Patent ID: 7264223

Claim:
A flow rate control apparatus for controlling a flow rate of a pressure fluid, the flow rate control apparatus comprising: a body in which a fluid passage for allowing said pressure fluid to flow therethrough is formed; a valve mechanism, having a main valve body and a first flexible member connected to said main valve body, said main valve body and said first flexible member being seated on and separated from a valve seat of said body under a driving action of a driving section driven by an electric signal, so as to control said flow rate of said pressure fluid flowing through said fluid passage; and an equilibrium-retaining mechanism, which is connected at a position opposed to said valve mechanism, and which has a connecting member and a second flexible member connected to said connecting member, said connecting member and said second flexible member maintaining an equilibrium state with respect to said main valve body and said first flexible member during a valve open state when said main valve body and said first flexible member are separated from said valve seat, in accordance with a fluid pressure of said pressure fluid when said flow rate of said pressure fluid flowing through said fluid passage is changed, wherein, in said valve open state, side surfaces of said first flexible member and said main valve body function jointly as a first pressure-receiving section when said main valve body and said first flexible member are separated from said valve seat, while side surfaces of said connecting member and said second flexible member function jointly as a second pressure-receiving section, and wherein, in a valve closed state, said equilibrium state is not retained and only a partial pressure receiving area of said main valve body is exposed to said fluid while a full pressure receiving area of said second pressure-receiving section is exposed to said fluid.