| 摘要 |
Disclosed is an internal combustion exhaust emission control device that can control the adhesion of HC onto the EGR passage, etc., as the exhaust air-fuel ratio becomes richer. An exhaust emission control device is equipped with a high-pressure EGR passage (6), through which some of the exhaust upstream of a turbine (81) flows back into an air intake manifold (3), a high-pressure EGR controller (43), a low-pressure EGR passage (10), through which some of the exhaust downstream from the turbine (81) flows back into an air intake tube (2), a low-pressure EGR controller (44), an NOx purifying catalyst (31), which is disposed inside an exhaust pipe (4) downstream from the exhaust outlet in the low-pressure EGR passage (10), and captures NOx in an oxygen atmosphere and purifies the captured NOx with a reducing atmosphere, an NOx purification catalyst reduction controller (41), which controls the air-fuel ratio of the exhaust gas by means of reduction, and an EGR switch (45), which, when reduction control is executed, selects for the low-pressure EGR controller (44) to regulate circulation when the exhaust air-fuel ratio is at or over a specified threshold, and selects exhaust circulation control by the high-pressure EGR controller (43) when the ratio is below the aforementioned threshold. |
