Flow rate range variable type flow rate control apparatus

Abstract

A pressure type flow rate control apparatus is provided wherein flow rate of fluid passing through an orifice is computed as Qc=KP1 (where K is a proportionality constant) or as Qc=KP2 m (P1−P2) n (where K is a proportionality constant, m and n constants) by using orifice upstream side pressure P1 and/or orifice downstream side pressure P2. A fluid passage between the downstream side of a control valve and a fluid supply pipe of the pressure type flow rate control apparatus comprises at least 2 fluid passages in parallel, and orifices having different flow rate characteristics are provided for each of these fluid passages, wherein fluid in a small flow quantity area flows to one orifice for flow control of fluid in the small flow quantity area, while fluid in a large flow quantity area flows to the other orifice for flow control of fluid in the large flow quantity area.

1 - 5 . (canceled) 
     
     
         6 . A flow rate range variable type flow rate control apparatus comprising:
 (a) a thermal type mass flow rate control apparatus comprising
 i. a flow rate control valve connected to a first fluid passage; 
 ii. a laminar flow element device part disposed on the first fluid passage; and 
 iii. a flow rate sensor part, wherein temperature changes in proportion to a mass flow rate of fluid are detected at the flow rate sensor part, and fluid with a predetermined set flow rate is made to flow out by opening or closing the flow rate control valve based on detected temperature of fluid flowing in the first fluid passage; and 
   (b) a second fluid passage to the flow rate control valve that comprises at least two third fluid passages arranged in parallel, wherein each third fluid passage is provided with a laminar flow element and a flow rate sensor, wherein each laminar flow element has a different coarseness from the other, and fluid flowing in a small flow quantity range is made to flow to one laminar flow element that controls flow rate of fluid flowing in the small flow quantity range while fluid flowing in the large flow quantity range is made to flow to the other laminar flow element that controls flow rate control of fluid flowing in the large flow quantity range.   
     
     
         7 . A flow rate range variable type flow rate control apparatus as claimed in  claim 6 , wherein the number of third fluid passages in parallel is two, and the corresponding two laminar flow elements include a coarse laminar flow element for large flow quantity and a fine laminar flow element for small flow quantity, and a control range of fluid flow rate is switched either to the small flow quantity range or to the large flow quantity range by operating switching valves respectively provided on each third fluid passage.