Method for controlling the level of oxygen stored by a catalyst within a catalytic converter

摘要

The catalyst control method of the invention continuously estimates a level of oxygen stored by a catalyst within a catalytic converter. The estimated oxygen stored by the catalyst is compared to a predetermined threshold and positive or negative deviations in the oxygen amount from the threshold is determined. When a positive deviation from the threshold amount is detected, the air/fuel ratio flowing into an engine (16) is decreased. Correspondingly, when a negative deviation is detected, the air/fuel ratio flowing into the engine (16) is increased. The amount of oxygen stored by the catalyst is determined by analyzing signals from a first gas sensor (28) positioned upstream from a catalytic converter (34) and a second gas sensor (30) positioned downstream from the catalytic converter (34). An engine control unit (10) integrates an expression for the mass flow rate of excess oxygen into the catalytic converter (34). Engine control unit (10) applies a change in air/fuel ratio to maintain the oxygen level on the catalyst within the catalytic converter (34) at a desired level.