Fluid supply apparatus

Abstract

A fluid feeding apparatus includes parallel flow passages connected at their downstream side, each parallel passage including a pressure flow controller (C) for regulating the flow of fluid and a fluid changeover valve (D) for opening and closing the passage on the downstream side of the pressure flow controller. A fluid feeding control unit (B) controls the pressure flow controllers and changeover valves so that when a changeover valve is closed a control valve (,) upstream of the changeover valve is also closed to prevent a pressure buildup at the changeover valve. In addition to the control valve (,), each pressure flow controller includes an orifice (,) downstream from the control valve, a pressure detector (,) for sensing pressure (P,) in the passage at a point between the control valve and the orifice, and a calculation control unit (,) for producing a control signal Qy for controlling the drive (,) for the control valve. The calculation control unit first calculates a flow rate signal Qc=KP,, where K is a constant and P,is the pressure sensed by the pressure detector. The calculation control unit then calculates Qy as the difference between a set point or flow rate specifying signal Qs and the calculated value Qc. Thus, the flow rate on the downstream side of the orifice is controlled by regulating the pressure P,on the upstream side of the orifice via the control valve. The fluid feeding apparatus avoids transient overshooting at the start of fluid feeding and at fluid changeover time and is suitable for use in semiconductor manufacturing facilities and other gas supply systems where high precision is required.