Patent ID: 7484360

Claim:
A method for recovering a filter of an exhaust gas control system for an internal combustion engine, which includes a filter for capturing particulate matter in exhaust gas discharged from an internal combustion engine, the filter being provided in an exhaust passage for the internal combustion engine; a filter forced recovery portion that performs a recovery process that removes the particulate matter captured by the filter by forcibly oxidizing the particulate matter so as to recover a capturing ability of the filter; and a deposited amount detection portion that detects an amount of the particulate matter captured by the filter and deposited in the filter, and in which an entire range of an engine operating state decided by a rotational speed and torque of the internal combustion engine includes a first operating state range where a temperature of the exhaust gas discharged from the internal combustion engine is low, and the particulate matter captured by the filter is not oxidized and an amount of the particulate matter deposited in the filter increases if a recovery process is not performed, and a second operating state range where the temperature of the exhaust gas discharged from the internal combustion engine is high, and the particulate matter captured by the filter is oxidized and the amount of the particulate matter deposited in the filter decreases even if the recovery process is not performed, the method comprising the steps of: detecting the amount of the particulate matter deposited in the filter using the deposited amount detection portion in a case where the operating state of the internal combustion engine belongs to the first operating state range; performing the recovery process using the filter forced recovery portion when the detected amount of the particulate matter deposited in the filter becomes equal to or larger than a predetermined amount in the case where the operating state of the internal combustion engine belongs to the first operating state range; and performing the recovery process using the filter forced recovery portion based on a continuous belonging time period during which the operating state of the internal combustion engine continues to belong to the second operating state range in a case where the operating state of the internal combustion engine belongs to the second operating state range; wherein the recovery process is performed when the continuous belonging time period during which the operating state of the internal combustion engine continues to belong to the second operating state range becomes equal to or longer than a predetermined time period in a case where the operating state of the internal combustion engine belongs to the second operating state range.