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 ΔP1 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 ΔP1 between the pressures before and after the DPF12 is corrected so that a amount of accumulated PM when the difference ΔP1 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, QPM1, 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.”

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The disclosure of Japanese Patent Application No. 2007-096085 filed on Apr. 2, 2007 including the specification, drawings and abstract is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to exhaust air purifiers for internal combustion engines and, more particularly, relates to exhaust air purifiers that collect particulate matter from exhaust gas from a diesel engine and remove the particulate matter by burn.[0004]2. Description of the Related Art[0005]Conventionally, this type of an exhaust purifier for an internal combustion engine estimates the amount of accumulated particulate matter collected by a particulate matter collecting unit, and performs a burning process when the estimated amount reaches a predetermined value.[0006]Examples of such a method include one in which the amount of accumulated particulate matter is estimated based on the ...

AI Technical Summary

Benefits of technology

[0009]The present invention has been made in view of the problems of the known technology discussed above. It is therefore an object of the present invention to provide an exhaust air purifier for an internal combustion engine, the purifier being designed so as to reduce the frequency of estimation of the amount of accumulated particulate matter, thereby reducing energy consumption involved in the estimation.

[0014]According to the first aspect of the present invention, when the second amount of accumulated particulate matter is estimated based on an increase in temperature at the time of temporary heating of the particulate matter, the first map data for estimating the amount of accumulated particulate matter based on the difference between the pressures of exhaust before and after the particulate matter collecting unit is corrected according to the difference between the exhaust pressures upstream and downstream of the particulate matter collecting unit, and according to the estimated second amount of accumulated particulate matter. In other words, using the first map data and the difference between the exhaust pressures upstream and downstream of the particulate matter collecting unit ensures more accurate estimation of the first amount of accumulated particulate matter in the subsequent estimation. Accordingly, a comparison between the first amount of accumulated particulate matter, estimated using the first map data, and a predetermined threshold makes it possible to correctly determine whether to estimate the second amount of accumulated particulate matter based on the increase in the temperature at the time of temporary heating of the accumulated particulate matter. This reduces the frequency of estimation of the second amount of accumulated particulate matter, and hence energy consumption involved in the estimation of the second amount.

[0015]In the exhaust air purifier according to the invention, when a second amount of accumulated particulate matter to be temporarily heating is estimated, first map data for estimating a first amount of accumulated particulate matter based on the difference between the pressures of exhaust before and after the particulate matter collecting unit is corrected to remove any error in estimation. A comparison between the first amount of accumulated particulate matter, estimated using the corrected first map data, and a threshold, makes it possible to correctly determine whether to estimate the second amount of accumulated particulate matter based on an increase in the temperature at the time of temporary heating of the accumulation of the particulate matter. This reduces the frequency of estimation of a second amount of accumulated particulate matter, and hence energy consumption involved in this estimation of the second amount.

Problems solved by technology

However, the conventional exhaust air purifiers for internal combustion engines suffer from the problems described below.

This makes it difficult to accurately estimate the amount of accumulated particulate matter based on pressure difference alone.

This consumes energy each time an amount of accumulated particulate matter is estimated.

Accordingly, frequent estimation of the amount of accumulated particulate matter increases energy consumption.

Images