Patent ID: 8555621

Claim:
An exhaust gas purification device for an internal combustion engine having an exhaust gas passage, comprising: a NOx storing and reducing catalyst that is disposed in the exhaust gas passage and that stores NOx contained in inflow exhaust gas when an air-fuel ratio of the inflow exhaust gas is lean and releases and reduces the stored NOx when the air-fuel ratio of the inflow exhaust gas becomes rich; a stored NOx amount calculator for calculating a stored NOx amount of the NOx storing and reducing catalyst; and a controller for controlling an exhaust gas purification operation based on said calculated stored NOx amount, wherein: when the air-fuel ratio of the inflow exhaust gas is lean, ratios of NOx components, which are ratios of amounts of NOx components to the total amount of NOx in said inflow exhaust gas, are calculated, and an increment of the stored NOx amount per unit time is calculated based on said calculated ratios of NOx components.