Engine exhaust structure

Abstract

The present invention provides an engine exhaust structure that can enhance the purification performance of a catalytic converter by promoting exhaust swirling and diffusion. [Solution] The exhaust passage 2 is provided with a plurality of independent passages 51 that extend individually from the exhaust port opening end 12A, a collection passage 52 into which the exhaust gases that have passed through the independent passages 51 are collected, a catalytic converter 6, and a swirling section 53 that connects the collection passage 52 and the catalytic converter 6 and swirls the exhaust gases inside. Each independent passage 51 and the collection passage 52 are shaped to curve outwards from each exhaust port opening end 12A toward the exhaust side, and the swirling section 53 is shaped to swirl the exhaust gases led out from the collection passage 51 around an axis along the cylinder arrangement direction.

Claims

1. In an engine exhaust structure comprising an engine body having a plurality of cylinders arranged in a predetermined cylinder arrangement direction and a plurality of exhaust ports extending from each of the cylinders, and an exhaust passage through which exhaust gases led out from the engine body flow, When one side is designated as the exhaust side and the other as the intake side in the engine width direction perpendicular to the cylinder arrangement direction and the vertical direction, the exhaust side of the engine body has multiple exhaust port openings, which are the outlets of the exhaust ports. The exhaust passage comprises a plurality of independent passages extending individually from each exhaust port opening towards the exhaust side in the engine width direction, a collection passage connected to the downstream end of each of the independent passages in the exhaust flow direction, to which the exhaust that has passed through the independent passages is collected internally, a catalytic converter provided downstream of the collection passage for purifying the exhaust, and a swirling section connecting the collection passage and the catalytic converter for swirling the exhaust internally. Each of the aforementioned independent passages and the aforementioned collective passages, as a whole, has a curved shape that bulges downward toward the exhaust side from each of the exhaust port opening ends. The exhaust structure for an engine is characterized in that the swirling section has a shape that causes the exhaust gas led out from the collection passage to swirl around an axis along the cylinder arrangement direction.

2. In the exhaust structure of the engine according to claim 1, An engine exhaust structure characterized in that each of the aforementioned exhaust port opening ends is formed in the central portion of the exhaust-side surface of the engine body in the direction of cylinder arrangement.

3. In the exhaust structure of the engine according to claim 1, The catalytic converter has a cylindrical shape extending in the direction of the cylinder arrangement, The exhaust structure for an engine is characterized in that the swirling portion has a shape that covers the upstream end of the catalytic converter in the exhaust flow direction from one side in the cylinder arrangement direction.

4. In the exhaust structure of the engine according to claim 1, The aforementioned rotating portion has an inner circumferential surface that is substantially circular when viewed along the cylinder arrangement direction, An engine exhaust structure characterized in that the downstream end of the manifold is connected to a lower portion of the exhaust side surface in the engine width direction of the rotating section.

5. In the exhaust structure of the engine according to claim 4, An engine exhaust structure characterized in that, in a cross-section extending vertically through the central axis of the catalytic converter, the distance between the inner circumferential surface of the swivel portion and the upstream end of the catalytic converter in the cylinder arrangement direction is smaller above the central axis of the swivel portion than below it.

6. In the exhaust structure of an engine according to any one of claims 1 to 5, The engine body has four or more of the cylinders, An engine exhaust structure characterized in that the exhaust ports of a plurality of cylinders whose combustion sequence is not consecutive are gathered inside the engine body.

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