| 摘要 |
A closed loop idle speed controller for a fuel injection system operates to control an air valve which controls an air passage bypassing the main air flow. The air valve is positioned by an actuator whose output position is controlled by fuel pressure operating against a spring. The fuel pressure is controlled by a pair of solenoid-operated on-off valves, one of which responds to electrical signals representing engine speeds below a speed reference to direct fuel to the actuator and the other of which responds to signals representing speeds above the reference to permit fuel to be withdrawn from the actuator and returned to its source. Each of the solenoid on-off valves is supplied from a pulse width modulator. The engine-driven distributor provides pulses responsive to engine speed which are connected to a sample and hold circuit. The sample and hold circuit provides d.c. voltage levels proportional to engine rpm, modified with changes in engine coolant temperature, to a pair of summing amplifiers which compare the modified speed voltage with an idle speed reference voltage to produce speed error signals. Underspeed signals are connected to the pulse width modulator connected to the supply solenoid on-off valve and overspeed signals to the modulator connected to the return solenoid on-off valve. Certain auxiliary circuits provide for modified operation during starting, during hot starts, during closed throttle operation, or during deceleration with a manual transmission car.
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