Closed loop idle engine speed control with a valve operating relative to neutral position

摘要

In a closed loop idle engine speed control system the actual engine speed is compared with a reference idle speed during engine warm-up periods to control the amount of an air flow introduced to the engine through an auxiliary air delivery system so that the difference between the actual and reference engine speeds is reduced. The reference setting of the idle speed is varied as a function of the engine temperature in order to vary the actual engine speed in response to an increase in the engine temperature. The auxiliary air delivery system includes a linear solenoid type electromagnetic valve which comprises a spring-biased valve member normally maintained in a neutral position with respect to the valve seat to allow introduction of a predetermined amount of auxiliary air to the engine and a pair of coils energized respectively with a current representing the difference in engine speed to move the valve member in opposite directions to increase or decrease the auxiliary air supply.