Exhaust gas control system for internal combustion engine

An exhaust gas control system for an internal combustion engine, the exhaust gas control system comprising:

• a filter arranged in an exhaust passage of the internal combustion engine, the filter being configured to collect particulate matter that is emitted from the internal combustion engine;
• a differential pressure sensor configured to detect an upstream-downstream differential pressure that is a difference between an exhaust pressure upstream of the filter and an exhaust pressure downstream of the filter;
• and
• an electronic control unit configured to
• i) acquire a particulate matter accumulation amount that is an amount of particulate matter collected in the filter,
• ii) execute a filter regeneration process, the filter regeneration process being a process of, when the particulate matter accumulation amount is larger than or equal to a predetermined threshold, oxidizing and removing particulate matter collected in the filter by raising a temperature of the filter to a first target temperature,
• iii) execute a pre-regeneration process for a predetermined period and execute the filter regeneration process after completion of the pre-regeneration process, the pre-regeneration process being a process of, when the particulate matter accumulation amount becomes larger than or equal to the predetermined threshold, raising the temperature of the filter to a second target temperature lower than the first target temperature and increasing the concentration of nitrogen dioxide contained in exhaust gas flowing into the filter, and
• iv) set the first target temperature and execute the filter regeneration process such that the first target temperature in the case where a speed of change in a detected value of the differential pressure sensor during execution of the pre-regeneration process is a first speed is lower than the first target temperature in the case where the speed of change is a second speed, the first speed being higher than the second speed.