Exhaust purification apparatus

An exhaust purification apparatus, comprising:

• an exhaust manifold;
• a cylindrical catalytic converter;
• and
• a connection portion that connects the exhaust manifold to the catalytic converter, wherein
• the exhaust purification apparatus is configured such that exhaust gas that has flowed from the exhaust manifold into the connection portion is directed to the catalytic converter,
• the connection portion includes:
• a tubular diffusion portion to which the exhaust manifold is connected;
• and
• a coupling portion that couples the diffusion portion to the catalytic converter,
• the diffusion portion is arranged such that a central axis of the diffusion portion aligns with a central axis of the catalytic converter,
• the coupling portion is configured such that a cross-sectional area of a passage of the coupling portion increases from a connection point with the diffusion portion toward a connection point with the catalytic converter,
• a side surface of the diffusion portion includes:
• a connection surface to which the exhaust manifold is connected;
• a collision surface arranged such that a central axis of the diffusion portion is positioned between the collision surface and the connection surface, wherein exhaust gas that has flowed from the exhaust manifold into the diffusion portion collides with the collision surface;
• a first coupling surface that couples an upper end of the connection surface to an upper end of the collision surface;
• and
• a second coupling surface that couples a lower end of the connection surface to a lower end of the collision surface, and
• cross-sectional shapes of the first coupling surface, the second coupling surface, and the collision surface along a plane orthogonal to the central axis of the diffusion portion are arcuate, wherein a curvature of the cross-sectional shape of the collision surface is smaller than curvatures of the cross-sectional shapes of the first coupling surface and the second coupling surface.