Patent ID: 8341941

Claim:
An internal combustion engine exhaust purification device, comprising: an NO x selective reduction catalyst, a urea feed device, an NO x storage catalyst, an engine exhaust passage, and an electronic control unit, wherein the NO x storage catalyst and the NO x selective reduction catalyst are inside the engine exhaust passage and the NO x storage catalyst is upstream of the NO x selective reduction catalyst, wherein the NO x storage catalyst stores NO x present in an exhaust gas passing through the engine exhaust passage and releases stored NO x responsive to temperature, wherein the electronic control unit includes operative logic configured to (i) calculate an amount of NO x stored in the NO x storage catalyst and an amount of NO x released from the NO x storage catalyst, (ii) calculate an amount of the NO x in the exhaust gas passing from the NO x storage catalyst into the NO x selective reduction catalyst by subtracting the calculated stored NO x amount from an amount of the NO x in the engine exhaust upstream from the NO x storage catalyst and by adding the calculated released NO x amount to the NO x amount in the engine exhaust upstream from the NO x storage catalyst, (iii) forcibly raise a temperature of the NO x storage catalyst to cause the NO x storage catalyst to release stored NO x when a calculated stored NO x amount exceeds a predetermined allowable value, and (iv) feed an amount of urea necessary to reduce the NO x flowing into the NO x selective reduction catalyst.