Method and system for controlling an emission control device based on depletion of device storage capacity

A system for filling and purging an emission control device so that the device is substantially filled to capacity with a constituent gas of the engine-generated exhaust gas during a fill time and is substantially emptied of previously-stored constituent gas during a subsequent purge time, the system comprising:

• a sensor operative to generate a signal representative of an oxygen concentration in the exhaust flowing through the device;
• a control module programmed to calculate the depletion of device capacity based on a calibrated device filling rate in engine speed load regions multiplied by the time spent in the region and further programmed to continuously sum the calculated capacity depletion and schedule a purge event when a predetermined percentage of capacity less than 100% is depleted, wherein the module is programmed to modify the calibrated device filling rate as a function of air-fuel ratio, EGR and spark advance, wherein the module is further programmed to modify the calculated depletion as a function of device temperature, wherein the module further includes:
• a map of the device filling rate over an engine speed and load operating range using a representative calibration for device temperature, air-fuel ratio, EGR and spark advance;
• and wherein the depletion of device capacity is a time weighted sum based on the amount of time spent in a given speed-load region utilizing the mapped filling rates in each region modified to account for the difference between existing and calibrated operating conditions.

A method of controlling the fill and purge time of an emission control device located upstream of a switching-type oxygen sensor in an exhaust treatment system for an internal combustion engine, wherein the emission control device stores a quantity of a constituent gas of the engine-generated exhaust gas during a first engine operating condition up to a device capacity, and releases stored constituent gas during a second engine operating, the method comprising:

• calculating device capacity utilization in accordance with the following equation:
• RSM = M 1 ⁡ ( t ) ⁢ ∑ k = 1 k = P ⁢ M 2 ⁡ ( AFR ) ⁢ M 3 ⁡ ( EGR ) ⁢ M 4 ⁡ ( SPK ij ) ⁢ R ij ⁡ ( % / s ) ⁢ t k
• terminating device filling and scheduling a device purge when the capacity of the device is substantially reached;
• and
• determining an optimum purge time based on the amplitude of the voltage output of the sensor.