Image Number 3 for United States Patent #4192140.
Apparatus and method for the protection of an exhaust gas reactor, for example a catalytic element or a thermal reactor, disposed in the exhaust conduit of an internal combustion engine which is operated on a lean air/fuel mixture. This invention provides means for protection of the exhaust gas reactor from excessive temperatures under deceleration conditions by regulating the air/fuel mixture ratio in the induction means of the engine whereby to restrict the oxidation which occurs at the reactor. One method according to the invention comprises adding supplementary air to the induction means for a limited time after the throttle is closed under deceleration conditions, and after an initial delay, adding supplementary fuel to the induction means while the engine continues to operate under deceleration conditions. In addition, thermally sensitive means responsive to the temperature of the exhaust gas reactor serves to maintain the air/fuel ratio of the mixture in the induction means at a relatively richer value whenever there is indication of overheating of the exhaust gas reactor.