| 摘要 |
PROBLEM TO BE SOLVED: To improve exhaust gas purification performance effectively using heat of exhaust gas by reducing heat capacity of a whole catalyst by decreasing total cross section of an exhaust gas flowing passage of an upstream catalyst as compared with a downstream catalyst, of the two catalysts arranged upstream and downstream of an exhaust passage. SOLUTION: In a catalyst device 2 connected with an exhaust pipe of an engine of an automobile, both catalysts 4, 5 respectively accommodated upstream and downstream of a catalyst container 3 are monolithic type, the diameter of the upstream catalyst 4 is shorter than that of the downstream catalyst 5 corresponding to the diameter of the catalyst container 3, and the length of the upstream catalyst 4 is shorter than that of the downstream catalyst 5. A clearance 6 of 5-50 mm is formed between the both catalysts 4, 5. Therefore, exhaust gas contact area per unit capacity for the upstream catalyst 4 becomes larger than that of the downstream catalyst 5, and mass per unit capacity is reduced, and therefore, the upstream catalyst 4 rapidly increases in temperature to provide activation, and this catalyst reaction heat can accomplish early activation of the downstream catalyst 5. |
