| 摘要 |
PURPOSE:To enhance the charge effect of intake-air over a wide rotational speed range, by communicating branch intake-air passages for a common intake- air passage, with each other, and by disposing shut-off valves which open in a high speed range in which the rotational speed of an engine exceeds a set value, in the communicating sections. CONSTITUTION:An intake-manifold 12 has branch intake-air passages 12a-12d which are connected to intake-air ports 7 in engine cylinders 4a-4d, and the upstream collecting section 12e of these branch intake-air passages 12a-12d is connected to a common intake-air passage 13. In this arrangement a communicating section 20 is connected to the intermediate sections of the passages 12a-12d so that the passages 12a-12d are communicated with each other. This communicating section 20 is communicated with the passages 12a-12d through communicating holes 21 in which shut-off valves 22 are respectively disposed. Each shut-off valve 22 is controlled to be closed in a low speed range in which the rotational speed of the engine is lower than a set value, but is opened in a high speed range in which the rotational speed of the engine is higher than the set value. With this arrangement, it is possible to enhance the charge efficiency of intake-air passage. |
