JP2004138425A - Temperature measuring instrument for pressure type flow controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To actualize a pressure type flow controller for controlling the rate of an orifice passing flow with high accuracy by simultaneously measuring a fluid pressure and a fluid temperature at a same point in the fluid. <P>SOLUTION: This pressure type flow controller controls the rate of flow passing an orifice by computing Qc = K×P<SB>1</SB>with an upstream side pressure assumed as P<SB>1</SB>when the flow velocity of a fluid passing through an orifice 4 is at the velocity of sound. The controller is characterized in that an upstream side pressure sensor comprises a resistance element whose electrical resistance varies under pressure and this resistance element as the pressure sensor is simultaneously used as a temperature sensor. In this resistance element, four resistors 41a to 41d are disposed on a pressure receiving surface to form a bridge circuit using the four resistors as four sides. A constant-current power supply 43 is connected between input terminals 42a and 42b of the bridge circuit. A voltage V<SB>p</SB>between output terminals 44a and 44b is used to detect a fluid pressure P while a voltage V<SB>T</SB>between the input terminals is used to detect fluid temperature T, thus causing the resistance element to function as a pressure-temperature sensor 10. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure type flow control device mainly used in a semiconductor manufacturing facility, a chemical plant, and the like. The present invention relates to a temperature measuring device of a pressure type flow control device used as a temperature sensor for a pressure sensor.
[0002]
[Prior art]
2. Description of the Related Art In a semiconductor manufacturing facility, a chemical plant, or the like, a plurality of gases serving as raw materials are supplied at a predetermined flow rate, and a source gas is chemically reacted in a reaction furnace to generate a target gas in many cases. In such a case, if the supply flow rate of the source gas is not accurate, the chemical reaction may be excessive or insufficient, and the source gas may remain in the target gas. In particular, if the source gas is flammable, there is a risk of explosion.
[0003]
Conventionally, in order to accurately control the gas flow rate, an orifice is arranged in a pipe, and a flow rate equation with as high a theoretical flow rate as possible through the orifice has been selected. In particular, a method of controlling the flow rate by setting the flow velocity of the gas flow passing through the orifice in a sonic region in consideration of the incompressibility of the gas flow is used.
[0004]
In this flow control method, the pressure P upstream of the orifice₁And downstream pressure P₂Pressure ratio P₂/ P₁Is smaller than the critical value of about 0.5, the flow velocity of the gas passing through the orifice reaches the sonic speed.₁Is used. Here, it is known that the proportional coefficient K depends on the type of the fluid and the fluid temperature.
[0005]
In order to control the flow rate through the orifice by the theoretical flow rate formula, the pressure P upstream of the orifice₁It is necessary to accurately measure the fluid temperature T on the upstream side. Upstream pressure P₁Is received by a diaphragm and measured by a resistance element via a pressure transmission medium. On the other hand, the fluid temperature T has been measured by placing the thermistor separately in a valve device incorporating an orifice.
[0006]
[Problems to be solved by the invention]
As described above, the upstream pressure acts in direct contact with the diaphragm and is measured by the resistance element, which is a pressure sensor, via the pressure transmission medium, so that the fluid pressure can be accurately measured. On the other hand, the thermistor, which is a temperature sensor, does not come into direct contact with the fluid, and is disposed at a position near the orifice in the valve device described above. Since the fluid continuously passes through the orifice, it is considered that the temperature near the orifice has reached the thermal equilibrium state with the fluid and the temperature is equal, and the thermistor located near the orifice can accurately reproduce the fluid temperature. Because it was thought.
[0007]
However, since the valve device is generally formed of metal, the thermal conductivity is extremely high. The heat drawn from the fluid at the orifice location transfers heat rapidly to the outer surface of the valve device, and due to this temperature gradient, even at a location some distance from the orifice is not the same as the fluid temperature. Because the thermistor has finite geometric dimensions, the measured temperature may be slightly deviated from the fluid temperature even if the thermistor is located near the orifice. Therefore, when the flow rate is calculated using the thermistor temperature as the fluid temperature, Qc = KP₁Is a first cause of inducing an error in the calculated flow rate.
[0008]
Also, Qc = KP₁Pressure P used in the calculation of₁And the fluid temperature T are theoretically the pressure and temperature at the same point of the upstream fluid. This means that the flow equation Qc = KP₁Can be understood from the fact that the pressure P and the temperature T at the same point are used in the process of deriving.
[0009]
However, in the conventional pressure type flow control device, as described above, the fluid pressure is measured by the resistance element, and the fluid temperature is measured by a separately disposed thermistor. Even if the resistance element and the thermistor are miniaturized, since both are separate, measurement points of pressure and temperature are necessarily different. In a situation where the two have a finite size and the mounting positions are different, the pressure and temperature measurement positions are slightly separated from each other, which causes a second error in the flow rate equation.
[0010]
Therefore, the temperature measuring device of the pressure type flow control device according to the present invention satisfies the theoretical requirement of the flow type by directly measuring the fluid temperature at the same position as the position where the fluid pressure is measured, and passes through the orifice. An object of the present invention is to control the flow rate of a fluid to be controlled with high accuracy. In order to achieve this object, the present invention includes the following invention groups.
[0011]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided an orifice for controlling a flow rate, a control valve provided in an upstream pipe of the orifice, and an upstream pressure P provided between the orifice and the control valve.₁Pressure sensor for detecting the pressure and the upstream pressure P₁In the pressure type flow control device for controlling the orifice passing flow rate by opening and closing the control valve while calculating the orifice passing flow rate, the upstream pressure sensor is constituted by a resistance element whose electric resistance changes when receiving pressure. A temperature measuring device for a pressure type flow control device, wherein a resistance element as a pressure sensor is also used as a temperature sensor at the same time.
[0012]
According to a second aspect of the present invention, there is provided an orifice for controlling a flow rate, a control valve provided on an upstream pipe of the orifice, and an upstream pressure P provided between the orifice and the control valve.₁Pressure sensor for detecting pressure, and a downstream pressure P provided in a pipe downstream of the orifice.₂Pressure sensor for detecting the pressure and the upstream pressure P₁And downstream pressure P₂In the pressure type flow control device for controlling the orifice passing flow rate by opening and closing the control valve while calculating the orifice passing flow rate, the upstream pressure sensor or the downstream pressure sensor changes the electric resistance when receiving pressure. Wherein the resistance element as the pressure sensor is also used as a temperature sensor at the same time.
[0013]
According to a third aspect of the present invention, in the resistance element, four resistors are disposed on the pressure receiving surface, a bridge circuit having the four resistors as four sides is formed, and a constant current power supply is provided between input terminals of the bridge circuit. A temperature measuring device of a pressure type flow control device which is connected and detects a fluid pressure by a voltage change between output terminals and detects a fluid temperature by a voltage change between the input terminals.
[0014]
A fourth invention is a temperature measuring device of a pressure type flow controller using a resistance element in which a resistance is diffused and formed on a silicon substrate.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
The present inventors have conducted intensive studies to simultaneously measure the fluid pressure and fluid temperature at the same position in the fluid, and as a result, stopped placing the pressure sensor and the temperature sensor separately, and used the pressure sensor as a temperature sensor at the same time. The present invention was conceived based on the idea that the present invention could not be used.
[0016]
The present inventors have conventionally used a resistance element as a pressure sensor when controlling the flow rate of a fluid. This resistance element utilizes the property that resistance changes when pressure is applied. Generally, four resistances are formed on a silicon substrate, and a Wheatstone bridge having the four resistances as four sides is used. Is configured.
[0017]
The principle of this pressure sensor is as follows. A constant current flows through the resistor by a constant current power supply connected between the input terminals of the Wheatstone bridge. When pressure is applied, the resistance value of the resistor changes, so that the voltage between the output terminals of the bridge changes, and the fluid pressure can be measured based on the voltage between the output terminals.
[0018]
In order to simultaneously use this pressure sensor as a temperature sensor, the present inventors focused on the input terminal of the Wheatstone bridge. Since the constant current power supply is connected between the input terminals but the voltage power supply is not connected, the voltage between the input terminals naturally changes according to the resistance change.
[0019]
The present inventors have placed this resistance element in a thermostat and measured the voltage between the input terminals while changing the temperature. As a result, they have found that the voltage changes over a wide range with respect to the temperature change. When only the pressure was changed while maintaining the temperature constant, the voltage between the input terminals hardly changed, or only the change within the error range allowed by the device of the present invention was shown.
[0020]
From the above results, it has been proved that the fluid temperature can be measured by the voltage between the input terminals of the resistance element. Therefore, hereinafter, the voltage between the input terminals is also referred to as a bridge voltage, and is used exclusively for measuring the fluid temperature. Further, since the voltage between the output terminals is used for measuring the fluid pressure as in the past, this resistance element is a pressure sensor and a temperature sensor that function for the same point of the fluid. You can also.
[0021]
Hereinafter, an embodiment of a temperature measuring device of a pressure type flow control device according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram of a flow rate control by a pressure type flow rate control device using a critical expansion condition according to the present invention. The pressure type flow controller 2 is based on the premise that the supplied fluid is under a critical expansion condition, that is, the speed of the fluid flowing out of the orifice 4 is a sonic speed.₁Is represented by
[0022]
The pressure type flow control device 2 includes an orifice 4 having an orifice hole 4a, an upstream pipe 6, a downstream pipe 8, an upstream pressure / temperature sensor 10, a control circuit 16, a valve driver 20, and a control valve 22. Are located.
[0023]
The pressure temperature sensor 10 is constituted by a resistance element, detects the fluid pressure on the upstream side by the voltage between the output terminals of the Wheatstone bridge, and detects the same point in the fluid by the voltage between the input terminals (also referred to as bridge voltage) as described later. It is configured to detect the fluid temperature of the fluid.
[0024]
The control circuit 16 is mainly composed of an electronic circuit, a microcomputer, and a built-in program. However, the control circuit 16 may be composed of only an electronic circuit, or may be composed of an electronic circuit and a personal computer. The control circuit 16 includes an electronic circuit system such as an amplifier circuit and an A / D converter (not shown), a flow rate calculating means 17 for calculating a flow rate Qc based on an experimental flow rate formula, and a flow rate setting means 18 for commanding a set flow rate Qs to be flowed. And comparison means 19 for calculating a flow rate difference ΔQ (= Qs−Qc) between the calculated flow rate Qc and the set flow rate Qs. The flow difference ΔQ may be calculated by Qc−Qs.
[0025]
On the upstream side of the pressure type flow controller 2, a gas tank 24 containing a high-pressure gas, a regulator 26 for appropriately adjusting the gas pressure of the high-pressure gas, and this gas are supplied from a supply pipe 27 to the control valve 22. Is connected.
[0026]
Further, on the downstream side of the pressure type flow control device 2, a control side pipe 29 for flowing a gas whose flow rate is controlled, a valve 30 for supplying this gas to a chamber 32, and a vacuum pump 34 are connected. The chamber 32 is a reaction chamber for generating a target gas from the supplied source gas.₂And O₂From raw material gas of H₂This is a reaction chamber for generating O moisture gas.
[0027]
Next, the control operation of the pressure type flow control device 2 will be described. On the upstream side, a gas at a predetermined pressure is supplied to the supply side pipe 27, and the supply flow rate to the upstream side pipe 6 is controlled by a control valve 22 which is opened and closed by a valve drive unit 20. At the same time, on the downstream side, the downstream pipe 8 is set at a low pressure by the vacuum pump 34.
[0028]
Evacuation by the vacuum pump 34 causes a downstream pressure P in the downstream pipe 8₂Is the upstream pressure P₁Much smaller than at least P₂/ P₁Since the critical expansion condition of about 0.5 is automatically set so as to always be satisfied, the velocity of the gas flowing out of the orifice hole 4a is the speed of sound. Therefore, the flow rate through the orifice 4 is Qc = KP₁Is represented by
[0029]
Upstream pressure P₁Is measured by the pressure temperature sensor 10. In order to perform accurate pressure measurement, the gas pressure is directly received by a diaphragm having excellent corrosion resistance, and the pressure is measured at a sensor portion of the pressure temperature sensor 10 via a pressure transmission medium. In addition, the sensor portion is designed to be extremely small so as not to disturb the gas flow. Therefore, the sensor portion is equal to the gas temperature T.
[0030]
FIG. 2 is a cross-sectional perspective view of a main part of the pressure temperature sensor 10 including a resistance element. A glass pedestal 37 is arranged on a header 35 having lead pins 36, 36, and a silicon substrate 38 supported at both ends by legs 38 a, 38 a is fixed on the glass pedestal 37. A gap-shaped space 39 is formed on the lower surface of the silicon substrate 38, and a through-hole 41 is formed continuously with the space 39.
[0031]
On the upper surface of the silicon substrate 38, four resistors 41a, 41b, 41c, 41d are formed by a thermal diffusion method. This resistor has a property that when a stress is applied to the surface, the electrical resistance changes in accordance with the stress. Therefore, when a constant current is applied, the voltage changes in accordance with the stress, and this voltage change enables pressure measurement.
[0032]
The gas pressure (fluid pressure) is received by a diaphragm (not shown) to generate a pressure P in the pressure transmission medium (fluid). The pressure P generated in the pressure transmission medium presses the upper surface of the silicon substrate 38, and the pressure P becomes a resistance. Acts on 41a-41d. On the other hand, when the space 39 is evacuated, the silicon substrate 38 is deformed only by the fluid pressure P, so that the absolute pressure of the fluid acts on the silicon substrate 38 and functions as an absolute pressure sensor. When the through-hole 41 is open to the atmosphere, the pressure difference between the fluid pressure P and the atmospheric pressure deforms the silicon substrate 38, so that the gauge pressure of the fluid acts on the silicon substrate 38 and functions as a gauge pressure sensor. .
[0033]
FIG. 3 is an equivalent circuit diagram of the resistance element shown in FIG. The resistances 41a, 41b, 41c, and 41d form four sides of a Wheatstone bridge. Input terminals 42a and 42b are connected to one diagonal point C and D, and a constant current power supply 43 is connected between the input terminals. I have. Output terminals 44a and 44b are connected to the other diagonal points AB.
[0034]
The resistances of the four resistors 41a, 41b, 41c, 41d change under the pressure P. A constant current I flows from the constant current power supply 43 in the direction of the arrow, and the potential change between AB changes due to the resistance change, and a voltage V corresponding to the fluid pressure is applied between the output terminals 44a and 44b._POccurs. In this specification, the voltage V_PIs referred to as a voltage between output terminals, and is also referred to as a pressure voltage in the sense of a fluid pressure detection voltage.
[0035]
In order to use this resistance element also for fluid temperature measurement, the present inventors paid attention to the other diagonal points C and D. The constant current I also causes a potential difference between the points CD. This potential difference can be detected between the input terminals 42a and 42b, and is therefore also referred to as a voltage between input terminals or a bridge voltage. The present inventors have determined that this bridge voltage V_TIs expected to vary significantly with fluid temperature.
[0036]
FIG. 4 is a diagram of an experimental device for measuring the pressure characteristics and the temperature characteristics of the pressure-temperature sensor 10. A pressure-type flow controller 2 equipped with a pressure-temperature sensor 10 composed of a resistance element is disposed inside a constant temperature bath CT, and a reference pressure generator PG and a vacuum pump DP are connected to a valve V.₁, V₂Is connected to the piping system PS.
[0037]
First, valve V₁And close valve V₂Is released, and the piping system PS is set in a vacuum state by the vacuum pump DP, that is, the internal pressure is set to 0 (kPa · abs). In this state, the pressure temperature sensor 10 is operated for each temperature while changing the internal temperature of the constant temperature bath CT from 25 ° C. to 100 ° C. No. 1, No. 2 and No. For three types of pressure-temperature sensors, the bridge voltage V for each temperature at zero absolute pressure_TWas measured.
[0038]
FIG. 5 is a bridge voltage-temperature characteristic diagram of three types of pressure temperature sensors. This characteristic diagram is obtained in a vacuum state where the absolute pressure is zero, the horizontal axis is the temperature T (° C.), and the vertical axis is the bridge voltage V._T(V) is shown.
[0039]
The three types of pressure temperature sensors 10 are No. 1, No. 2 and No. 3, the temperature of the thermostat CT was changed from 25 ° C. to 100 ° C. Bridge voltage V against temperature T (° C)_T(V) depends on No. 1 is a solid line; 2 is a chain line and No. 2 3 is indicated by a broken line and is almost straight.
[0040]
No. 1, No. 2 and No. 3, the bridge voltage V at 25 ° C._TAre 7.295 V, 7.380 V and 7.271 V, and the bridge voltage V at 100 ° C._TWere 8.966 V, 9.076 V, and 8.925 V. The difference in individuality between the pressure and temperature sensors is about 0.15 V at the same temperature, but the linearity of each sensor is extremely high.
[0041]
With a temperature difference of 75 ° C from 25 ° C to 100 ° C, the bridge voltage V_TAre 2.228 V (No. 1), 2.205 V (No. 2), and 2.261 V (No. 3). Therefore, the bridge voltage V per 1 ° C._TIt can be seen that the change amounts of are as large as 22.28 mV (No. 1), 22.05 mV (No. 2) and 22.61 mV (No. 3). Bridge voltage V at 1 ° C change_TChanges about 20 mV, the bridge voltage V_TIndicates that the temperature T can be measured.
[0042]
FIG. 6 is a bridge voltage-pressure characteristic diagram at the same temperature of three types of pressure temperature sensors. Bridge voltage V of pressure temperature sensor 10_TWas measured to determine how it changed with pressure. If the bridge voltage is almost independent of pressure, the bridge voltage V_TCan be used for temperature measurement.
[0043]
FIG. 6 shows two types of experimental results when the temperature is maintained at 25 ° C. and when the temperature is maintained at 100 ° C. In both cases, when the pressure P is changed from 0 to 700 (kPa · abs), the bridge voltage V_TWas measured.
[0044]
When the pressure P is changed from 0 to 700 (kPa · abs) at 25 ° C., the bridge voltage V_TChanged from 7.295 V to 7.285 V (No. 1), 7.271 V to 7.261 V (No. 2), and 7.380 V to 7.370 V (No. 3). Therefore, for a pressure change of 700 (kPa · abs), the bridge voltage V is applied to all three types of pressure / temperature sensors._TShowed only a very small change of -10 mV.
[0045]
When the pressure P is changed from 0 to 700 (kPa · abs) at 100 ° C., the bridge voltage V_TChanged from 8.966V → 8.956V (No. 1), 8.925V → 8.915V (No. 2) and 9.076V → 9.067V (No. 3). Therefore, for a pressure change of 700 (kPa · abs), the bridge voltage V of the three types of pressure temperature sensors is changed._TAre -10 mV, -10 mV, and -9 mV, and although there is a difference in the individuality of the sensor, only a very small change is shown as described above.
[0046]
In summary, for a pressure change of 700 (kPa · abs), a bridge voltage V of −10 mV at 25 ° C. and about −10 mV at 100 ° C._TChanges can be seen. Bridge voltage V_TChanges about 2 V with respect to a temperature change of 75 ° C., so 10 mV is only 0.5% of that.
[0047]
We discuss the error a bit more. Assuming that the actual working pressure of the gas fluid is 350 (kPa · abs), the bridge voltage V_TIs 10 mV / 2 = 5 mV. No. Since the pressure / temperature sensor 1 changes as much as 22.28 mV per 1 ° C., the above 5 mV gives only a temperature error of 0.224 ° C. from 5 / 22.8.
[0048]
This temperature error of 0.224 ° C. gives only an error of 0.04% in the required calculation in the gas temperature correction. If the zero point temperature drift as a pressure sensor is 0.1% per 1 ° C., an error of 0.1% × 0.224 = about 0.02% is induced for a temperature error of 0.224 ° C. Therefore, the temperature error of 0.224 ° C. only induces an error of 0.04% + 0.02% = 0.06% to 0.06%. Since the error of this pressure type flow controller is designed to be, for example, 1% or less, the error of 0.06% is only buried in the entire error.
[0049]
Therefore, a pressure-temperature sensor using a resistance element can simultaneously measure pressure and temperature without correlation, and can function as a pressure sensor and a temperature sensor at the same time. Therefore, as described above, the voltage (pressure voltage) V between the output terminals of the resistance element_PAnd measure the voltage between the input terminals, that is, the bridge voltage V_TSince the temperature measurement can be performed by using a temperature (also referred to as a temperature voltage), it can be said that the resistance element is an element suitable for being called a pressure temperature sensor.
[0050]
FIG. 7 is a detailed block diagram of the control system of the pressure type flow control device of the present invention. The above-mentioned pressure temperature sensor 10 detects the upstream pressure P of the fluid.₁And the fluid temperature T at the same point. The pressure P of this pressure temperature sensor 10₁Pressure voltage (voltage between output terminals) V_PIs amplified by the fixed amplifier circuit 45 and the variable amplifier circuit 47, and is input to the CPU 51 via the A / D converter 48, and the pressure P₁Is converted to Further, the upstream pressure P₁Is displayed outside.
[0051]
The pressure-temperature sensor 10 is composed of a resistance element.₀May be output.₀Is called a zero point drift voltage. In this case, the voltage −V is supplied via the offset D / A converter 49.₀Is output to the offset terminal 45a to forcibly set the zero point drift to zero.
[0052]
On the other hand, the pressure temperature sensor 10 detects a bridge voltage V corresponding to the fluid temperature T._TAnd outputs the bridge voltage V_TIs output to the CPU 51 via the fixed amplifier 56 and the A / D converter 58. This bridge voltage V_TIs converted into the fluid temperature T by the temperature conversion means 50.
[0053]
The fluid temperature T is input to the temperature drift correction means 60 and the gas temperature correction means 68. In the temperature drift correction means 60, the correction corresponding to the fluid temperature T is performed by the zero point correction means 62 and the span correction means 66 while utilizing the data in the memory means 64. Further, the gas temperature correction means 68 corrects the proportionality coefficient K of the calculated flow rate Qc using the fluid temperature T.
[0054]
In this way, the correct upstream pressure P₁And the proportionality constant K are calculated. From these data, the calculated flow rate Qc is calculated as Qc = KP₁Is calculated as The calculated flow rate Qc is output via the D / A converter 72 and the fixed amplifier circuit 74 and displayed on an external display device (not shown).
[0055]
The set flow rate Qs input as the target flow rate from the flow rate setting means 18 is input to the comparison means 19 via the fixed amplifier circuit 76 and the A / D converter 78. On the other hand, the calculated flow rate Qc is input from the gas temperature correction means 68 to the comparison means 19, the flow rate difference ΔQ is calculated as ΔQ = Qc-Qs, and output to the valve drive unit 20.
[0056]
The valve drive unit 20 adjusts the opening degree of the control valve 22 so that the flow rate difference ΔQ becomes zero.₁Is controlled. As a result, ΔQ becomes zero, and the calculated flow rate Qc is automatically controlled so as to match the set flow rate Qs.
[0057]
In the present invention, the surprising discovery that a resistance element conventionally used as a pressure sensor also functions as a temperature sensor has opened the way to utilize one resistance element as a pressure / temperature sensor. Therefore, as can be seen from the block diagram, it is possible to measure the pressure and the temperature with a single pressure / temperature sensor, and it has succeeded in simultaneously simplifying the circuit configuration and reducing the cost.
[0058]
FIG. 8 is a configuration diagram of a pressure-type flow control device using a non-critical expansion condition according to the present invention. The pressure type flow controller 2 is based on the premise that the supplied fluid is in a non-critical expansion condition, that is, the fluid velocity of the fluid flowing out of the orifice 4 is lower than the sonic velocity.
[0059]
When the fluid is under non-critical expansion conditions, one of the theoretical flow equations for the flow rate through the orifice is derived from Bernoulli's theorem that holds for an incompressible fluid, and Q = KP₂ ^1/2(P₁-P₂)^1/2Given by However, it is assumed that the fluid temperature does not change before and after passing through the orifice. In FIG. 8, the gas flow rate is controlled using this theoretical flow rate expression.
[0060]
In this flow rate type, the orifice passing amount Q is equal to the upstream pressure P₁And downstream pressure P₂Is calculated using both. However, since the fluid temperature T may be either the upstream side or the downstream side, the pressure temperature sensor 10 of the present invention is disposed on the upstream side, and only the pressure sensor 12 is disposed on the downstream side. Therefore, the upstream temperature P₁And the fluid temperature T are measured, and the downstream pressure P₂Is always measured, and the calculated flow rate Qc is calculated as Qc = KP₂ ^1/2(P₁-P₂)^1/2Is calculated.
[0061]
The difference from FIG. 1 is that the downstream pressure P₂Is added by an electronic circuit system and a software system for measuring the pressure by the pressure sensor 12 and inputting it to the control circuit 16. Since the operation and effect are almost the same as those in FIG. 1, the details are omitted.
[0062]
FIG. 9 is a configuration diagram of flow control by an improved pressure type flow control device utilizing non-critical expansion conditions according to the present invention. The pressure type flow control device 2 is based on the premise that the supplied fluid is under non-critical expansion conditions, but uses an improved theoretical flow type.
[0063]
Since an actual gas fluid has expandability and compressibility, Bernoulli's theorem on the premise of incompressibility only approximately holds. Therefore, Qc = KP₂ ^1/2(P₁-P₂)^1/2Is only an approximate expression. The present inventors have studied a flow rate equation which can reproduce the actual flow rate with high accuracy by improving this approximation equation.
[0064]
As this improved flow rate formula, Qc = KP₂ ^m(P₁-P₂)ⁿDecided to use. Conventionally, two parameters m and n are used as indices, and m and n are derived by fitting the actual flow rate with this flow rate equation. By using these parameters m and n, the actual flow rate could be reproduced with high accuracy.
[0065]
In this embodiment, the flow rate calculating means 17 is configured using an improved flow rate equation. Except for this point, the flow rate calculating means 17 is exactly the same as the embodiment shown in FIG. That is, the pressure temperature sensor 10 according to the present invention is disposed on the upstream side, and the pressure sensor 12 is disposed on the downstream side. The other configuration and operation and effect are the same as those in FIG. 1, and the description thereof is omitted.
[0066]
The present invention is not limited to the above-described embodiment, and it goes without saying that various modifications and design changes without departing from the technical idea of the present invention are included in the technical scope.
[0067]
【The invention's effect】
According to the first aspect, based on the inventors' novel discovery that the resistance element can simultaneously measure fluid pressure and fluid temperature, the resistance element can be used alone as a pressure sensor and a temperature sensor. Accordingly, if this resistance element is used as a pressure temperature sensor on the upstream side under a critical expansion condition in which the velocity of the fluid passing through the orifice becomes a sonic state, the temperature sensor conventionally required becomes unnecessary, and furthermore, the same as the fluid. Since one point of pressure and temperature can be measured at the same time, simplification of the circuit configuration and high performance of flow control can be realized, which can contribute to a reduction in the cost of the entire apparatus.
[0068]
According to the second invention, at least one of the upstream pressure sensor and the downstream pressure sensor is constituted by a resistance element under a non-critical expansion condition in which the orifice passage flow velocity is lower than the sound velocity, so that the resistance pressure and the fluid pressure are controlled by the resistance element. Both the fluid temperature and the fluid temperature can be measured at the same time, eliminating the need for a conventional temperature sensor, and simultaneously measuring the pressure and temperature at the same point of the fluid. Therefore, the simplification of the circuit configuration and the high performance of the flow control can be satisfied at the same time, and it is possible to contribute to the cost reduction of the whole apparatus.
[0069]
According to the third aspect of the present invention, since four resistors are arranged on the pressure receiving surface and the resistance element is constituted by the bridge circuit having the four resistors as four sides, a constant current power supply is provided between the input terminals of the bridge circuit. When connected, the fluid pressure can be detected by the voltage between the output terminals, and the fluid temperature can be detected by the voltage between the input terminals (bridge voltage). Therefore, by using a resistance element conventionally used as a pressure sensor as a pressure temperature sensor in a pressure type flow control circuit, it is possible to contribute to a reduction in the number of parts and a reduction in cost.
[0070]
According to the fourth aspect of the invention, the existing diffusion type semiconductor pressure transducer can also function as a temperature transducer. By incorporating this novel diffusion type semiconductor pressure temperature transducer into a pressure type flow rate control device, the number of parts can be reduced. By simultaneously measuring the pressure and temperature at the same point, it is possible to contribute to the enhancement of the performance of the pressure type flow control device.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of flow rate control by a pressure type flow rate control device using a critical condition according to the present invention.
FIG. 2 is a cross-sectional perspective view of a main part of a pressure temperature sensor 10 including a resistance element.
FIG. 3 is an equivalent circuit diagram of the resistance element shown in FIG.
FIG. 4 is an experimental apparatus diagram for measuring pressure characteristics and temperature characteristics of the pressure-temperature sensor 10.
FIG. 5 is a diagram showing bridge voltage-temperature characteristics of three types of pressure-temperature sensors.
FIG. 6 is a diagram showing bridge voltage-pressure characteristics of three types of pressure temperature sensors at the same temperature.
FIG. 7 is a detailed block configuration diagram of a control system of the pressure type flow control device of the present invention.
FIG. 8 is a configuration diagram of flow rate control of the pressure type flow rate control device using the non-critical expansion condition according to the present invention.
FIG. 9 is a configuration diagram of flow rate control by the improved pressure type flow rate control device utilizing non-critical expansion conditions according to the present invention.
[Explanation of symbols]
2 is a pressure type flow controller, 4 is an orifice, 4a is an orifice hole, 6 is an upstream pipe, 8 is a downstream pipe, 10 is an upstream pressure temperature sensor, 12 is a downstream pressure sensor, and 16 is a control circuit. , 17 is a flow rate calculating means, 18 is a flow rate setting means, 19 is a comparing means, 20 is a valve driving unit, 22 is a control valve, 24 is a gas tank, 26 is a regulator, 27 is a supply side pipe, 28 is a valve, and 29 is control. Side piping, 30 is a valve, 32 is a chamber, 34 is a vacuum pump, 35 is a header, 36 is a lead pin, 37 is a glass pedestal, 38 is a silicon substrate, 38a is a leg, 39 is a space, 41a to 41d are resistors, 42a and 42b are input terminals, 43 is a constant current power supply, 44a and 44b are output terminals, 45 is a fixed amplifier circuit, 45a is an offset terminal, 46 is a variable amplifier circuit, 47 is Variable amplifier circuit, 48 is an A / D converter, 49 is an offset D / A converter, 50 is a temperature conversion means, 51 is a CPU, 56 is a fixed amplifier circuit, 58 is an A / D converter, and 60 is a temperature drift. Correction means, 62 is a zero point correction means, 64 is a memory means, 66 is a span correction means, 68 is a gas temperature correction means, 72 is a D / A converter, 74 is a fixed amplifier circuit, 76 is a fixed amplifier circuit, and 78 is a fixed amplifier circuit. A / D converter, CT: constant temperature bath, P₁Is the upstream pressure, P₂Is the downstream pressure, PG is the reference pressure generator, Qc is the calculated flow, Qs is the set flow, ΔQ is the flow difference, V₀Is the zero point output drift voltage, V₁・ V₂Is a valve, V_PIs the pressure voltage, V_TIs the bridge voltage (temperature voltage).

Claims (4)

Orifice and the orifice for flow rate control, a control valve provided on the upstream side piping of the orifice, an upstream pressure sensor for detecting the upstream pressure P ₁ is provided between the orifice and the control valve, the upstream pressure P ₁ In the pressure type flow rate control device for controlling the flow rate of the orifice by opening and closing the control valve while calculating the flow rate, the upstream pressure sensor is constituted by a resistance element whose electric resistance changes when receiving pressure. A temperature measuring device for a pressure-type flow control device, wherein a resistance element as a member is used as a temperature sensor at the same time. An orifice for flow rate control, a control valve provided on the upstream side piping of the orifice, an upstream pressure sensor for detecting the upstream pressure P ₁ is provided between the orifice and the control valve, provided on the downstream side pipe of the orifice the pressure type flow rate control device for controlling the orifice passing flow rate and the downstream pressure sensor, the opening and closing of the control valve while calculating an orifice passing flow by the upstream pressure P ₁ and downstream pressure P ₂ for detecting a downstream pressure P ₂ Te Wherein the upstream pressure sensor or the downstream pressure sensor comprises a resistance element whose electric resistance changes when it receives pressure, and the resistance element as the pressure sensor is also used as a temperature sensor at the same time. Temperature measuring device for a flow control device. In the resistive element, four resistors are arranged on the pressure receiving surface, a bridge circuit having the four resistors as four sides is formed, a constant current power supply is connected between input terminals of the bridge circuit, and a The temperature measuring device for a pressure type flow control device according to claim 1, wherein a fluid pressure is detected by a voltage change of the pressure type, and a fluid temperature is detected by a voltage change between the input terminals. 4. The temperature measuring device for a pressure type flow control device according to claim 3, wherein a resistance element in which a resistance is diffused and formed on a silicon substrate is used.

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