Exhaust purifier of an internal combustion engine

An exhaust purifier for purifying an exhaust gas of an internal combustion engine used in an exhaust purification system that has an addition unit and a catalyst, wherein the addition unit, disposed in an exhaust pipe of the exhaust purification system, adds a predetermined additive agent to the exhaust pipe, and the catalyst, disposed on a downstream side of the addition unit in the exhaust pipe, purifies the exhaust gas with the additive agent added by the addition unit and stored therein, the exhaust purifier comprising:

• an addition amount determination unit determining a total amount of the additive agent to add from the addition unit;
• an addition control unit controlling the addition unit to enable the additive agent to be added to the exhaust pipe by the total amount determined by the addition amount determination unit;
• and
• a flow velocity calculation unit calculating an exhaust flow velocity of the exhaust gas, wherein
• the addition control unit controls the addition unit to decrease a per-unit-time addition amount of the additive agent as the exhaust flow velocity calculated by the flow velocity calculation unit decreases.