Abstract: A negative pressure control valve for generating a negative pressure has an inlet port communicating with a negative pressure source, an outlet port communicating with a negative pressure load, a diaphragm chamber with one surface defined by a diaphragm, and an atmospheric pressure chamber adjacent to the diaphragm chamber through the diaphragm and communicating with atmospheric pressure. The diaphragm holds a valve holding member. A solenoid operated mechanism which moves the valve holding member to a first or second position in accordance with an exciting current is disposed in the atmospheric pressure chamber. The valve holding member has a valve mechanism which communicates the diaphragm chamber with the atmospheric pressure chamber at the first position and seals a channel between those chambers at the second position. The solenoid operated mechanism selectively communicates the diaphragm chamber with the atmospheric pressure chamber.

Abstract: A vacuum modulating chamber of a vacuum control valve is communicated with a diaphragm chamber of a EGR valve for controlling an amount of exhaust gas to be recirculated into combustion chambers of an engine, so that a modulated negative pressure is applied thereto. The chamber is provided with a diaphragm deflected responding to the negative pressure in the chamber. The vacuum control valve is further provided with a cam member and a spring which urges the diaphragm in one direction so as to change a value at which the pressure in the vacuum modulating chamber is controlled. A push rod is movably held by a cam follower and another spring is provided for urging the push rod in the above direction. The spring force of the other spring is applied to the diaphragm, when a rotational angle of the cam member exceeds a predetermined angle, so that the negative pressure is changed rapidly.

Abstract: A vacuum modulating chamber of a vacuum control valve is communicated with a diaphragm chamber of a EGR valve for controlling an amount of exhaust gas to be recirculated into combustion chambers of an engine, so that a modulated negative pressure is applied thereto. The chamber is provided with a diaphragm deflected responding to the negative pressure in the chamber. The vacuum control valve is further provided with a cam member and a spring which urges the diaphragm in one direction so as to change a value at which the pressure in the vacuum modulating chamber is controlled, wherein a diameter of the cam member is larger than that of the diaphragm.