Intake control device and its control method

摘要

The present invention relates to an intake control device for an engine (50) comprising: a change control means (11a) for changing a length of an intake conduit (30) between a first length (L1) and a second length (L2) shorter than the first length (L1); and a determining means (11b) for determining whether or not the length of the intake conduit (30) needs to be changed by the change control means (11a), wherein the determining means (11b) is configured to determine requirement that the first length (L1) is to be changed to the second length (L2) based on the condition that an engine load is higher than a first threshold value, and is configured to determine requirement that the second length (L2) is to be changed to the first length (L1) based on the condition that the engine load is lower than a second threshold value, and wherein the second threshold value is set lower than the first threshold value.