Exhaust gas purification system for an internal combustion engine

摘要

The present invention discloses an exhaust gas purification system for an internal combustion engine, which is provided with: a low pressure EGR mechanism that is equipped with a low pressure EGR passage and a low pressure EGR valve; a selective reduction type catalyst that is arranged in a portion of the exhaust passage downstream; a supply device which serves to supply an ammonia derived compound to said selective reduction type catalyst; and a control unit that causes said supply device to supply the ammonia derived compound when said low pressure EGR valve is in a valve open state, makes the amount of the ammonia derived compound supplied from said supply device larger in cases where an amount of the low pressure EGR gas flowing through said low pressure EGR passage is large, in comparison with the case where it is small.

主权项

1. An exhaust gas purification system for an internal combustion engine comprising:
a low pressure EGR mechanism that is equipped with a low pressure EGR passage which serves to introduce a part of an exhaust gas flowing through a portion of the exhaust passage downstream of a turbine of a centrifugal supercharger to a portion of an intake passage upstream of a compressor as a low pressure EGR gas, and a low pressure EGR valve which serves to change a channel cross section of said low pressure EGR passage; a selective reduction type catalyst that is arranged in-a portion of the exhaust passage downstream of a connection portion of said low pressure EGR passage; a supply device which serves to supply an ammonia derived compound to said selective reduction type catalyst, and is arranged in such a manner that the ammonia derived compound is able to be supplied into the exhaust passage at a location upstream of the connection portion of said low pressure EGR passage; and a control unit that:causes said supply device to supply the ammonia derived compound therefrom when said low pressure EGR valve is in a valve open state, makes the amount of the ammonia derived compound supplied from said supply device larger in cases where an amount of the low pressure EGR gas flowing through said low pressure EGR passage is large, in comparison with the case where it is small.