Patent ID: 8375703

Claim:
An exhaust gas purification device comprising: an exhaust gas passage having a return portion; a reducing agent supply portion which is arranged in the return portion or in an upstream side exhaust gas passage disposed on an upstream side of the return portion, the reducing agent supply portion supplying a reducing agent into the exhaust gas passage; a reduction catalyst which is arranged in a downstream side exhaust gas passage disposed on a downstream side of the return portion and which reduces and purifies nitrogen oxide using the reducing agent; and a housing having a main body in which the upstream side exhaust gas passage and the downstream side exhaust gas passage are housed, and a cap which is attached to a first surface of the main body that is provided with an outlet side opening of the upstream side exhaust gas passage and an inlet side opening of the downstream side exhaust gas passage, and the return portion being formed by a space surrounded by the main body and the cap, wherein at least one of the first surface of the main body and a second surface in the cap which faces the first surface is provided with a guide portion for guiding an exhaust gas flow, the guide portion being arranged in a direction intersecting with the first surface and the second surface, and is provided with a reducing agent diffusion portion for facilitating mixing of the reducing agent with the exhaust gas, the reducing agent diffusion portion being arranged in a middle region of the flow of the exhaust gas guided by the guide portion, the guide portion includes a first ring-shaped member having opening portions, a second ring-shaped member having an opening portion, first guide plates and second guide plates, and the first ring-shaped member is directly connected to the outlet side opening of the upstream side exhaust gas passage and the second ring-shaped member is directly connected to the inlet side opening of the downstream side exhaust gas passage, and the first guide plates guide the exhaust gas flow poured out from the opening portions of the first ring-shaped member to the reducing agent diffusion portion, and the second guide plates guide the exhaust gas flow passing through the reducing agent diffusion portion to the opening portion of the second ring-shaped member.