Exhaust air purifier for internal combustion engine

Abstract

There is provided an exhaust air purifier for an internal combustion engine that reduces the frequency of estimation of an amount of accumulated particulate matter, and hence energy consumption involved in the estimation of the amount. Based on a difference ΔP 1 between the exhaust pressures before and after a DPF 12 and based on a second amount of accumulated PM, QPM 2, estimated based on a temperature increase arising when the PM is temporarily heated, first map data for estimating a first amount of accumulated PM, QPM1, based on the difference ΔP 1 between the pressures before and after the DPF 12 is corrected so that a amount of accumulated PM when the difference ΔP 1 between the exhaust pressures is obtained equals the second amount of accumulated PM, QPM 2. This further improves the accuracy of the first amount of accumulated PM, QPM 1, estimated by “the process of estimating the first amount of accumulated PM” performed subsequently. This makes it possible to more accurately determine whether to perform “the process of estimating the second amount of accumulated PM.”

1 . An exhaust air purifier for an internal combustion engine, the purifier comprising:
 a particulate matter collecting unit that collects particulate matter from exhaust gas from the internal combustion engine;   an exhaust pressure detecting unit that detects exhaust pressures before and after the particulate matter collecting unit;   an exhaust temperature detecting unit that detects exhaust temperature downstream of the particulate matter collecting unit;   a heating unit that increases the temperature of the exhaust gas passing through the particulate matter collecting unit; and   a control unit that estimates the amount of accumulated particulate matter collected by the particulate collecting unit, and controls the temperature of the heating unit,   wherein the control unit estimates a first amount of accumulated particulate matter based on the difference between the exhaust pressures before and after the particulate matter collecting unit, which difference has been calculated using values detected by the exhaust pressure detecting unit, and based on first map data pre-stored in a memory, which map data represent the interrelation between the amount of accumulated particulate matter in the particulate matter collecting unit and the difference between the exhaust pressures before and after the particulate matter collecting unit;   when the first amount of accumulated particulate matter has reached a threshold, the control unit causes the heating unit to temporarily heat the particulate matter accumulated in the particulate matter collecting unit and also estimates a second amount of particulate matter based on an increase in temperature at the time of heating of the particulate matter, and based on second map data pre-stored in the memory, which map data represent the interrelation between the increases in the temperature at the time of the heating of the particulate matter and the amount of accumulated particulate matter in the particulate matter collecting unit; and   based on the second amount of accumulated particulate matter and based on the difference between the exhaust pressures before and after the particulate matter collecting unit, the difference having been calculated based on the values detected by the exhaust pressure detecting unit, the control unit corrects the first map data representing the interrelation between the amount of accumulated particulate matter in the particulate matter collecting unit and the difference between the exhaust pressures before and after the particulate matter collecting unit.