FLOW RATE CONTROL VALVE MECHANISM

PURPOSE:To provide a flow rate control valve having equal percentage property at a low cost by constituting means for setting the corresponding relationship between a flow rate control signal corresponding to the valve opening and the rotary angle of a rotary shaft of a control motor at a suitable position on a route of flow rate control signal. CONSTITUTION:In the case both of control and feedback potentiometers 12, 15 are linear or of equal resistance distribution, the valve opening set with the potentiometer 15 and the valve opening of a butterfly valve 1 driven through a rotary shaft 4 and a drive shaft 2 are equal to each other and no equal percentage property is provided. If the resistance distribution of either of the potentiometers 12, 15 is changed, the equilibrium position on a bridge circuit can be changed nonlinearly. In this way, the corresponding relationship between the valve opening as a flow rate control signal and the rotary of the rotary shaft 4 of the control motor 3, namely the valve opening of the butterfly valve 1, can be suitably set, and the valve 1 can be operated with equal percentage property.