Patent ID: 7680582

Claim:
An idling rotation speed control apparatus, for an outboard engine mounted on a boat, comprising: an engine-rotation-speed detection means for detecting a rotation speed of an engine; an engine-temperature detection means for detecting a warming-up state of the engine; an idling driving state detection means for detecting an idling driving state of the engine; a load detection means for detecting an engine load that changes depending on whether a shift-lever position of the engine is the neutral, the forward, or the backward position; an intake air amount adjusting means for adjusting an amount of intake air supplied to the engine during an idling state; and a control unit (ECU) for, while the engine is in an idling state, controlling the intake air amount adjusting means so as to make the engine rotation speed converge on a target rotation speed, based on an engine state detected by the detection means, wherein the ECU includes a basic torque ratio calculation function for calculating a ratio of torque to be generated, to engine maximal torque, that is necessary for making the engine steadily operate at a target rotation speed during idling driving; a target torque ratio calculation function for correcting the basic torque ratio, in accordance with a difference between a target rotation speed and an engine rotation speed, and calculating a target torque ratio; a target air amount calculation function for calculating an air amount necessary for generating the target torque ratio; and an intake air amount adjusting function for controlling the intake air amount adjusting means, based on the calculated air amount.