Patent ID: 8091338
Filing Date: 2012-01-10
Classification: F01N,F02B,F02D,F02M,Y02T

Abstract:
1. An exhaust gas cleaning apparatus for cleaning exhaust gas from an internal combustion engine, the apparatus comprising: a Lean NO a fuel adding device located upstream of the LNT to add fuel to the exhaust gas for making the exhaust gas rich; an exhaust gas returning passage that branches off from the exhaust gas passage at a position downstream of a turbocharger of the engine to return part of the exhaust gas to an intake air passage of the engine; and a controller configured to determine an operating condition of the engine and control the exhaust gas cleaning apparatus to selectively operate in one of first and second operation modes according to the determined operating condition of the engine, in the first operation mode the fuel adding device adding the fuel to the exhaust gas with the exhaust gas returning passage closed, in the second operation mode the part of the exhaust gas being returned to the intake air passage through the exhaust gas returning passage without the fuel being added by the fuel adding device to the exhaust gas, wherein the controller is configured to determine whether the engine operates in a first operation region, in which both the rotational speed and load of the engine is low, or in a second operation region in which either or both of the rotational speed and load of the engine are high, and the controller is configured to control the exhaust gas cleaning apparatus to operate in the first operation mode when the engine operates in the first operation region and in the second operation mode when the engine operates in the second operation region.