Closed-loop method and system for purging a vehicle emission control

摘要

A vehicle exhaust treatment system includes an emission control device featuring at least one upstream NO_x-storing “brick,” and a downstream NO_x-storing “brick” that is substantially smaller in nominal capacity than the upstream brick. An oxygen sensor positioned between the upstream and downstream bricks generates an output signal representing the concentration of oxygen in the device. A controller selects a rich operating condition to purge the device of stored NO_x, and deselects the rich, NO_x-purging engine operating condition in response to the sensor output signal, preferably after an additional time delay calculated to provide sufficient excess hydrocarbons to release substantially all stored NO_x from the downstream brick.