Catalyst device

Abstract

A catalyst device (30) for purifying exhaust gas (G) by passing the exhaust gas (G) through a honeycomb core (31, 31a, 31b, 31c, 31d) includes: the honeycomb core (31, 31a, 31b, 31c, 31d) including a metallic foil (40) supporting a catalyst and wound. A portion of the metallic foil (40) has a plurality of through holes (H). The honeycomb core (31, 31a, 31b, 31c, 31d) has a dense region (A) where the through holes (H) are densely formed, a zero region (B) where no through hole (H) is formed, and a boundary region (C) between the dense region (A) and the zero region (B) in an axial direction in which the exhaust gas (G) flows. The boundary region (C) is configured such that a total area of the through holes (H) in the boundary region (C) decreases gradually from near the dense region (A) toward the zero region (B).

What is claimed is: 
     
         1 . A catalyst device ( 30 ) for purifying exhaust gas (G) by passing the exhaust gas (G) through a honeycomb core ( 31 ,  31   a ,  31   b ,  31   c ,  31   d ), the catalyst device ( 30 ) comprising: the honeycomb core ( 31 ,  31   a ,  31   b ,  31   c ,  31   d ) including a metallic foil ( 40 ) supporting a catalyst and wound,
 a portion of the metallic foil ( 40 ) having a plurality of through holes (H),   the honeycomb core ( 31 ,  31   a ,  31   b ,  31   c ,  31   d ) having   a dense region (A) where the through holes (H) are densely formed, a zero region (B) where no through hole (H) is formed, and a boundary region (C) between the dense region (A) and the zero region (B) in an axial direction in which the exhaust gas (G) flows,   the boundary region (C) being configured such that a total area of the through holes (H) in the boundary region (C) decreases gradually from near the dense region (A) toward the zero region (B).   
     
     
         2 . The catalyst device according to  claim 1 , wherein
 the boundary region (C) is only downstream of the dense region (A) along a flow of the exhaust gas (G).   
     
     
         3 . The catalyst device according to  claim 1 , wherein
 the boundary region (C) is configured such that a total area of the through holes (H) in the boundary region (C) decrease gradually due to a reduction in the number of the through holes (H) in the boundary region (C).   
     
     
         4 . The catalyst device according to  claim 1 , wherein
 in the dense region (A), the through holes (H) have an identical diameter, and are equally spaced apart from each other, and   the boundary region (C) is configured such that while a layout of the through holes (H) in the dense region (A) is maintained, a total area of the through holes (H) in the boundary region (C) decreases gradually due to a gradual reduction in a diameter of the through holes (H) in the boundary region (C).   
     
     
         5 . The catalyst device according to  claim 3 , wherein
 in the dense region (A), the through holes (H) have an identical diameter, and are equally spaced apart from each other,   the boundary region (C) is configured such that while a layout of the through holes (H) in the dense region (A) is maintained, the total area of the through holes (H) in the boundary region (C) decreases gradually due to a reduction in the number of the through holes (H) in the boundary region (C), and   the through holes (H) are not formed around at least one of the through holes (H) closest to the zero region (B).   
     
     
         6 . The catalyst device according to  claim 1 , wherein
 the boundary region (C) comprises a plurality of boundary regions (C) both upstream and downstream of the dense region (A) along a flow of the exhaust gas (G).