Automotive Oxygen Sensor Turns 30

BROADVIEW, IL /PRNewswire/ -- One of the most significant engine management devices developed to control harmful automotive exhaust emissions—the oxygen sensor, or O2 sensor—was invented 30 years ago and is in use now more than ever. In fact, practically every vehicle manufacturer today uses one, and often two or more such sensors per vehicle.

The oxygen sensor for automotive use was pioneered by a leading automotive supplier, Robert Bosch Corp., as an essential weapon in the battle to rein in emissions. First installed in 1976 on the Volvo 240/260 series, subsequently it was expanded to sensors installed upstream and downstream of the catalytic converter.

"With the California Air Resources Board (CARB) and U.S. Environmental Protection Agency requiring reduction of harmful tailpipe emissions, vehicle manufacturers welcomed a device that could accurately measure oxygen in the exhaust. This helps maximize engine and converter efficiency when mounted upstream, and monitor converter efficiency when mounted downstream," said Warren Suter, director of product management, engine systems group at Bosch. Today's automobiles and light trucks have at least two sensors, many have three, four, or more.

The automotive oxygen sensor measures the amount of oxygen in the exhaust and signals the engine control unit to adjust the air/fuel ratio to near the ideal, or stoichiometric, mixture of 14:7:1, for maximum efficiency.

"And, when it is positioned both upstream and downstream of the catalytic converter, as in late-model vehicles," said Suter, "it also monitors the catalytic converter function." An oxygen sensor, therefore, helps ensure maximum combustion efficiency with minimum exhaust emissions, which leads to optimum fuel economy and longer catalytic converter life.

"For the past 30 years, as vehicle fuel management systems and emissions requirements evolved, Bosch continued to play a leadership role in refining and advancing oxygen sensor technology," Suter said.

Having introduced the oxygen sensor for new vehicles in 1976, Bosch offered the first sensor to the aftermarket in 1980. Early oxygen sensors were the unheated "thimble" type, which took 2-4 minutes to reach operating temperature.

In 1982, Bosch introduced the heated thimble type sensor and cut the warm-up time to less than a minute. The heated planar oxygen sensor, launched in 1997, reduced the time to 10 seconds and cut harmful warm-up emissions by 50%. The following year, Bosch brought to market the wide-band oxygen sensor, which measures exhaust gas composition in various concentrations rather than simply "rich" or "lean."

To support such widespread use, Bosch's oxygen sensor program covers over 524 million units in operation and 1430 aftermarket part numbers, and offers more original-equipment-fit sensors than any other manufacturer. "This year, Bosch manufactured its 400 millionth automotive oxygen sensor," Suter said.

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