Patent ID: 8756917

Claim:
An exhaust gas treatment system for an internal combustion engine, comprising: an exhaust gas conduit in fluid communication with, and configured to receive exhaust gas from, the internal combustion engine; a particulate filter assembly in fluid communication with the exhaust gas conduit and configured to receive exhaust gas flowing therethrough, the particulate filter assembly comprising: an electrically heated catalyst that is configured to receive a flow of electric current, to be heated by the flow of electric current, and to thereby increase a temperature of the exhaust gas; a particulate filter disposed downstream of the electrically heated catalyst to remove particulate material from the exhaust gas; a hydrocarbon injector in fluid communication with the exhaust gas conduit upstream of the electrically heated catalyst and configured to inject excess hydrocarbon into the exhaust gas flowing therethrough; an air pump in fluid communication with the exhaust gas conduit upstream of the electrically heated catalyst and configured to deliver a flow of air to the exhaust gas conduit to increase the volumetric gas flow rate through, and decrease the heat residence time in, the particulate filter; a controller configured to operate the hydrocarbon injector, the electrically heated catalyst and the air pump based on predetermined exhaust gas flow rates, temperature thresholds and particulate loadings within the particulate filter; a flow rate sensor in fluid communication with the exhaust gas in the exhaust conduit and in signal communication with the controller to generate a signal indicative of the flow rate in the exhaust conduit; and a temperature sensor in fluid communication with the exhaust gas in the particulate filter assembly and in signal communication with the controller to generate a signal indicative of the temperature in the particulate filter assembly; wherein the controller is configured to: receive the signal indicative of the temperature in the particulate filter assembly and to compare the temperature in the particulate filter assembly to the predetermined temperature threshold; receive the signal indicative of the flow rate in the exhaust conduit and to compare the flow rate in the exhaust conduit to the predetermined flow rate threshold; when either (i) the temperature in the particulate filter assembly is greater than the predetermined temperature threshold or (ii) the flow rate in the exhaust conduit is less than the predetermined flow rate threshold, then (iii) decrease the flow of electric current to the electrically heated catalyst, (iv) decrease the excess hydrocarbon supplied via the hydrocarbon injector, and (v) activate the air pump; and when both (vi) the temperature in the particulate filter assembly is less than the predetermined temperature threshold and (vii) the flow rate in the exhaust conduit is greater than the predetermined flow rate threshold, then (viii) deactivate the air pump.