Exhaust emissions control system

Abstract

Exhaust emissions control system provides effective control of hydrocarbons, carbon monoxide, and nitrogen oxides by adjusting the air-fuel ratio of an internal combustion engine having a catalytic converter in its exhaust path in response to the percentage oxygen content of the exhaust gases as measured by a voltage generating oxygen sensor positioned in the exhaust path. The electrical signal produced by the oxygen sensor is compared to a set point signal which corresponds to the desired oxygen content which prevails when the conversion of the exhaust gases is optimized and a correcting step adjustment is made in the air-fuel ratio when there is a difference in the signals. To minimize hunting and still provide a relatively rapid response, the system incorporates a time delay to permit each adjustment made in the air-fuel ratio to be reflected in the output of the exhaust gases before the oxygen content of such exhaust gases is sensed preliminary to make succeeding step adjustments. By providing a time delay equal to the time required for a predetermined number of engine revolutions, the length of the delay can be varied greatly so as to closely approximate the different response times required by the engine system at idle or at high speed.

Dependencies are inferred from the claim text.