Exhaust purification system of internal combustion engine

An exhaust purification system of an internal combustion engine, comprising:

• an air/fuel ratio sensor that is provided in an exhaust passage of the internal combustion engine, and generates a signal according to the air/fuel ratio of exhaust gas;
• an upstream catalytic converter that is provided on a downstream side of a detection location of the air/fuel ratio sensor in the exhaust passage, and has a catalyst for purifying the exhaust gas;
• a downstream filter that is provided on a downstream side of the upstream catalytic converter in the exhaust passage, and purifies by capturing particulate matter in the exhaust gas;
• and
• a controller that drives fuel injectors provided to the internal combustion engine so that an output signal of the air/fuel ratio sensor converges to a predetermined target value,
• wherein the downstream filter includes:
• a filter substrate in which a plurality of cells extending from an inlet-side end face until an outlet-side end face of exhaust gas are formed to be divided by porous barrier walls, and an opening at the inlet-side end face and an opening at the outlet-side end face of the cells are alternately sealed;
• and a downstream three-way catalyst that is loaded on the barrier walls,
• wherein the downstream three-way catalyst contains a catalytic metal including at least Rh, and an Oxygen storage capacity (OSC) material having oxygen occlusion/release ability,
• wherein the OSC material of the downstream three-way catalyst contains a complex oxide having Nd and Pr in the crystalline structure thereof,
• wherein the upstream catalytic converter includes a honeycomb substrate in which a plurality of cells extending from an inlet-side end face to an outlet-side end face of exhaust gas is formed to be divided by porous barrier walls, and an upstream three-way catalyst loaded on the barrier walls of the honeycomb substrate,
• wherein the upstream three-way catalyst contains a catalytic metal and an OSC material having oxygen occlusion/release ability, and
• wherein the content of OSC material per unit volume of the filter substrate is less than the content of OSC material per unit volume of the honeycomb substrate.