Abstract: Automotive engine idle speed control device meters the flow rate of air supplied to the engine bypassing an intake pipe thereof during engine idle operation to thereby control the engine idle speed. An actuating vacuum is produced in accordance with an electrical signal and acts on a diaphragm fixed to a valve movable with the diaphragm to meter the bypass air flow. To cancel any external force acting on the valve, adjusting means is provided to control the vacuum on the diaphragm independently of the electrical signal to displace the diaphragm in a direction opposite to the direction of action of the external force on the valve.

Abstract: An idle speed control device has an electromagnetic driving portion and a flow rate controlling portion disposed in a bypass passage formed in a throttle chamber such as to bypass a throttle valve. The flow rate controlling portion has a body defining a passage for the fluid to be controlled, a seal formed in an intermediate portion of the passage, a first valve driven by the plunger of the electromagnetic driving portion through a rod such as to be brought into and out of contact with the seat, a sleeve disposed in the body, and a second valve connected through a rod to the downstream side of the first valve such as to produce a vacuum force which acts in the opposite direction to the vacuum force produced on the first valve thereby to absorb any fluctuation in the intake pressure in cooperation with the first valve, the second valve being loosely received by the sleeve.