초록 ▼

A NOx occluding member that occludes NOx when the air-fuel ratio is on the fuel-lean side is disposed in an engine exhaust passage. An NOx ammonia sensor is disposed in the engine exhaust passage downstream of the NOx occluding member. A surplus amount of a reducing agent that is not used to release

A NOx occluding member that occludes NOx when the air-fuel ratio is on the fuel-lean side is disposed in an engine exhaust passage. An NOx ammonia sensor is disposed in the engine exhaust passage downstream of the NOx occluding member. A surplus amount of a reducing agent that is not used to release NOx is determined from a change in the ammonia concentration detected by the NOx ammonia sensor when the air-fuel ratio is changed to the fuel-rich side so as to release the NOx from the NOx occluding member.

대표청구항 ▼

A NOx occluding member that occludes NOx when the air-fuel ratio is on the fuel-lean side is disposed in an engine exhaust passage. An NOx ammonia sensor is disposed in the engine exhaust passage downstream of the NOx occluding member. A surplus amount of a reducing agent that is not used to release

A NOx occluding member that occludes NOx when the air-fuel ratio is on the fuel-lean side is disposed in an engine exhaust passage. An NOx ammonia sensor is disposed in the engine exhaust passage downstream of the NOx occluding member. A surplus amount of a reducing agent that is not used to release NOx is determined from a change in the ammonia concentration detected by the NOx ammonia sensor when the air-fuel ratio is changed to the fuel-rich side so as to release the NOx from the NOx occluding member. orresponding with the negatively curved contour of the overlay tabs. 6. The laminated shingle according to claim 1 wherein the front surface of the underlay member includes a shading area extending in a generally straight line, wherein the second curved contour exposes a portion of the shading area. 7. The laminated shingle according to claim 6, wherein the shading area comprises a different color or hue than a remainder of the front surface of the underlay. 8. The laminated shingle according to claim 7, wherein the shading area comprises a darker color or hue. 9. The laminated shingle according to claim 1 wherein the front surface of the overlay member includes a shading area extending in a generally straight line adjacent to the second curved contour. 10. The laminated shingle according to claim 9, wherein the shading area comprises a different color or hue than a remainder of the front surface of the overlay. 11. The laminated shingle according to claim 10, wherein the shading area comprises a darker color or hue. 12. The laminated shingle according to claim 9, wherein when the laminated shingles are laid in courses on a roof, when a subsequent shingle is positioned above a previous shingle, the first generally curved contour exposes a portion of the shading area of the previous shingle. 13. The laminated shingle according to claim 1, wherein the underlay member comprises an underlay lower edge underlaying the overlay lower edge, wherein the underlay lower edge comprises a third generally curved contour, said third contour substantially corresponding to, and aligned with, the first curved contour of the overlay. 14. A composite, laminated shingle, comprising: an overlay member having front and rear surfaces, the overlay member including a headlap portion and a butt portion, the headlap portion including a lower portion of a first curved contour, the butt portion including a plurality of tabs separated by cutouts, each tab extending in length from the lower portion of the headlap portion to a lower edge defining a butt edge of the shingle, the lower edge of each tab having a second generally curved contour, said second curved contour being inverted from the first curved contour; and an underlay member having a front surface fixedly attached to the rear surface of the overlay member, the underlay member including an underlay lower edge, a portion of the underlay lower edge having a generally curved contour corresponding to the lower edge of each tab and exposed portions extending between the tabs of the overlay member in the cutouts that separate the tabs, a lower edge of the exposed portions defining a portion of the butt edge of the shingle having a substantially straight contour, wherein the shingle operates to optically simulate the three dimensional ridges and valleys of a tiled roof when laid on a roof with other substantially identically shaped shingles in overlapping longitudinal courses in a predetermined assembly in which the tabs and cutouts of the substantially identically shaped shingles in each course are vertically aligned with the respective tabs and cutouts of the shingles in the next lower course of shingles, wherein the portion of the butt edge of the shingle defined by the lower edge of each tab of the overlay member and the portion of the lower edge of the underlay member has a negatively curved contour, and the underlay member further including a layer of granules on the front surface forming a shading area, the exposed portions of the underlay member comprising at least a portion of the shading area. 15. The laminated shingle according to claim 14, wherein the shading area comprises a different color or hue than a remainder of the front surface. 16. The laminated shingle according to claim 14, wherein the shading area comprises a darker color or hue. 17. A composite, laminated shingle, comprising: an overlay member having front and rear surfaces, the overlay member including a headlap portion and a butt portion, the headlap portion including a lower portion of a first curved contour, the butt portion including a plurality of tabs separated by cutouts, each tab extending in length from the lower portion of the headlap portion to a lower edge defining a butt edge of the shingle, the lower edge of each tab having a second generally curved contour, said second curved contour being inverted from the first curved contour; and an underlay member having a front surface fixedly attached to the rear surface of the overlay member, the underlay member including an underlay lower edge, the underlay lower edge comprising a generally straight line below the lowermost portion of the second contour, wherein the shingle operates to optically simulate the three dimensional ridges and valleys of a tiled roof when laid on a roof with other substantially identically shaped shingles in overlapping longitudinal courses in a predetermined assembly in which the tabs and cutouts of the substantially identically shaped shingles in each course are vertically aligned with the respective tabs and cutouts of the shingles in the next lower course of shingles, wherein the portion of the butt edge of the shingle defined by the lower edge of each tab of the overlay has a negatively curved contour, and the underlay member further including a layer of granules on the front surface forming a shading area. 18. The laminated shingle according to claim 17, wherein the shading area comprises a different color or hue than a remainder of the front surface. 19. A roof covering including a plurality of successive generally horizontal courses of laminated shingles, the shingles in each course being laid in a side-by-side relationship and horizontally offset from the shingles in adjacent courses, each laminated shingle comprising: an overlay member having front and rear surfaces, the overlay member including a headlap portion and a butt portion, the headlap portion including a lower boundary portion of a first generally curved contour, the butt portion including a plurality of tabs separated by cutouts, each tab extending in length from the lower boundary of the headlap portion to an overlay lower edge defining a butt edge of the shingle, the lower edge of each tab having a second generally curved contour inverted from the first curved contour; and an underlay member having a front surface fixedly attached to the rear surface of the overlay member, the underlay including an underlay lower edge, the underlay member including a layer of granules on the front surface forming a first shading area, the underlay lower edge extending to the lower edge of each tab and exposed portions extending between the tabs of said overlay member in the cutouts that separate the tabs to expose at least a portion of the first shading area, the lower edge of the exposed portions defining a portion of the butt edge of the shingle having a substantially straight contour, wherein the shingle operates to optically simulate the three dimensional ridges and valleys of a tiled roof when laid on a roof with other substantially identically shaped shingles in overlapping longitudinal courses in a predetermined assembly in which one of the tabs and cutouts of the substantially identically shaped shingles in each course are vertically aligned with each other. 20. The roof covering according to claim 19, wherein the headlap portion of the overlay member includes a layer of granules on the front surface forming a second shading area. 21. The roof covering according to claim 19, wherein the shingles in overlapping longitudinal courses are longitudinally offset from the next lower course of shingles by a distance that is approximately one-fourth of the width of the shingles. 22. The laminated shingle according to claim 20, wherein the first and second shading areas comprise a different color or hue than a remainder of the front surface of the underlay and overlay. 23. A laminated shingle,