Particulate filter
According to the present invention, a wall-flow type particulate filter in which pressure loss is suppressed despite a large formation region of a catalyst layer is provided. The particulate filter disclosed herein includes a wall-flow type base material and a catalyst layer formed on the base material. The base material includes an inlet side cell whose only end part on an exhaust gas entry side is open, an outlet side cell whose only end part on an exhaust gas exit side is open, and a partition wall that sections between the inlet side cell and the outlet side cell and includes a plurality of pores communicating between the inlet side cell and the outlet side cell. A first catalyst layer is formed on a surface of the partition wall that is in contact with the inlet side cell. The first catalyst layer is provided in a region over 80% of a total length of the base material from an end part of the base material on the exhaust gas entry side toward an end part thereof on the exhaust gas exit side. In at least a region from a position corresponding to 20% of the total length of the base material to a position corresponding to 80% thereof, from the end part of the base material on the exhaust gas entry side, the first catalyst layer is inclined so that a thickness of the first catalyst layer decreases from the end part on the exhaust gas entry side toward the end part on the exhaust gas exit side.
1 . A particulate filter comprising a wall-flow type base material and a catalyst layer formed on the base material, wherein
the base material includes an inlet side cell whose only end part on an exhaust gas entry side is open, an outlet side cell whose only end part on an exhaust gas exit side is open, and a partition wall that sections between the inlet side cell and the outlet side cell and includes a plurality of pores communicating between the inlet side cell and the outlet side cell,
a first catalyst layer is formed on a surface of the partition wall that is in contact with the inlet side cell,
the first catalyst layer is provided in a region over 80% of a total length of the base material from an end part of the base material on the exhaust gas entry side toward an end part thereof on the exhaust gas exit side,
in at least a region from a position corresponding to 20% of the total length of the base material to a position corresponding to 80% thereof, from the end part of the base material on the exhaust gas entry side, the first catalyst layer is inclined so that a thickness of the first catalyst layer decreases from the end part on the exhaust gas entry side toward the end part on the exhaust gas exit side,
a second catalyst layer is formed on a wall surface of the pore in a predetermined region from a surface of the partition wall that is in contact with the outlet side cell toward the inlet side cell, and
a catalyst non-formation region where the catalyst layer is not formed substantially is provided between the first catalyst layer and a formation region of the second catalyst layer in a thickness direction of the partition wall.
2 . The particulate filter according to claim 1 , wherein a ratio (D20/D80) of a thickness (D20) of the first catalyst layer at the position corresponding to 20% of the total length of the base material from the end part of the base material on the exhaust gas entry side to a thickness (D80) of the catalyst layer at the position corresponding to 80% of the total length of the base material from the end part of the base material on the exhaust gas entry side is 2 or more and 4 or less.
3 . The particulate filter according to claim 1 , wherein the thickness (D80) of the first catalyst layer at the position corresponding to 80% of the total length of the base material from the end part of the base material on the exhaust gas entry side is 11 μm or more and 25 μm or less.
4 . The particulate filter according to claim 1 , wherein the first and second catalyst layers contain a three-way catalyst that oxidizes CO and HC and reduces NOx, and a carrier that carries the three-way catalyst.
5 . The particulate filter according to claim 4 , wherein the three-way catalyst contains at least one kind selected from the group consisting of Pt, Pd, and Rh.