Exhaust gas purification device

1. An exhaust gas purification device for purifying exhaust gas flowing through an exhaust gas channel of an engine, the exhaust gas purification device comprising:

fins installed in a cylindrical wall portion of the exhaust gas channel to guide the exhaust gas to generate a swirling flow; and

an injection device including a nozzle which injects a reducing agent to the swirling flow of the exhaust gas,

wherein an injection region of the reducing agent presents a conical shape with the injection device as a vertex thereof,

wherein the fins are expanded and opened from a first end closer to the injection device toward a second end in a downstream side of an injection direction of the reducing agent so as to surround the injection region of the reducing agent in the injection direction of the reducing agent, a distance between the fins at the first end in a direction parallel to a diameter of the cylindrical wall portion being less than a distance between the fins at the second end in the direction parallel to the diameter of the cylindrical wall portion,

wherein an axis of the injection region and an axis of the cylindrical wall portion both are parallel with the injection direction of the reducing agent,

wherein a gap exists between the injection region and the fins along an entire length of the fins in a region where the fins surround the injection region, and

wherein the fins lie entirely outside of the injection region.

2. The exhaust gas purification device according to claim 1 , wherein the cylindrical wall portion bounds the injection region,

inlets through which the exhaust gas is introduced to an inside of the cylindrical wall portion are formed at the cylindrical wall portion, and

the fins are formed in the inlets while extending to the inside of the cylindrical wall portion.

3. The exhaust gas purification device according to claim 2 , wherein a plurality of inlets are formed, and

the fins are formed in the plurality of inlets, respectively.

4. The exhaust gas purification device according to claim 1 , wherein each of the fins has a sectional surface curved toward the injection region when viewed from the injection direction of the reducing agent, and a degree of curvature of said sectional surface decreases as said sectional surface goes toward the downstream side of the injection direction of the reducing agent.

5. The exhaust gas purification device according to claim 2 , wherein each of the fins has a sectional surface curved toward the injection region when viewed from the injection direction of the reducing agent, and a degree of curvature of said sectional surface decreases as said sectional surface goes toward the downstream side of the injection direction of the reducing agent.

6. The exhaust gas purification device according to claim 3 , wherein each of the fins has a sectional surface curved toward the injection region when viewed from the injection direction of the reducing agent, and a degree of curvature of said sectional surface decreases as said sectional surface goes toward the downstream side of the injection direction of the reducing agent.

7. The exhaust gas purification device according to claim 1 , further comprising a first casing including a particulate filter,

wherein an upstream end of the cylindrical wall portion is inserted into a downstream side of the particulate filter in the first casing, a direction of the exhaust gas flowing in the first casing being perpendicular to a direction of the exhaust gas flowing in the cylindrical wall portion.

8. The exhaust gas purification device according to claim 7 , further comprising a second casing including a selective catalytic reduction catalyst,

wherein a downstream end of the cylindrical wall portion is in fluid communication an upstream side of the selective catalytic reduction catalyst in the second casing, a direction of exhaust flowing in the second casing being perpendicular to the direction of the exhaust gas flowing in the cylindrical wall portion and being parallel to the direction of the exhaust gas flowing in the first casing.

9. The exhaust gas purification device according to claim 7 , further comprising an oxidation catalyst disposed upstream of the particulate filter.