| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide technology enabling more suitable NOx reduction process in an exhaust emission control device supplying NOx catalyst with hydrogen formed by hydrogen forming catalyst as a reducer. <P>SOLUTION: This device is provided with a storage reduction type NOx catalyst, the hydrogen forming catalyst arranged in an upstream of the NOx catalyst and forming hydrogen from carbon monoxide and hydrocarbon in exhaust gas, and a rich spike means making air fuel ratio of exhaust gas flowing in the hydrogen forming catalyst temporarily rich. Temperature of the hydrogen forming catalyst is dropped to execute deep rich spike if temperature T<SB>CTA</SB>of the hydrogen forming catalyst is lower than a first reference temperature T<SB>1</SB>, temperature of the hydrogen forming catalyst is raised to execute deep rich spike if the temperature is between the first reference temperature T<SB>1</SB>and a second reference temperature T<SB>2</SB>, and shallow rich spike is executed if the temperature is higher than the second reference temperature T<SB>2</SB>in execution of reduction process reducing NOx stored in the NOx catalyst. The hydrogen forming catalyst has double layer coating of platinum layer and rhodium layer, and minor ceria is contained in part of the rhodium layer. <P>COPYRIGHT: (C)2008,JPO&INPIT |
