ANDERSON, S.C. — More stringent emissions requirements have brought about more advanced and highly sensitive oxygen sensors, as well as the placement of more than one O2 sensor in some vehicles.
In early February, Bosch invited the automotive press to Anderson, S.C., to tour two of their O2 sensor facilities to see how thimble and planar O2 sensors are made and to better understand how O2 sensors work. Later that month, the Bosch facility made its 125 millionth O2 sensor.
O2 sensors signal the engine control module (ECM) that the air/fuel mixture is too lean or too rich. The ECM then determines the action. Bosch Director of Product Management Chuck Ruth says all gasoline vehicles have had O2 sensors since the late 1980s. Since OBD II has been enforced the number of O2 sensors per vehicle has doubled. Fifty-one percent of vehicles in operation are OBD II.
In 1991, half of vehicles in production were heated O2 sensors and half were unheated O2 sensors. Today all vehicles in production have heated O2 sensors, which have a higher response rate than unheated sensors. The quicker the response, even if it’s milliseconds, the less harmful emissions are sent into the air, says Ruth.
There are two styles of heated O2 sensors –– thimble and planar. More stringent emissions requirements have brought about more sensitive O2 sensors. Planars are rapidly becoming the dominant sensor type for the OEMs. This year 49 percent of production will use planar styles, Ruth estimates. Planars, which are flat layered ceramic elements, provide lean or rich exhaust gas readings about 10 to 12 seconds after an engine starts. They then send readings to the ECM several times per second.
The next generation of O2 sensors will be wideband, but the OEMs are not yet ready to implement them. Wideband sensors are also called “pumping” sensors, because they pump emissions into the sensors. A wideband sensor provides a signal to the ECM that’s virtually proportional to the amount of oxygen in the exhaust stream. According to Bosch, this allows the ECM to precisely control the air-fuel ratio to maintain optimum performance. Bosch said its wideband O2 sensor responds to changes in less than 100 milliseconds.
Bosch offers a universal heated O2 sensor program for the aftermarket. The company provides 14 types of universal heated sensors: four three-wire thimble, nine four-wire thimble and one four-wire planar. These 14 part numbers meet specific exacting OE operating requirement and cover over 280 million sensor units in operation, appropriate for replacement with universal heated sensors. Bosch’s O2 sensor catalog has 1,400 applications dating back to 1997.
In January Bosch was awarded a patent on its sealed, submersible “quick-connection” system for Bosch universal heated oxygen sensors. Featuring a unique sealing system and specially formulated, heat resistant Posi-Lock
