Exhaust gas purification device

1. An exhaust gas purification device comprising:

a spray nozzle provided in an exhaust pipe of an engine;

a mixer provided downstream of the spray nozzle in a flow direction of exhaust gas; and

a catalyst reactor provided downstream of the mixer,

the exhaust gas purification device being configured to spray a reducing agent from the spray nozzle to the exhaust gas from the engine, to mix the reducing agent with the exhaust gas in the mixer, and to reduce one or more nitrogen oxides in the exhaust gas using a catalyst contained in the catalyst reactor, wherein:

the mixer includes a cylindrical body, a plurality of fins arranged in the cylindrical body radially outward with respect to an axis of the cylindrical body, and a support member welded to downstream-facing surfaces of the fins and configured to support the fins; and

an upstream portion of each fin that is at its upstream side in the flow direction of the exhaust gas is shaped to provide a cutoff portion formed by cutting the fin from an upstream side end portion of the fin toward the axis and toward a downstream side of the fin.

2. The exhaust gas purification device according to claim 1 , wherein, when the mixer is viewed from its upstream side, the cutoff portion of each fin is positioned so as to overlap its adjacent fin out of the plurality of fins.

3. The exhaust gas purification device according to claim 1 , wherein

the support member is formed by one or more shaped steel members each having a V cross-sectional shape or a circular cross-sectional shape.

4. The exhaust gas purification device according to claim 3 , wherein the support member includes:

the one or more shaped steel members, the number of which is two or more and which cross each other at an intersection portion positioned at the axis of the cylindrical body; and

a reinforcing plate welded to the intersection portion.