IDLE SPEED CONTROL APPARATUS AND METHOD FOR AN INTERNAL COMBUSTION ENGINE

摘要

An improved idle speed control apparatus for an internal combustion engine capable of effectively preventing instantaneous fluctuations in the number of revolutions per minute of the engine when the engine load is instantaneously changed during engine idling, thereby improving the driver's driving sensation. A bypass passage is connected with an intake manifold of the engine for supplying intake air to the engine while bypassing a throttle valve in the intake manifold. A bypass air controller is disposed on the bypass passage for controlling the amount of bypass air flowing therethrough. In one embodiment, the bypass air controller operates such that when the engine load is altered instantaneously during the engine idling, the amount of intake air is gradually changed from a first level suited to a first operating condition of the engine load to a second level suited to a second operating condition of the engine load. In another embodiment, the amount of intake air is first changed swiftly from the first level to a third level, and then gradually from the third level to the second level.