Patent ID: 6152168
Filing Date: 2000-11-28
Classification: G05D,Y10T

Abstract:
A pressure-type fluid flow rate control apparatus comprising an orifice, a control valve provided on an upstream side of the orifice, a pressure detector provided between the control valve and the orifice, and a control unit which calculates a fluid flow rate on the basis of pressure P1 detected by the pressure detector with the equation Qc=KP1 (K=constant) and outputs, in a drive for the control valve, the difference between a set flow rate signal Qs and the calculated flow rate signal Qc as a control signal Qy, wherein the pressure P1 on the upstream side of the orifice is regulated by actuating the control valve for controlling the flow rate Q of the fluid downstream of the orifice, so that the ratio P2/P1 between the pressure P1 on the upstream side of the orifice and the downstream pressure P2 is maintained at not higher than the critical pressure ratio of the controlled fluid, characterized in that a direct touch type metal diaphragm valve unit functions as the orifice and that a ring-shaped gap between a valve seat and a diaphragm serves as a variable orifice, and a pulse motor type drive for regulating said ring-shaped gap.