| 摘要 |
PROBLEM TO BE SOLVED: To provide an intake system for an internal combustion engine enabling further improvement of fuel economy of the internal combustion engine compared to conventional cases.SOLUTION: An intake system is adapted to a three cylinder internal combustion engine 1A that has an intake passage 3 including one common passage 5 and three independent passages 6 each branched from the common passage 5 for each cylinder 2a and connected to each cylinder 2a. In the intake system, an introduction passage 11 connected to an air cleaner 7 includes a change-over valve 14 enabling switching between a first position P1 that makes the introduction passage 11 long and a second position P2 that makes the introduction passage 11 short. The change-over valve 14 is switched to one of the first position P1 and the second position P2 that has higher volumetric efficiency of the internal combustion engine 1A than that of the other position when an operating point of the internal combustion engine 1A identified by the speed and torque of the internal combustion engine is within a knocking region, and is switched to the other of the first position P1 and the second position P2 when the operating point of the internal combustion engine 1A in a non-knocking region. |
