Flow control system with build-down system flow monitoring

Abstract

To provide a flow control system with build-down system flow monitoring that realizes flow monitoring close to real-time monitoring by combining build-down system flow rate measurement with the upstream side of the flow control system without using a thermal type flow sensor by effectively utilizing high pressure fluctuation resistance characteristics of the flow control system, and can be significantly downsized and reduced in cost.

Claims

1. A flow control system with build-down system flow monitoring comprising: an upstream side valve AV that opens/closes distribution of a gas from a gas supply source having a desired gas supply pressure; a flow control system with supply pressure fluctuation resistance connected to the downstream side of the upstream side valve AV; a build-down capacity BC being an internal volume of a passage communicatively connecting the outlet side of the upstream side valve AV and the inlet side of the flow control system; a temperature detection sensor T arranged to detect the temperature of a gas distributed inside the passage forming the build-down capacity BC; a pressure sensor P arranged to detect the pressure of the gas distributed inside the passage forming the build-down capacity BC; and a monitoring flow rate arithmetic and control unit CPb operably connected to control opening and closing of the upstream side valve AV, and arranged to compute and output a monitoring flow rate Q by a build-down system by dropping the gas pressure to a set lower limit pressure value by closing the upstream side valve AV after a predetermined time of t seconds after setting the gas pressure inside the build-down capacity BC to a set upper limit pressure value by opening the upstream side valve AV, wherein the monitoring flow rate Q is computed by the following equation: $Q=\frac{1000}{760}\times 60\times \frac{273}{\left(273+T\right)}\times V\times \frac{\Delta P}{\Delta t}$ wherein T is a gas temperature (° C.), Visa build-down capacity BC (1), AP is a pressure drop range (set upper limit pressure value−set lower limit pressure value) (Torr), At is a time (sec) from closing to opening of the upstream side valve AV, wherein a chamber with an internal capacity is interposed in the gas passage between the outlet side of the upstream side valve AV and the flow control system, and by changing the internal volume of the chamber, the value of the build-down capacity BC is adjusted, wherein the chamber is structured by concentrically disposing and fixing an inner cylinder and an outer cylinder, and the gap between the inner cylinder and the outer cylinder forming the chamber is used as a gas flow passage, and a pressure sensor P3 is provided in the chamber, and wherein a gas passage in which the gas is distributed upward from the lower side is provided inside the inner cylinder, and the gas is made to flow into the gap between the inner cylinder and the outer cylinder from the upper end surface of the inner cylinder.

2. The flow control system with build-down system flow monitoring according to claim 1, wherein the flow control system with supply pressure fluctuation resistance is a pressure type flow control system FCS including a control valve CV, an orifice OL or a critical nozzle, a pressure sensor Pi, and a flow rate arithmetic and control unit CPa; and wherein the build-down capacity BC is the internal volume of a passage communicatively connecting the outlet side of the upstream side valve AV and the inlet side of the control valve CV of the pressure type flow control system.

3. The flow control system with build-down system flow monitoring according to claim 1, wherein the gas passage provided inside the inner cylinder is a gap G1 formed between a longitudinal slot provided at the center portion of the inner cylinder and a columnar pin inserted inside the longitudinal slot.

4. The flow control system with build-down system flow monitoring according to claim 1, wherein the build-down capacity BC is set to 1.0 to 20 cc, the set upper limit pressure value is set to 400 to 200 kPa abs, the set lower limit pressure value is set to 350 kPa abs to 150 kPa abs, and the predetermined time t is set to be within 1 second.

5. The flow control system with build-down system flow monitoring according to claim 1, wherein the build-down capacity BC is set to 1.78 cc, the set upper limit pressure value is set to 370 kPa abs, the set lower limit pressure value is set to 350 kPa abs, the pressure drop range AP is set to 20 kPa abs, and the predetermined time t is set to be within 1 second.

6. The flow control system with build-down system flow monitoring according to claim 1, wherein the upstream side valve AV is a fluid pressure-operated solenoid direct-mounting type motor-operated valve or solenoid direct-operated type motor-operated valve, and a recovery time of the gas pressure from the set lower limit pressure value to the set upper limit pressure value by opening of the upstream side valve AV is set to be shorter than the gas pressure drop time from the set upper limit pressure value to the set lower limit pressure value by closing of the upstream side valve AV.

7. The flow control system with build-down system flow monitoring according to claim 1, wherein by inserting a bar piece to the inside of a gas flow passage between the outlet side of the upstream side valve AV and the flow control system, the passage sectional area of the gas flow passage is changed to adjust the build-down capacity BC and linearize the gas pressure drop characteristic.

8. The flow control system with build-down system flow monitoring according to claim 1, wherein a flow rate arithmetic and control unit CPa of the flow control system and the build-down monitoring flow rate arithmetic and control unit CPb are integrally formed.

9. A flow control system with build-down system flow monitoring comprising: an upstream side valve AV that opens/closes distribution of a gas from a gas supply source having a desired gas supply pressure; a flow control system with supply pressure fluctuation resistance connected to the downstream side of the upstream side valve AV; a build-down capacity BC being an internal volume of a passage communicatively connecting the outlet side of the upstream side valve AV and the inlet side of the flow control system; a temperature detection sensor T arranged to detect the temperature of a gas distributed inside the passage forming the build-down capacity BC; a pressure sensor P arranged to detect the pressure of the gas distributed inside the passage forming the build-down capacity BC; and a monitoring flow rate arithmetic and control unit CPb operably connected to control opening and closing of the upstream side valve AV, and arranged to compute and output a monitoring flow rate Q by a build-down system by dropping the gas pressure to a set lower limit pressure value by closing the upstream side valve AV after a predetermined time of t seconds after setting the gas pressure inside the build-down capacity BC to a set upper limit pressure value by opening the upstream side valve AV, wherein the monitoring flow rate Q is computed by the following equation: $Q=\frac{1000}{760}\times 60\times \frac{273}{\left(273+T\right)}\times V\times \frac{\Delta P}{\Delta t}$ wherein T is a gas temperature (° C.), Visa build-down capacity BC (1), AP is a pressure drop range (set upper limit pressure value−set lower limit pressure value) (Torr), At is a time (sec) from closing to opening of the upstream side valve AV, wherein a chamber with an internal capacity is interposed in the gas passage between the outlet side of the upstream side valve AV and the flow control system, and by changing the internal volume of the chamber, the value of the build-down capacity BC is adjusted, wherein the chamber is structured by concentrically disposing and fixing an inner cylinder and an outer cylinder, and the gap between the inner cylinder and the outer cylinder forming the chamber is used as a gas flow passage, and a pressure sensor P3 is provided in the chamber, wherein the inner cylinder is an inner cylinder with slits inside of which the gas is distributed, and wherein the inner cylinder is an inner cylinder provided with slits or a filter medium inside of which the gas is distributed, or an inner cylinder made of a filter medium or a porous ceramic material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic structural diagram of test equipment for measuring flow monitoring characteristics of a flow control system with build-down system flow monitoring according to an embodiment of the present invention.

(2) FIG. 2 is an explanatory view of a pressure drop state of build-down system flow monitoring.

(3) FIG. 3 is a diagram showing an example of a pressure recovery characteristic curve at the time of build-down system flow rate measurement.

(4) FIG. 4 is a partial enlarged view of FIG. 4.

(5) FIG. 5 is a diagram showing a pressure recovery characteristic curve in Test 1.

(6) FIG. 6 is a diagram showing a pattern of the pressure drop characteristic (controlled flow rate=100 sccm).

(7) FIG. 7 is a diagram showing a pattern of the pressure drop characteristic (controlled flow rate=50 sccm).

(8) FIG. 8 is a diagram showing a pattern of the pressure drop characteristic (controlled flow rate=10 sccm).

(9) FIG. 9 is a diagrammatic drawing showing a relationship between an elapsed time from closing of the upstream side valve AV and flow rate stability (build-down capacity BC=1.78 cc).

(10) FIG. 10 is a diagrammatic drawing showing a relationship between an elapsed time from closing of the upstream side valve AV and flow rate stability (build-down capacity BC=9.91 cc).

(11) FIG. 11 is a diagram showing flow rate accuracy at 10-times repeated measurement.

(12) FIG. 12 is a schematic front view of a flow control system with build-down system flow monitoring according to a first illustrative example of the present invention.

(13) FIG. 13 is a schematic front view of a flow control system with build-down system flow monitoring according to a second illustrative example of the present invention.

(14) FIG. 14 is a cross sectional view showing a state where a bar piece Cu is inserted into a flow passage.

(15) FIG. 15 is a pressure drop characteristic curve (N.sub.2: 10 sccm) when no bar piece Cu is inserted.

(16) FIG. 16 is a pressure drop characteristic curve (N.sub.2: 10 sccm) when a bar piece Cu with a diameter of 2 mm is inserted.

(17) FIG. 17 is a pressure drop characteristic curve (N.sub.2: 10 sccm) when a bar piece Cu with a diameter of 3 mm is inserted.

(18) FIG. 18 is a pressure drop characteristic curve (N.sub.2: 50 sccm) when no bar piece Cu is inserted.

(19) FIG. 19 is a pressure drop characteristic curve (N.sub.2: 50 sccm) when a bar piece Cu with a diameter of 2 mm is inserted.

(20) FIG. 20 is a pressure drop characteristic curve (N.sub.2: 50 sccm) when a bar piece Cu with a diameter of 3 mm is inserted.

(21) FIG. 21 is a pressure drop characteristic curve (N.sub.2: 100 sccm) when no bar piece Cu is inserted.

(22) FIG. 22 is a pressure drop characteristic curve (N.sub.2: 100 sccm) when a bar piece Cu with a diameter of 2 mm is inserted.

(23) FIG. 23 is a pressure drop characteristic curve (N.sub.2: 100 sccm) when a bar piece Cu with a diameter of 3 mm is inserted.

(24) FIG. 24 is a diagrammatic drawing showing a changed state of the flow rate stabilization time when a bar piece Cu is used (build-down capacity BC=1.78 cc).

(25) FIG. 25 is a diagrammatic drawing showing a changed state of the flow rate stabilization time when a bar piece Cu is used (build-down capacity BC=9.91 cc).

(26) FIG. 26 is a structural diagram of a flow control system with build-down system flow monitoring according to a third illustrative example of the present invention.

(27) FIG. 27 is a diagrammatic drawing showing a relationship between the gas flow rate (sccm) and the pressure drop gradient (kPa/sec) in a case where the measurement enabling time is set to 1 second or less in each of the chambers A to E used in the third illustrative example.

(28) FIG. 28 is a diagram showing a pattern of the pressure drop characteristic when the pressure drop gradient is 20 kPa/sec in each of the chambers A to E used in the third example.

(29) FIG. 29 is a diagrammatic drawing showing a relationship between an elapsed time from closing of the upstream side valve AV and the flow rate stability of each of the chambers A to E used in the third illustrative example.

(30) FIG. 30 is a diagrammatic drawing showing a relationship between flow rate accuracy (% S.P.) and the flow rate (sccm) in repeated measurements in the chamber A and the chamber B used in the third illustrative example.

(31) FIG. 31 is a diagrammatic drawing showing a relationship between flow rate accuracy (% S.P.) and the pressure drop gradient (kPa/sec) in repeated measurements in the chamber A and the chamber B used in the third example.

(32) FIG. 32 is a longitudinal sectional view showing a second instance of the chamber used in the third illustrative example.

(33) FIG. 33 is a basic structural diagram of a conventional pressure type flow control system.

(34) FIG. 34 is a basic structural diagram of a conventional flow control system with flow monitoring.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(35) Hereinafter, an illustrative embodiment of the present invention is described based on each example with reference to the drawings.

First Example

(36) FIG. 12 is a schematic front view of a flow control system with build-down system flow monitoring according to a first example of the present invention, and in FIG. 12, the reference symbol P.sub.1 denotes a pressure sensor, OL denotes an orifice, CV denotes a control valve, V.sub.1 and V.sub.2 denote inlet side valve blocks, V.sub.3, V.sub.4, and V.sub.5 denote FCS main body blocks, V.sub.6 denotes an outlet side block, V.sub.7 denotes a gas outlet joint, CP denotes an arithmetic and control unit, AV denotes an upstream side valve, L.sub.1 denotes a gas inlet side flow passage of the upstream side valve, L.sub.2 denotes a gas outlet side flow passage of the upstream side valve, L.sub.3 denotes an inlet side passage of the control valve CV, L.sub.4 denotes an outlet side passage of the control valve CV, P.sub.0 denotes a pressure sensor on the upstream side of the control valve CV, T denotes a temperature detection sensor, and F denotes a filter.

(37) The pressure type flow control system itself is known, therefore, detailed description thereof is omitted here. As a matter of course, the filter F can be omitted.

(38) The arithmetic and control unit CP is formed by integrally combining a flow rate arithmetic and control unit CPa that controls opening/closing of the control valve CV of the pressure type flow control system FCS and computes a flow rate distributed through the orifice and a monitoring flow rate arithmetic and control unit CPb that computes the build-down system monitoring flow rate and controls opening/closing of the upstream side valve AV.

(39) That is, the build-down system monitoring flow rate arithmetic and control unit CPb forming the essential portion of the present invention controls opening/closing of the upstream side valve AV, and computes and outputs a build-down system flow rate Q from the pressure sensor P.sub.0, the temperature detection sensor T, and the builddown capacity BC consisting of the inlet side passage L.sub.2 and the inlet side passage L.sub.3.

(40) As described above, in the arithmetic and control unit CP, the arithmetic and control unit CPa that performs flow rate computation and flow control of the pressure type flow control system FCS portion, and the arithmetic and control unit CPb that performs computation of the flow rate measured value Q of the build-down system flow monitoring unit, measurement of the pressure drop rate ΔP/Δt, and opening/closing control of the upstream side valve AV, etc., are integrally provided, and by inputs of a command signal and/or a setting signal into the arithmetic and control unit CP, the flow control system with build-down system flow monitoring outputs a gas fluid the flow of which is controlled to a predetermined flow rate value, and this flow rate value is monitored and displayed at least once per second.

(41) The structures and control methods of the pressure type flow control system FCS and the build-down system flow rate measuring unit are known, therefore, detailed descriptions thereof are omitted here.

(42) When a difference equal to or more than a set value occurs between the monitoring flow rate output (flow rate output from the monitoring flow rate arithmetic and control unit CPb) and the flow rate output of the pressure type flow control system FCS (flow rate output from the pressure type flow rate arithmetic and control unit CPa), a flow rate abnormality warning can be issued, or if necessary, so-called flow rate self-diagnosis of the pressure type flow control system FCS can be performed to identify the cause and the location of the flow rate abnormality.

(43) Further, when a flow rate difference equal to or more than the set value occurs, zero-point adjustment, etc., of the pressure type flow control system FCS can be automatically performed as well.

(44) In the present first example, a direct-operated type solenoid driving valve is used as the upstream side valve AV, and the build-down capacity BC is selected in the range of 1.78 to 9.91 cc. Further, the pressure drop range ΔP is selected to be 20 kPa abs (350 to 320 kPa abs), and the monitoring flow rate is output at least once or more per second.

(45) As the temperature detection sensor T, an outer surface-attaching type resistance temperature sensor is used, and it is also possible to use a thermostat type thermometer to be inserted into the body block V.sub.3.

(46) The flow passages L.sub.2′, L.sub.2, and L.sub.3 forming the build-down capacity BC are formed to have inner diameters of 1.8 mm to 4.4 mm, and by appropriately selecting their inner diameters and flow passage lengths, a desired build-down capacity BC is obtained.

(47) The build-down capacity BC may be adjusted by using a chamber with a pressure sensor as in the case of the third example described later.

Second Example

(48) FIG. 13 shows a second example of the present invention in which the flow passages L.sub.2′, L.sub.2, and L.sub.3 forming the build-down capacity BC are formed to have inner diameters of 2.5 mm, 3.3 mm, and 4.4 mm, respectively, and a short bar piece, for example, a bar piece made of stainless steel is inserted into each flow passage L.sub.2′, L.sub.2, L.sub.3 to simulatively narrow a part of the pipe inner diameter and adjust the total internal capacity BC to 1.78 to 9.91, and accordingly, the pressure drop characteristic is improved.

(49) In FIG. 13, components except for the respective flow passages L.sub.2′, L.sub.2, and L.sub.3 are the same as in FIG. 12 according to the first example described above.

(50) In this second example, a short bar piece (length: approximately 1 to 3 mm) Cu shown in FIG. 14 is inserted to an appropriate position inside each of the respective flow passages L.sub.2′, L.sub.2, and L.sub.3, specifically, a bar piece with an outer diameter of 3 mm (or a bar piece with an outer diameter of 2 mm) is provided at a part of the flow passage L.sub.3 with the inner diameter of 4.4 mm, or a bar piece Cu with an outer diameter of 2 mm is provided at the portion of the flow passage L.sub.2.

(51) FIG. 15 to FIG. 17 show changed states of the pressure drop characteristic in the case where the bar piece Cu is inserted (the flow passage inner diameter is changed) when the gas is N.sub.2, the flow rate is 10 sccm, the build-down capacity BC=1.78 cc, and the pressure drop ΔP is 20 kPa abs, and FIG. 15 shows the case where no bar piece Cu is provided (that is, under the same condition as in FIG. 8), FIG. 16 shows the case where a bar piece Cu with a diameter of 2 mm is inserted to one position, and FIG. 17 shows the case where a bar piece with a diameter of 3 mm is inserted to one position.

(52) FIG. 18 to FIG. 20 show the pressure drop characteristic under the same state as in FIG. 15 to FIG. 17 when the flow rate of the N.sub.2 gas is set to 50 sccm, and further, FIG. 21 to FIG. 23 show the pressure drop characteristic when the N.sub.2 gas flow rate is set to 100 sccm.

(53) As is clear from comparison among FIG. 15, FIG. 16 and FIG. 17, among FIG. 18, FIG. 19 and FIG. 20, and among FIG. 21, FIG. 22 and FIG. 23, in the second example, linearity of the pressure drop characteristic is significantly improved by using the bar piece Cu, and as a result, the flow rate stabilization time from closing of the upstream side valve AV shown in FIG. 9 and FIG. 10 is shortened, and the flow rate accuracy shown in FIG. 11 is also significantly improved.

(54) FIG. 24 and FIG. 25 show changes in flow rate errors relating to the flow rate stabilization time shown in FIG. 9 and FIG. 10 when the bar piece Cu is used, and in both of the cases where the build-down capacity BC is 1.79 cc and 9.91 cc, errors can be significantly reduced, that is, the flow rate stabilization time can be shortened and the flow rate detection time can be increased.

Third Example

(55) FIG. 26 is a basic constitution diagram of a flow control system with build-down system flow monitoring according to a third example of the present invention. Major differences between this third example and the flow control systems with build-down system flow monitoring according to the first and second examples described above are that a chamber CH with a pressure sensor is used for forming the build-down capacity BC, the inner diameters of the respective gas passages L.sub.2, L.sub.3, and L.sub.5 are set to small diameters of 1.8 mm, a pressure sensor P.sub.2 is separately provided on the downstream side of the orifice, and the chamber CH is provided with a pressure sensor P.sub.3, etc., and the constitutions of the other members are substantially the same as in the first and second examples.

(56) That is, in this third example, a small-sized pressure chamber CH is provided between the upstream side valve AV and the control valve CV of the pressure type flow control system FCS, and by adjusting the internal volume of the pressure chamber CH, the build-down capacity BC is adjusted.

(57) This pressure chamber CH is formed into a double cylinder consisting of an outer cylinder CHa and an inner cylinder CHb, and a gap G between the inner and outer cylinders CHa and CHb is selected to be 1.8 mm in the present embodiment.

(58) The internal volume of the pressure chamber CH is selected to be approximately 1.3 to 12 cc, and the pressure sensor P.sub.3 is attached to this pressure chamber CH.

(59) In FIG. 26, the reference symbol V.sub.6 denotes a chamber outlet side block, and P.sub.1, P.sub.2, and P.sub.3 denote pressure sensors.

(60) In this third example, the volume of the pressure chamber CH can freely be selected, and the gas flow passages L.sub.5 and L.sub.3, etc., can be formed to have the same small diameter (for example, a diameter of 1.8 mm), so that the build-down capacity BC can be accurately and easily set to a predetermined capacity value.

(61) In detail, as a chamber CH for testing, five kinds of chambers having the gaps G set to 1.8 mm and 3.6 mm and sized as shown in Table 3 were prepared, and the system shown in FIG. 26 using these chambers was applied to the test equipment shown in FIG. 1 and the relationship, etc., among the gas flow rate (sccm), the pressure drop gradient (kPa/sec), and the pressure drop time (sec), etc., was investigated.

(62) In the investigation using the test equipment shown in FIG. 1, the temperature detection sensor T was attached and fixed to the outer surface of the chamber CH. The volume of the gas flow passages L.sub.3 and L.sub.5 other than the chamber CH is 0.226 cc.

(63) TABLE-US-00003 TABLE 3 Chamber A Chamber B Chamber C Gap 1.8 mm Gap 1.8 mm Gap 2.4 mm Height 14.0 mm Height 92.0 mm Height 92.0 mm Diameter 18.0 mm Diameter 18.0 mm Diameter 18.0 mm Chamber 1.58 cc Chamber 8.72 cc Chamber 11.15 cc Other 0.226 cc Other 0.226 cc Other 0.226 cc flow flow flow passage passage passage volume volume volume Actual 2.31 cc Actual 9.70 cc Actual 11.55 cc total total total volume volume volume Chamber D Chamber E Gap 3.0 mm Gap 3.6 mm Height 92.0 mm Height 92.0 mm Diameter 18.0 mm Diameter 18.0 mm Chamber 13.35 cc Chamber 15.31 cc Other 0.226 cc Other 0.226 cc flow flow passage passage volume volume Actual 13.91 cc Actual 15.45 cc total total volume volume

(64) FIG. 27 shows the results of measurement of the relationship between the gas flow rate (sccm) and the pressure drop gradient (kPa/sec) in each case of using the chambers A to E when the pressure drop time (b) in FIG. 2 was set to be within 1 second, and although the volume of the flow passages L.sub.5 and L.sub.3 of the pressure type flow control system FCS, etc., shown in FIG. 26 was selected to be 0.226 cc as described above, each of the actual build-down capacities in FIG. 26 in the state where the system was assembled to the test equipment were 2.31 cc to 15.45 cc.

(65) As is also clear from FIG. 27, when the pressure drop range ΔP is set to 20 kPa/sec, in the case of the chamber A, the flow rate of 25.2 sccm can be measured, in the case of the chamber B, 106.6 sccm can be measured, and in the case of the chamber E, 169.0 sccm can be measured.

(66) FIG. 28 is a diagrammatic drawing similar to FIG. 6 to FIG. 8, showing linearity of the pressure drop when the gas flow rate was adjusted so that the pressure drop gradient reached 20 kPa/sec in the test equipment shown in FIG. 1. The measured data were acquired by the data logger NR shown in FIG. 1.

(67) As is clear from FIG. 28, the smaller the build-down capacity BC of the chamber CH (that is, the chamber A, B, etc.) is, the more excellent the linearity of the pressure drop characteristic.

(68) FIG. 29 shows the results of obtaining flow rate measurement errors caused by deviations from the linearity of the pressure drop characteristic curve by measuring 5 points every 0.25 seconds within the flow rate measurement enabling time (b) within 1 second as in the case of FIG. 9 and FIG. 10, and proves that the smaller the build-up capacity BC of the chamber A, B, the earlier the flow rate error decreases from the start of the pressure drop (that is, the more excellent in linearity of the pressure drop characteristic).

(69) FIG. 30 shows the results of investigation on the reproducibility of the flow rate measurement accuracy by using the chamber A and the chamber B, and the investigation was performed for the same purpose as in the case of FIG. 11.

(70) In this flow rate measurement accuracy reproducibility test, to stabilize the pressure drop gradient, the measurement was performed after a predetermined waiting time from closing of the upstream side valve AV, and the measurement was performed for a long period of time to obtain the reproducibility, however, the flow rate output time was set to be within 1 second in each case.

(71) As is also clear from FIG. 30, in view of reproducibility, the flow rate of 3 to 50 sccm is the applicable range in the case of the chamber A, and 30 to 300 sccm is the applicable range in the case of the chamber B.

(72) Table 4 shows basic data used for preparing the diagrammatic drawing showing reproducibility of the flow rate measurement accuracy shown in FIG. 30, and the chamber A (build-down capacity BC=2.31 cc) and the chamber B (build-down capacity BC=9.47 cc) are set as test objects.

(73) TABLE-US-00004 TABLE 4 Chamber A (BC = 2.31 cc) Flow rate sccm 1 2 3 5 10 20 30 50 Temperature ° C. 22.7 23.0 23.1 22.8 22.6 22.6 22.6 22.7 Gradient kPa/sec 0.8 1.6 2.4 4.0 7.9 16.1 23.4 39.2 Measurement kPa abs. 370 370 370 370 370 370 370 370 start pressure Measurement kPa abs. 368 365 365 363 355 350 350 350 end pressure Measurement kPa 2 5 5 7 15 20 20 20 pressure range: P Measurement sec 2.73 3.42 2.28 1.91 2.05 1.37 0.91 0.55 time: t Chamber B (BC = 9.47 cc) Flow rate sccm 5 10 20 30 50 100 200 300 400 Temperature ° C. 22.7 23.0 22.4 22.4 22.5 22.5 22.5 22.6 22.59 Gradient kPa/sec 0.9 1.9 3.8 5.7 9.4 18.9 37.7 57.3 77.204 Measurement kPa abs. 370 370 370 370 370 370 370 370 370 start pressure Measurement kPa abs. 368 367 365 360 350 350 350 350 350 end pressure Measurement kPa 2 3 5 10 20 20 20 20 20 pressure range: P Measurement sec 2.24 1.68 1.40 1.87 2.24 1.12 0.56 0.37 0.28 time: t * Measured by changing the time and pressure range so as not to exceed 10,000 data.

(74) FIG. 31 shows the results of investigation on the relationship between the pressure drop gradient (kPa/sec) and the error (% S.P.) of the chamber A and the chamber B from the data shown in Table 4 above, and proves that the flow rate measurement error (% S.P.) is within the range of ±1% as long as the pressure drop gradient is in the range of 2 to 60 kPa/sec.

(75) FIG. 32 shows a second instance of the chamber CH forming the build-down capacity BC used in a third example of the present invention. The chamber CH according to this second instance is formed of an outer cylinder CHa and an inner cylinder CHb, and further, at the center of the inner cylinder CHb, a longitudinal slot 1 circular in section is provided downward from the upper end, and the lower side of the longitudinal slot is connected to the gas outlet passage L.sub.2 of the upstream side valve AV through a gas passage 1a.

(76) A longitudinal and columnar pin 2 having a flange portion 2a on the upper end is inserted and fixed into the longitudinal slot 1 at the center of the inner cylinder CHb from the upper side, and the longitudinal slot is communicatively connected to the inside of the gap G forming the gas passage through a plurality of small holes 2b provided in the flange portion 2a, and the end portion of the gap G is communicatively connected to the gas outlet passage L.sub.5 of the chamber outlet side block.

(77) That is, in the pressure chamber CH of this second instance, the gas flowed from the lower side toward the upper side of the inner cylinder CHb flows into the gap G between the outer cylinder CHa and the inner cylinder CHb from the upper end of the inner cylinder CHb.

(78) The gap G between the outer cylinder CHa and the inner cylinder CHb of this chamber CH is selected to be 1 to 2 mm, the gap G.sub.1 between the longitudinal slot 1 and the columnar pin or screw body 2 is selected to be 0.4 to 0.8 mm, and the height of the inner cylinder CHb is selected to be 30 to 35 mm, and these are used mainly for the pressure chamber CH with an internal volume V=2 to 5 cc.

(79) The form of the chamber CH used in the third example of the present invention can be changed as appropriate, and can be structured so that, for example, the outer peripheral surface of the inner cylinder CHb of the chamber CH shown in FIG. 32 is threaded, and by changing the height and pitch of the thread, the volume of the portion of the gap G is adjusted, or the longitudinal slot 1 of the inner cylinder CHb of the chamber CH shown in FIG. 32 is formed into a screw hole, and by screwing a columnar pin 2 formed of a screw rod into the screw hole, the volume of the portion of the gap G.sub.1 is adjusted.

(80) Further, instead of the longitudinal slot 1 of the inner cylinder CHb and the columnar pin 2 shown in FIG. 32, a plurality of longitudinal slits with small diameters communicatively connected to the gas passage 1a may be formed at the center portion of the inner cylinder CHb, or the portion of the longitudinal slot 1 may be made of a filter medium.

(81) It is also possible that the whole or the portion to project upward of the inner cylinder CHb shown in FIG. 32 is made of a filter medium to flow the gas flowed-in from the gas outlet passage L.sub.2 of the upstream side valve AV into the gap G through the filter medium, or the whole or the portion to project upward of the inner cylinder CHb is made of a porous ceramic material to distribute the gas from the gas outlet passage L.sub.2 of the upstream side valve AV into the gap G through the porous ceramic material.

INDUSTRIAL APPLICABILITY

(82) The present invention is widely applicable not only to gas supply equipment for semiconductor manufacturing equipment but also to gas supply equipment for chemical goods production equipment as long as it is a pressure type flow control system using an orifice or a critical nozzle.

DESCRIPTION OF REFERENCE SYMBOLS

(83) FCS: pressure type flow control system AV: upstream side valve BC: build-down capacity RG: pressure regulator N.sub.2: N.sub.2 supply source T: temperature detection sensor (resistance temperature detector) P.sub.1, P.sub.2, P.sub.3: pressure sensor CV: control valve OL: orifice V.sub.1, V.sub.2: inlet side valve block V.sub.3, V.sub.4: FCS main body block V.sub.5, V.sub.6, V.sub.8: outlet side block V.sub.7: gas outlet joint V.sub.9: chamber outlet side block CP: arithmetic and control unit CPa: flow rate arithmetic and control unit CPb: monitoring flow rate arithmetic and control unit E.sub.1: power supply for pressure type flow control system E.sub.2: power supply for arithmetic and control unit E.sub.3: power supply for solenoid valve ECV: electric drive unit NR: data logger S: signal generator PC: arithmetic and display unit L.sub.1: gas inlet side passage of upstream side valve AV L.sub.2′, L.sub.2: gas outlet side passage of upstream side valve AV L.sub.3: inlet side passage of control valve CV L.sub.4: outlet side passage of control valve CV L.sub.5: gas passage of chamber outlet side block Cu: bar piece Q: build-down flow rate CH: chamber CHa: outer cylinder CHb: inner cylinder 1: longitudinal slot of inner cylinder 1a: gas passage 2: columnar pin or screw body 2a: flange portion 2b: small hole