of sensors are used in today’s automobiles. These automotive sensors are used in four major areas: active and passive safety systems, powertrain control systems, emissions control and monitoring systems, and climate control systems. This presentation will start with a short and very broad automotive sensor overview and then discuss in more depth sensors related to emissions control and monitoring systems. Most emissions standards around the world regulate both tailpipe and evaporative emissions. Increasingly, On-Board Diagnostics (OBD) is required. OBD systems check the vehicle’s emissions performance and alert the driver to any malfunction that causes the vehicle to fail emissions standards.
The discussion on sensors for emissions control and monitoring will start with a description of the current low-emission gasoline vehicles, in which the Heated Exhaust Gas Oxygen (HEGO or UEGO) or lambda sensor plays a crucial role in controlling Air-to-Fuel (A/F) ratio. This tight A/F control enables catalytic converters to remove harmful HC, NOx, and CO emissions with efficiencies often in excess of 99%. In addition, these sensors also play an important role for OBD. The various types of zirconia-based lambda sensors as used by automotive companies around the world will be presented and explained.
To improve fuel economy and enable the use of alternative fuels, while at the same time still meeting the increasingly stringent emissions standards, many new automotive sensors will be needed. Some of these sensors are currently close to being production-ready, while others are still very much in the research and development stage. The sensor needs for advanced gasoline, diesel, HCCI (homogeneous charge compression ignition), H2 (both fuel cells and internal combustion engine), and hybrid applications will be discussed. As with all automotive components, cost and durability severely limit the possible solutions (typical exhaust gas environment conditions will be shown). The principles of and problems with various sensing technologies will be presented. The different sensing technologies for exhaust gas NOx and NH3, and H2 leak detection sensors (all three high-priority new sensors) will be discussed in detail.