EXHAUST PURIFICATION DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

A reduction in the accuracy of a failure determination of a filter due to a reduction in the detection accuracy of a PM sensor is suppressed. In order to achieve this, provision is made for 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, a PM sensor for detecting an amount of particulate matter in an exhaust gas at the downstream side of the NOx selective reduction catalyst, and a supply decrease part that 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, wherein the conditions include: a condition in which the temperature of the NOx selective reduction catalyst is equal to or less than a threshold value; a condition in which the temperature of the exhaust gas is equal to or less than a threshold value; a condition in which the flow rate of the exhaust gas is equal to or larger than a threshold value; and a condition in which the amount of adsorption of the reducing agent in the NOx selective reduction catalyst is equal to or larger than a threshold value.