| 摘要 |
PURPOSE:To enable a strong swirl to be ensured in an engine even when it is in low speed operation, by forming an intake port in a normally opening intake passage into a helical port shape, in the case of a device equipped with the normally opening intake passage and a low speed time closing intake passage. CONSTITUTION:An engine forms two intake ports 2, 3 in a part corresponding to each cylinder chamber 1 in a cylinder head 6 so that port outlets 11, 12 of these intake ports 2, 3 are positioned being lined in the direction parallel to a cam shaft center S in a part deflecting to the inlet side of each port from the center C of the cylinder chamber. Further the engine forms the intake port 2, positioned in the upstream side for the flow direction B of a swirl, to a pure helical port while the intake port 3, positioned in the downstream side, to a partial helical port. Each intake port 2, 3 communicates with a normally opening intake passage 70 and a low speed time closing intake passage 80, and the engine, when it is in low speed operation, inducts intake only through the normally opening intake passage 70 by closing an intake valve 40 acting as a stop valve.
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