IDLE SPEED CONTROL METHOD FOR CONTROLLING THE IDLE SPEED OF AN ENGINE WITH A CONTINUOUS VARIABLE EVENT AND LIFT SYSTEM AND A FUEL CONTROL SYSTEM USING THE METHOD

摘要

Air quantity of ISC is roughly controlled on the basis of the lift amount of an intake valve, whose air flow rate control range is wide. The adjustment of the air quantity beyond the range of the rough control is achieved by the control based on a phase of the intake valve. As a result, a required flow rate can be achieved with high accuracy. If only the intake-valve lift amount whose air flow rate control range is wide is used to achieve the required air quantity of ISC, a fuel control system requires both a high degree of accuracy of an intake-valve lift amount sensor and a high degree of accuracy of an intake-valve lift amount control mechanism itself, which leads to high system costs.;The air quantity of ISC is roughly controlled on the basis of the intake-valve lift amount whose air flow rate control range is wide (the air quantity is controlled based on an air flow rate corresponding to each integral multiple of the air flow rate control minimum resolution). The adjustment of the air quantity beyond the range of the rough control is achieved by the control based on a phase of the intake valve. The intake-valve phase-based control makes it possible to control the air quantity within a range of about 0.4 to 1.2 times the typical air quantity at this point of time. The air quantity, therefore, can be accurately controlled so that the air quantity is kept at a target air flow rate. Accordingly, the target revolution speed of ISC can be stably achieved.