| 摘要 |
PURPOSE:To improve the torque characteristic of an engine over a wide operational range, by changing the length of a first intake-air pipe connected to a first intake-air port between a length equal to the length of a second intake-air pipe connected to a second intake-air port and a length longer than the latter. CONSTITUTION:In an engine in which each engine cylinder has two intake valves, a second intake valve is made inoperative by means of a hydraulic control device 9 during low speed operation while a first intake valve V1 alone carries out its opening and closing operation with the timing suiable for the low speed operation. There is provided in a first intake-air pipe a selector valve 26 for changing over the communication of the first intake-air pipe so that the latter is communicated with an opening 18 which is communicated with an air chamber 12 at a position where the first intake-air pipe has a length equal to the length of a second intake-air pipe 11 connected to the second intake valve, or with an opening 18 in a pipe 15 which is communicated directly with a hole 16 for the pipe 15 which is communicated directly with a hole 16 for the air chamber 12. The valve 26 is operated such that the opening 18 is closed upon low speed operation while the opening 20 is opened to make the length of the pipe longer, but when the engine speed becomes higher than its intermediate speed, the second intake valve is operated, and the selector valve is changed over to make the length of the first intake-air pipe equal to that of the second intake-air pipe. |
