DIESEL ENGINE EXHAUST GAS POST-PROCESSING SYSTEM AND EXHAUST GAS POST-PROCESSING METHOD

摘要

A diesel engine exhaust gas post-processing system which executes a first operation in which EGR gas is not introduced into an intake passage, and a second operation in which EGR gas is introduced into the intake passage and the amount of intake air is reduced compared with the first operation, said system including: a switching timing determination unit for determining whether or not a given timing is the timing for switching from the first operation to the second operation, when the temperature inside a collector or the temperature at a compression end is less than the temperature at the boundary of a misfire region which is preset during the second operation; a temperature raising unit for raising the temperature inside the collector or the temperature at the compression end when said timing is the switching timing; and an intake air amount reduction suppression unit for suppressing reductions in the amount of intake air when said timing is likewise the switching timing.