Exhaust gas purification apparatus for an internal combustion engine

摘要

An exhaust gas purification apparatus including a filter, an NOx selective reduction catalyst at the downstream side of the filter, a supply device for supplying a reducing agent to the NOx selective reduction catalyst, and a PM sensor for detecting an amount of particulate matter in an exhaust gas at the downstream side of the NOx selective reduction catalyst. A supply decrease part makes an amount of supply of the reducing agent smaller in cases where at least one of several conditions is satisfied.

主权项

1. An exhaust gas purification apparatus for an internal combustion engine comprising:
a filter that is arranged in an exhaust passage of the internal combustion engine for trapping particulate matter contained in an exhaust gas; an NOx selective reduction catalyst that is arranged at the downstream side of said filter and reduces NOx by means of a reducing agent which is supplied thereto; a supply device that supplies the reducing agent to said NOx selective reduction catalyst from the upstream side of said NOx selective reduction catalyst; a particulate matter (PM) sensor that detects an amount of the particulate matter in the exhaust gas at the downstream side of said NOx selective reduction catalyst, wherein the reducing agent and the particulate matter influence changes in the detected amount of the PM sensor; and a controller having control logic which, makes an amount of supply of the reducing agent smaller in cases where at least one of the following conditions is satisfied than in cases where any of the conditions is not satisfied to suppress a reduction in accuracy of the PM sensor during a period when the particulate matter is trapped by the PM sensor, wherein the conditions include: a condition in which the temperature of said NOx selective reduction catalyst is equal to or less than a threshold value; and a condition in which the temperature of the exhaust gas is equal to or less than a threshold value; and a condition in which the flow rate of the exhaust gas is equal to or larger than a threshold value.