JP3552767B2 - Fluid pressure automatic control system - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a fluid automatic control system for supplying a low-viscosity liquid such as water, or a fuel gas or a gas such as air at a predetermined pressure.More specifically, the fluid pressure is controlled with high precision, The present invention relates to an automatic fluid pressure control system capable of instantaneously switching multi-stage set pressures, and further minimizing pressure fluctuations at the time of switching the set pressures, and further minimizing pressure fluctuations due to flow rate fluctuations.
[0002]
[Prior art]
2. Description of the Related Art In recent years, there has been an increasing need to use a mixed gas having a high-accuracy component structure in a wide range of technical fields such as a combustibility test of a gas combustor, a semiconductor process, a glass fiber process, and a new ceramic process including a CVD process. Particularly, in the combustibility test of a combustor, the composition standard of the fuel gas is extremely strictly specified. Therefore, in producing the mixed gas, the supply of various raw material gases must be performed with high precision under predetermined conditions, and a mixed gas having a high-precision composition is also supplied to a combustor or the like at a predetermined pressure and flow rate. Need to be done.
[0003]
In order to satisfy such demands, the present inventors have previously developed a highly accurate fluid pressure control valve (Japanese Patent Application No. 6-165350). FIG. 2 shows the structure of the fluid pressure control valve 30. According to the drawing, a primary fluid pressure flow path 32 and a secondary fluid pressure flow path 33 are formed inside a valve body 31 and a primary side of a communication flow path 34 connecting the respective flow paths 32, 33. A control space 36 is provided above the flow path on the side of the fluid pressure flow path 32 via a penetrating portion 35, and a nozzle section 44 including a valve seat 42 and a valve body 43 is formed in the middle of the communication flow path 34.
[0004]
The through portion 35 for communicating the communication flow path 34 with the control space 36 is partitioned by a balance diaphragm 50, and the inside of the control space 36 is separated from the communication flow path 34 by two control diaphragms 45 and 46. In order from the side, a pneumatic control chamber 49 to which the control air 61 is supplied, an atmospheric chamber 48 opened to the atmosphere 74, and a pressure equalizing chamber 47 communicating with the secondary fluid pressure flow path 33 are partitioned into three chambers. Have been. Further, the valve body 43 and each of the diaphragms 45, 46, 50 are connected by a valve rod 51.
[0005]
As described above, the control space 36 is partitioned into three chambers by the two connected control diaphragms 45 and 46 and the balance diaphragm 50, and the diameter difference between the control diaphragms 45 and 46 can be set arbitrarily. Since the control air pressure in 49 can be selected to an optimum value that can be supplied to the supply source with the least variation, highly accurate pressure control can be performed.
[0006]
Furthermore, when the control diaphragms 45 and 46 are integrally formed and inserted and fixed without penetrating the valve rod 51 into the connection shaft portion 52 thereof, the air chamber 48 becomes the pneumatic control chamber 49 and the pressure equalizing chamber 47. Are completely isolated from each other via the control diaphragms 45, 46, and even if one of the control diaphragms 45, 46 is broken, the control air and the controlled fluid are not mixed. In addition, reliability and stability are ensured in addition to the high accuracy described above.
[0007]
In FIG. 2, reference numeral 80 denotes a stopper mechanism which is inserted and fixed from the outside into a space communicating with the secondary-side fluid pressure flow path 33 of the through portion 35, and the stopper mechanism 80 is a closing mechanism supplied from a closing air supply source 81. A stopper cylinder 82 for operating the piston 82a so that the piston 82a can be contracted and moved by air for use. The cylinder 82 is operated to contract the piston 82a against the bias of the spring 83, and the valve seat 42 of the nozzle portion 44 is The restriction of the valve body 43 that comes into contact with is released, and the control operation of the valve body 43 is enabled.
[0008]
[Problems to be solved by the invention]
However, even if the pressure control valve is capable of controlling the predetermined secondary pressure with high accuracy as described above, simply incorporating this in the fluid pressure circuit will cause, for example, a sudden pressure fluctuation on the user side. Occurs, there is a considerable time delay before the control pressure stabilizes. The occurrence of such pressure fluctuation and time delay is a problem to be avoided as much as possible in fluid pressure control requiring high accuracy as described above.
[0009]
Further, according to the conventional general pressure control system, the pressure control valve employs a mechanical mechanism for changing the set pressure by a spring or the like. Therefore, when the set pressure is changed, the adjustment operation must be performed sequentially. A continuous adjustment in relation to the pressure rise and fall times was not possible.
[0010]
An object of the present invention is to avoid sudden pressure fluctuations that occur at the time of control pressure startup and switching of the same pressure that cannot be normally avoided as described above, and that a predetermined set pressure can be obtained repeatedly at a desired set time. Another object of the present invention is to provide a fluid pressure automatic control system capable of always controlling the fluid pressure on the secondary side with high accuracy.
[0011]
[Means for Solving the Problems]
Such an object is achieved by a fluid pressure automatic control system in which a central processing unit, a fluid pressure control circuit, and a pressure detection unit, which constitute the main components of the present invention, are incorporated. An electro-pneumatic converter for converting to a control air pressure based on a command electric signal, a pressure control valve connected to the electro-pneumatic converter for controlling the secondary pressure to a set pressure, and a primary pressure control valve A return line connecting the inlet of the side flow path and the outlet of the secondary side flow path, and a return pump interposed in the return line, wherein the return pump is activated simultaneously with the activation of the fluid pressure. The fluid pressure automatic control system is characterized in that a part of the secondary fluid pressure is continuously flown back to the primary flow path.
[0012]
According to a preferred embodiment, the central processing unit stores a plurality of pressure arrival times for a plurality of preset pressures, respectively, and combines the arrival times with a command electric signal to the electro-pneumatic converter. A predetermined set pressure is repeatedly obtained with a plurality of arrival times, and an input / output terminal is provided for enabling mutual communication with an external personal computer or a sequencer. It is preferable that the reflux pressure be 1.0 to 1.8 l / min.
[0013]
[Action]
By installing a forced return line between the primary side line and the secondary side line of the pressure control valve, the pressure control valve is provided with a predetermined pressure from the primary side hydraulic pressure passage to the secondary side hydraulic pressure passage. Since the controlled fluid having the pressure continuously flows, the peripheral members follow well even when the fluid pressure control circuit is started or when the set pressure is switched, and a stable control fluid pressure can be obtained in a short time. Can be
[0014]
This stabilization of the set pressure in a short time and its reproducibility also allow the pressure rise and fall times to be set freely. This means that, for example, in a gas combustion test, when finding out the operation timing of the safety valve based on the gas pressure drop during combustion, by setting a continuous pressure drop within a predetermined time according to the present invention in advance, the safety valve This means that the drop pressure value at the time of operation can be confirmed with high accuracy.
[0015]
【Example】
Hereinafter, the present invention will be specifically described with reference to the drawings. FIG. 1 shows an embodiment of a fluid pressure automatic control circuit based on the system of the present invention. The automatic fluid pressure control circuit in the present embodiment is unitized, and all the related members are integrated into a single housing 1. The housing 1 is provided with ports such as control air pressure, controlled fluid pressure, and sensor introduction pressure, and connection terminals of a central processing unit (microcomputer) connected to an external device such as a personal computer or a sequencer. Therefore, the central processing unit has a communication function with an external device and a remote control function.
[0016]
In the figure, reference numeral 41 denotes a pressure control valve for controlling the secondary pressure of the fluid to be controlled to a predetermined pressure, and the pressure control valve 30 has a precision pressure control shown in FIG. A valve has been applied. The housing 1 is provided with connection ports 1a and 1b to external pipes connected to the inlet of the primary fluid pressure and the outlet of the secondary fluid pressure of the pressure control valve 30, respectively. An electro-pneumatic converter 60 is connected to the pneumatic control chamber 49 of the pressure control valve 30. The electric / pneumatic converter 60 is connected to an external control air pressure supply source (not shown), and supplies a predetermined control air pressure 61 to the pneumatic control chamber 49 in a multi-stage manner. The most stable supply is performed when the control air pressure is in the range of 4 to 7 kg / cm ² .
[0017]
Further, the electric / pneumatic converter 60 is electrically connected to a D / A conversion unit of the central processing unit 20. When the electric / pneumatic converter 60 receives an electric switching signal from the central processing unit 20, the electric / pneumatic converter 60 performs a predetermined operation by the switching signal. The control pressure is directly sent to the pneumatic control chamber 49 of the pressure control valve 30. According to this embodiment, based on data preset in the central processing unit 20 (data of the pressure and stabilization time), 15 stages of reproducibility in the range of 1~400mmH ₂ O For pressure control of the gas In the case of liquid pressure control, the pressure can be switched in a range of 0.01 to 10 kg / cm ^{2 in} the same 15 steps with reproducibility.
[0018]
A pressure sensor 10 is connected to the A / D converter of the central processing unit 20, and a detection pressure input port 1 c and a detection fluid discharge port 1 d of the pressure sensor 10 are provided in the housing 1. Normally, the input port 1c of the detection pressure of the pressure sensor 10 is connected to a fluid pressure introduction path of various external devices (not shown) connected to the secondary fluid pressure flow path 33 of the pressure control valve 30, and controls the secondary fluid pressure. At the same time, the detection signal is sent to the central processing unit 20, and the central processing unit 20 performs a predetermined comparison operation. The supplied control air pressure is finely switched, and the secondary fluid pressure is feedback-controlled.
[0019]
The pressure control valve 30 is provided with a reflux pump 70 which is the most characteristic part of the present invention. That is, a reflux pipe 71 is provided between the primary pipe 41a and the secondary pipe 41b of the pressure control valve 30, and a reflux pump 70 is installed in the reflux pipe 71. The recirculation pump 70 is connected to the internal power supply 2 and is started when the power supply 2 is turned on, and is always activated during the operation of the automatic fluid pressure control circuit, and the partial flow rate of the secondary piping 41b is reduced. Is forcibly recirculated to the primary side piping passage 41a. In the present invention, the reflux pressure is set in a range of 1.0 to 1.8 l / min. The reflux pressure is 1. When the pressure is lower than 0 l / min, the influence of sudden pressure fluctuation at the time of switching the control pressure is still large. When the pressure exceeds 1.8 l / min, the influence of the recirculation pressure becomes large, and the load capacity range for the controlled fluid is reduced. Become smaller.
[0020]
By thus installing the forced recirculation line 71 between the primary side piping line 41a and the secondary side piping line 41b of the pressure control valve 30, the pressure control valve 30 is connected to the primary side fluid pressure flow path 32 from the secondary side. Since the controlled fluid having the predetermined pressure continuously flows through the fluid pressure flow path 33, the peripheral members follow well even when the set pressure is rapidly changed, and a stable control fluid pressure can be obtained in a short time. However, since the set pressure and the stabilization of the switching pressure are all controlled by the digital signal from the central processing unit 20 as described above, the response is fast and reproducible because the adjustment is not performed by the conventional adjustment screw. It will be excellent.
[0021]
FIG. 3 shows the ignition characteristics of the No. 20 water heater at the time of the combustion test. The solid line is the same characteristic diagram when the above-mentioned automatic fluid pressure control circuit of the present invention is applied, and the imaginary line is the automatic fluid pressure control circuit. FIG. 6 is a characteristic diagram when the forced recirculation circuit is omitted from FIG. As is clear from FIG. 3, when the normal fluid pressure control system is used, a large pressure drop (about 150 mmH ₂ O) occurs at the time of ignition, and it takes about 2 seconds until the combustion gas pressure is stabilized. However, when the present invention is applied, only a decrease in gas pressure of about 17 mmH ₂ O at the time of ignition occurs, and the time required for the combustion gas pressure to stabilize is extremely short at about 1.2 seconds. I understand that there is.
[0022]
4, adjustment pressure characteristics when the set pressure of the control fluid using the fluid pressure automatic control circuit of the present invention (air) is switched and rapidly in _{OmmH 2 O → 300mmH 2 O →} 20mmH 2 O and large value Is shown. As is apparent from the figure, sharply from 0 mm H ₂ O 300MmH stable pressure is obtained to ₂ O from a minimum value at about 3 to 4 seconds in order to boost up to a maximum value, also from 300MmH ₂ O to 20 mm H ₂ O It can also be seen that an extremely smooth set pressure (20 mmH ₂ O) can be obtained in a short time of 3 to 4 seconds even when the pressure is lowered.
[0023]
The 5 and 6, by using the fluid pressure automatic control circuit of the present invention, air pressure indicates a tone pressure characteristics when the sequentially switched every 50 mm H ₂ O between 50 mm H ₂ O and 300mmH ₂ O ing.
[0024]
FIG. 5 is a characteristic diagram at the time of boosting, and FIG. 6 is a characteristic diagram at the time of step-down. As is clear from these figures, it can be understood that the pressure switching is performed in a short time (1 second to 1.7 seconds) and smoothly over the entire range. This indicates that, since the digital pressure is set by the central processing unit 20 when the set pressure is switched in the present invention, reproducibility of the set value is guaranteed in addition to the forced circulation circuit. Also in this case, the operation of the forced recirculation circuit is maintained, and a gas of 1.0 to 1.8 l / min always flows through the pressure control valve 30. The fact that the gas pressure can be raised and lowered in a highly accurate and reproducible manner along the set curve in this way leads to the ability to arbitrarily set the pressure rise and fall per unit time, which is input to the central processing unit 20 in advance. If this is done, an arbitrary continuous pressure increase / decrease curve can be realized.For example, in a test of a combustor or the like, when a safety valve is operated due to a decrease in gas pressure, the gas pressure during the operation can be objectively and accurately confirmed. You will get.
[0025]
Although the above embodiment is an example in which the automatic fluid pressure control system of the present invention is unitized, the system of the present invention can also be directly incorporated into a normal fluid pressure circuit. Therefore, in the case where water is branched from the main pipe to many branch pipes and the like and water is distributed, by installing the automatic fluid pressure control system of the present invention for each branch pipe, it is possible to always keep the water pressure of the distribution destination constant. .
[0026]
【The invention's effect】
As is clear from the above description, according to the automatic fluid pressure control system of the present invention, a predetermined fluid pressure is always forcibly applied to the pressure control valve even when the operation is stopped or the control pressure is switched in the system. As a result, no rapid and large pressure fluctuations occur inside the pressure control valve when the system is started or when the pressure is switched, so that the control pressure can be stabilized quickly, especially when the mixed gas is mixed. This is extremely effective when high-precision fluid pressure control is strictly required, such as in manufacturing and inspection of combustion gas of a combustor.
[0027]
The continuous control of the fluid pressure with high precision and excellent reproducibility as described above in the present invention enables the rise and fall times of the fluid pressure to be freely set, which can be applied to various tests of the fluid pressure. This guarantees reliable and good results.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a fluid pressure automatic control circuit which is a typical embodiment of the present invention.
FIG. 2 is a sectional view showing a configuration of a precision pressure control valve applied to the automatic fluid pressure control circuit.
FIG. 3 is an ignition characteristic diagram of the automatic fluid pressure control circuit.
FIG. 4 is a pressure regulation characteristic diagram at the time of pressure switching by the automatic fluid pressure control circuit.
FIG. 5 is a pressure regulation characteristic diagram at the time of multi-stage boost switching by the fluid pressure automatic control circuit.
FIG. 6 is a pressure regulation characteristic diagram at the time of multi-stage pressure drop switching by the automatic fluid pressure control circuit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Housing 1a, 1b External piping connection port 1c Detected pressure input port 1d Detected fluid discharge port 2 Internal power supply 10 Pressure sensor 20 Central processing unit 30 Pressure control valve 31 Valve body 32 Primary fluid pressure channel 33 Secondary fluid pressure channel 34 Connection flow passage 35 Penetrating portion 36 Control space 41a Primary piping 41b Secondary piping 42 Valve seat 43 Valve 44 Nozzle 45, 46 Control diaphragm 47 Equalizing chamber 48 Atmospheric chamber 49 Pneumatic control chamber 50 Balance Diaphragm 51 Valve rod 52 Connecting shaft section 60 Electropneumatic converter 61 Control air pressure 70 Reflux pump 71 Forced return line 80 Stopper mechanism 81 Closing air supply source 82 Closing cylinder 82a Piston 83 Spring

Claims (4)

In a central processing unit, a fluid pressure control circuit, and a fluid pressure automatic control system in which a pressure detection unit is incorporated,
The fluid pressure control circuit is connected to the electric / pneumatic converter for converting into a control air pressure based on a command electric signal from the central processing unit, and the secondary pressure is set to the set pressure. A pressure control valve for controlling the pressure control valve, a return line connecting the inlet of the primary side flow path and the outlet of the secondary side flow path of the pressure control valve, and a return pump interposed in the return line. An automatic fluid pressure control system characterized in that the recirculation pump is activated simultaneously with the activation of the fluid pressure, and a part of the secondary fluid pressure is continuously forcibly recirculated to the primary channel. In the central processing unit, a plurality of arrival times are respectively set for a plurality of set pressures, and in combination with a command electric signal to the electro-pneumatic converter, a predetermined set pressure is obtained with a plurality of arrival times. 2. The automatic fluid pressure control system according to claim 1, wherein the fluid pressure automatic control system is obtained repeatedly. 2. The automatic fluid pressure control system according to claim 1, wherein the central processing unit is provided with an input / output terminal that enables mutual communication with an external device. The automatic fluid pressure control system according to claim 1, wherein the amount of reflux by the reflux pump is 1.0 to 1.8 l / min.

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