JP3758717B2 - Gas mixing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas mixing device that mixes different types of gases.
[0002]
[Prior art]
A conventional gas mixing apparatus for mixing different types of gases will be described with reference to the drawings.
[0003]
FIG. 2 is a block diagram showing a first configuration example of a conventional gas mixing apparatus. In the figure, 50A and 50B are gas lines to which gas A and gas B are supplied, respectively. 51A and 51B are pressure adjusting valves provided in the gas lines 50A and 50B, respectively, and open and close the gas lines 50A and 50B. 52A and 52B are manual valves that manually open and close the gas lines 50A and 50B and conduct or block the flow of the gas A and gas B.
[0004]
A mass flow controller 53 controls the flow rate of the gas A. Here, the mass flow controller has a sensor that receives a voltage signal in the flow rate control portion and a valve unit that is controlled in accordance with the voltage signal received by the sensor, and converts the set flow rate to an analog voltage signal to the sensor. The flow rate of gas is controlled by giving. A mass flow meter 54 detects the flow rate of the gas B, and transmits the detection result to the control device 56 in the form of an electric signal via the electric system line 55.
[0005]
The control device 56 determines the flow rate of the gas A according to the received detection result so that the concentration of the gas A becomes a set desired concentration, and transmits an electric signal indicating the flow rate to the mass flow controller 53. In addition, an electric signal that instructs the flow rate of the mixed gas is transmitted to the mass flow controller 58 that controls the flow rate of the mixed gas flowing out through the buffer tank 57. In addition, the continuous line which connects each block in a figure shows a gas line.
[0006]
In such a configuration, a mixed gas of gas A and gas B is generated. At this time, if the flow rate of the mixed gas instructed from the control device 56 to the mass flow controller 58 changes, the gas flow rates in the mass flow controller 53 and the mass flow meter 54 change. Then, the control device 56 controls the mass flow controller 53 according to the flow rate of the gas B detected by the mass flow meter 54 so that the concentration of the mixed gas A is always constant.
[0007]
FIG. 3 is a block diagram showing a second configuration example of a conventional gas mixing apparatus. In the figure, 59 is a pneumatic valve that is opened and closed by a controller 61 via an instrument gas line 60 that transmits instrument gas in the form of an air signal. By opening / closing the pneumatic valve 59, the inflow / outflow of gas in the mass flow controllers 62A and 62B is controlled.
[0008]
63 is a pressure indicator for detecting the pressure in the buffer tank 57, and the detected value is transmitted to the controller 61 in the form of an electrical signal. A mass flow controller 64 controls the flow rate of the mixed gas in accordance with a predetermined usage flow rate. In addition, about the component similar to the component in the said FIG. 2, it shall represent using the same code | symbol and the description is abbreviate | omitted.
[0009]
In such a configuration, the control device 61 independently controls the flow rate of the gas controlled by the mass flow controllers 62A and 62B to generate a mixed gas having a desired concentration. In this case, the gas flow rate is set in a high flow rate range where the flow control accuracy of the mass flow controller is relatively good.
[0010]
The mixed gas thus generated flows out through the buffer tank 57 and the mass flow controller 64. The flow rate of the mixed gas flowing out is controlled to a predetermined use flow rate by the mass flow controller 64. Further, when the use flow rate changes, the pressure in the buffer tank 57 changes. When the pressure reaches a certain upper limit value, the pneumatic valve 59 is closed, and when the pressure reaches a certain lower limit value, the pneumatic valve 59 is opened repeatedly to maintain the supply of a predetermined flow rate. .
[0011]
[Problems to be solved by the invention]
By the way, in the gas mixing device according to the first configuration example described above, since the accuracy of gas mixing depends on the accuracy of the mass flow controller 53 and the mass flow meter 54, it is difficult to generate a mixed gas with a desired mixing accuracy. There was a problem that there was. Furthermore, the accuracy of the mass flow controller 53 and the mass flow meter 54 is different from each other, making it more difficult to satisfy the desired mixing accuracy.
[0012]
In the gas mixing device according to the second configuration example described above, the mixing accuracy depends on the accuracy of the mass flow controllers 62A and 62B and the gas in the mass flow controllers 62A and 62B is the same as the gas mixing device according to the first configuration example. Since the inflow / outflow of the gas is controlled by opening / closing the pneumatic valve 59, the flow rate of the gas changes abruptly, causing a problem of disturbing accuracy.
[0013]
The present invention has been made in view of such a problem, can reduce the mixing accuracy reduction due to the dependence on the accuracy of the equipment, can avoid concentration fluctuations due to a sudden change in the gas flow rate, and Another object of the present invention is to provide a gas mixing apparatus that enables generation of a mixed gas sufficiently satisfying a desired mixing accuracy.
[0014]
[Means for Solving the Problems]
The invention described in claim 1 is a gas mixing device for mixing different types of gases, and pressure adjusting means for letting out the pressure of various gases to be supplied at a set pressure, and the various gases flowing out from the pressure adjusting means. First flow rate control means for controlling the flow rate to flow out by a digital signal, and storage means for temporarily storing and supplying a mixed gas obtained by mixing the various gases flowing out from the first flow rate control means; A pressure detecting means for detecting a pressure inside the accumulating means, a second flow rate controlling means for causing a desired use flow rate of the mixed gas supplied from the accumulating means to flow out, and the pressure adjusting means with respect to the pressure adjusting means. A pressure suitable for the supply of gas to one flow rate control means is indicated as the set pressure, and the flow rates of the various gases are set so that the various gases after mixing have a desired concentration. The flow rate is determined according to a desired use flow rate and the detection result of the pressure detection means, the determined flow rate is indicated to the first flow rate control means by a digital signal corresponding to the set flow rate, and the second flow rate is determined. Control means for instructing the control means on the desired flow rate of the mixed gas.
[0015]
According to a second aspect of the present invention, there is provided the gas mixing apparatus according to the first aspect, wherein when the control means instructs the set flow rate to the first flow rate control means, the flow rates of the various gases are reduced. It is characterized by instructing the flow rate to be gradually increased to the set flow rate.
[0016]
According to a third aspect of the present invention, in the gas mixing apparatus according to the first or second aspect, the control means includes the concentration detection means for accurately detecting the concentration of a predetermined type of gas in the mixed gas. The concentration of the gas is checked, the indicated flow rate is corrected and stored so that the result matches the desired concentration of the predetermined gas, and the stored flow rate is indicated as the set flow rate. It is characterized by.
[0017]
According to a fourth aspect of the present invention, there is provided the gas mixing apparatus according to the first or second aspect, wherein the control means instructs a set flow rate of the various gases to be instructed to the first flow rate control means from a high flow rate range to a low flow rate. With respect to each flow rate range when changed to a region, the detection result detected by the concentration detecting means for accurately detecting the concentration of the predetermined type of gas in the mixed gas and the desired type of the predetermined type of gas Control means for storing data obtained by correcting the correspondence between the set flow rate and a digital signal indicating the set flow rate so that the concentrations coincide with each other, and instructing the set flow rate to the first flow rate control means based on the data It is characterized by being.
[0018]
According to a fifth aspect of the present invention, there is provided the gas mixing device according to any one of the first to fourth aspects, wherein the accumulating means has a mesh of a predetermined material between an inlet and an outlet of the mixed gas. It is characterized by being a storage means attached.
[0019]
A sixth aspect of the present invention is the gas mixing apparatus according to any one of the first to fifth aspects, wherein the control means instructs the set flow rate to be instructed to the first flow rate control means in a high flow rate range. Only a predetermined flow rate is set, and the suspension / resumption of gas mixing is instructed according to the detection result of the pressure detection means.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a gas mixing apparatus according to an embodiment of the present invention.
[0021]
In this figure, 1A and 1B are gas lines to which different types of gas A and gas B are supplied. 2A and 2B are open / close valves provided in the gas lines 1A and 1B, respectively, and open and close the gas lines 1A and 1B. 3A and 3B are auto pressure regulators that adjust the pressures of the gas A and the gas B in the gas lines 1A and 1B based on the instruction signal from the control unit 5 received via the electric system line 4.
[0022]
The control unit 5 includes an input device and a storage device that receive instructions from the outside, and each of the auto pressure regulators 3A and 3B, the pneumatic valve 6 and the like based on the instructions and a control program stored in the storage device. A signal for controlling the device is transmitted in the form of an electric signal or an air signal. Details of the operation performed by the control unit 5 will be described later.
[0023]
The pneumatic valve 6 opens and closes the gas flow before and after the digital mass flow controllers 8A and 8B. The pneumatic valve 6 controls the control unit 5 via an instrument gas line 7 that transmits instrument gas as an air signal. Controlled by
[0024]
The digital mass flow controllers 8 </ b> A and 8 </ b> B are mass flow controllers that give a voltage signal indicating a set flow rate to a sensor provided in a flow rate control unit as a digital signal, and control the flow rates of gas A and gas B. Here, the voltage signal that indicates the flow rate is determined by the control unit 5 based on a calibration curve that indicates the relationship between the flow rate and the voltage signal. The calibration curve is stored in the storage device in the control unit 5, but correction is appropriately made because the accuracy of the sensor of the mass flow controller varies. The correction of the calibration curve will be described later.
[0025]
9 is a mixer which stirs the gas A and the gas B which flowed into one gas line. A buffer tank 10 temporarily accumulates the mixed gas. A stainless steel wire mesh (SUS mesh) 10 s is attached to the center of the buffer tank 10 perpendicularly to the gas traveling direction, and the gas line enters a predetermined position inside. Reference numeral 11 denotes a pressure indicator for detecting the pressure in the buffer tank 10, and the detected value is transmitted to the control unit 5 in the form of an electric signal. Reference numeral 12 denotes a mass flow controller for controlling the outflow amount of the mixed gas generated in accordance with the use flow rate of the mixed gas instructed by the control unit 5.
[0026]
Reference numeral 13 denotes a manual valve for conducting or blocking the flow of the mixed gas by opening and closing. Reference numeral 14 denotes a variable flow rate manual valve which supplies a predetermined amount of mixed gas to the analyzer 15. The analyzer 15 includes a concentration measuring device that precisely measures the concentration of gas A, and has a function of monitoring the measured concentration. This analyzer 15 is used in calibration curve correction described later. For this reason, the calibration curve is removed after completion of the calibration curve, or the supply of the mixed gas is stopped by the manual valves 13 and 14, and the concentration measurement is terminated.
[0027]
Next, the operation of the gas mixing apparatus according to the above embodiment will be described. First, the on-off valves 2A and 2B are opened, and supply of gas A and gas B is started. At this time, according to an instruction signal from the control unit 5, the auto pressure regulator 3A, so that the pressure of the gas A and the gas B becomes a working pressure (hereinafter referred to as “set pressure”) in consideration of the pressure resistance of the digital mass flow controllers 8A, 8B. 3B is controlled. Thereby, the pressures of the gas A and the gas B supplied to the inlets of the digital mass flow controllers 8A and 8B are adjusted.
[0028]
When the set concentration of gas A is input to the control unit 5 to instruct the start of gas mixing, all pneumatic valves 6 are opened by an air signal from the control unit 5. At the same time, an electrical signal instructing the digital mass flow controllers 8A and 8B to start flowing gas A and gas B at a constant flow rate (hereinafter referred to as “set flow rate”) having the set concentration gradually. A gas signal is transmitted from the control unit 5 in the form of a digital signal, and gas mixing is started.
[0029]
The mixed gas A and gas B are mixed by the mixer 9 and flow into the buffer tank 10. In the buffer tank 10, the concentration of the mixed gas at the inlet and the mixed gas at the outlet is made uniform by the stainless steel wire mesh 10s.
[0030]
At this time, the manual valves 13 and 14 are opened, and the mixed gas is supplied to the analyzer 15. Then, since the deviation between the precisely measured concentration of the gas A after mixing and the set concentration at that time can be known, the electric signal instructing the set flow rate to the digital mass flow controller 8A or 8B is corrected based on this.
[0031]
Further, the calibration curve is corrected by correcting the set flow rate instruction as described above while changing the set flow rate in the digital mass flow controller 8A or 8B from the low flow rate range to the high flow rate range. Then, the corrected calibration curve is stored in the storage device in the control unit 5.
[0032]
Thereby, in the subsequent generation of the mixed gas, the corrected calibration curve can be used for the flow control of the gas A and the gas B in the digital mass flow controllers 8A and 8B. Therefore, more accurate mixing can be performed without requiring monitoring by the analyzer 15, and a mixed gas having a desired set concentration can be obtained. Then, by the flow rate control of the mass flow controller 12 based on the instruction from the control unit 5, the mixed gas corresponding to the desired usage flow rate is caused to flow out.
[0033]
Thereafter, similarly to the above, the pressures of the supplied gas A and gas B are controlled to the set pressure by the auto pressure regulators 3A and 3B, and according to the flow rate used and the pressure in the buffer tank 10 detected by the pressure indicator 11. By controlling the digital mass flow controllers 8A and 8B, a mixed gas having a desired set concentration is generated.
[0034]
When the pressure in the buffer tank 10 detected by the pressure indicator 11 reaches a predetermined upper limit, all the pneumatic valves 6 are closed, the digital mass flow controllers 8A and 8B are fully closed, and mixing is interrupted. To do.
[0035]
Further, in the gas mixing device according to the present embodiment, the set flow rate may be set to a certain point in the high flow rate range where the flow rate control accuracy of the digital mass flow controllers 8A and 8B is relatively high, and gas mixing may be performed. In this case, when the pressure in the buffer tank 10 detected by the pressure indicator 11 reaches a predetermined upper limit, all the pneumatic valves 6 are closed, and at the same time, the digital mass flow controllers 8A and 8B are fully closed to perform mixing. When the mixing is started again, all the pneumatic valves 6 are opened, and at the same time, the operation of gradually starting to flow the gases A and B at the set flow rates is repeated. Thereby, since gas can be mixed under flow control with high accuracy, a mixed gas with higher mixing accuracy can be generated.
[0036]
【The invention's effect】
As described above, according to the present invention, since the set flow rates of various gases are indicated by digital signals, the linearity of the correspondence between the flow rates and the signals indicating them is improved. As a result, it is possible to avoid a decrease in mixing accuracy due to the difference in accuracy of each flow rate control means, and since the flow rate instruction signal is transmitted in a digital signal format, it is transmitted compared to the case where the flow rate is indicated by an analog signal. The effect that there is little loss is acquired.
[0037]
Further, by adjusting the pressure of various gases supplied by the pressure adjusting means and then mixing, it is possible to prevent unexpected flow rate fluctuations of various gases. In particular, according to the second aspect of the invention, the flow rate commanded at the beginning of gas mixing is not the set flow rate itself, but the flow rate command is given so as to increase gradually. The flow rate is not disturbed. By these, the effect that the flow of gas can always be kept in a stable state and the mixing accuracy can be improved is obtained.
[0038]
Furthermore, according to the third aspect of the invention, since the flow rate instruction is corrected by detecting the concentration of the gas after mixing, accurate flow rate control satisfying a desired set concentration is possible. According to the more advanced invention of claim 4, by acquiring data for the correction in each flow rate region, it is possible to detect the concentration of gas after mixing in subsequent mixing. The effect that accurate flow control can be performed is obtained.
[0039]
In addition, according to the fifth aspect of the present invention, when the mixed gas is once accumulated and discharged from the accumulating means, the concentration of various gases in the mixed gas is made uniform by passing the mesh of the mesh. . Thereby, even if the set flow rate changes due to fluctuations in the use flow rate, etc., a mixed gas with high mixing accuracy can be obtained.
[0040]
According to the sixth aspect of the present invention, the flow rate control means performs the flow rate control in a high flow rate range where the accuracy is good, and the amount of the mixed gas produced is adjusted by interrupting / resuming the mixing. As a result, gas can be mixed under conditions where the flow rate control accuracy is good, and the effect of improving the mixing accuracy can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a gas mixing apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a first configuration example of a conventional gas mixing device.
FIG. 3 is a block diagram showing a second configuration example of a conventional gas mixing device.
[Explanation of symbols]
3A, 3B Auto pressure regulator 5 Control unit 8A, 8B Digital mass flow controller 10 Buffer tank 10s Stainless steel wire mesh 11 Pressure indicator 12 Mass flow controller 15 Analyzer

Claims (6)

In a gas mixing device that mixes different types of gases,
Pressure adjusting means for causing various gases to be supplied at a set pressure to flow out; and
First flow rate control means for controlling the various gases flowing out from the pressure adjusting means to flow at a set flow rate indicated by a digital signal;
Accumulation means for once accumulating and supplying a mixed gas obtained by mixing the various gases flowing out from the first flow rate control means;
Pressure detection means for detecting the pressure inside the storage means;
Second flow rate control means for causing a desired use flow rate of the mixed gas supplied from the accumulation means to flow out;
The pressure adjusting means is instructed as the set pressure a pressure suitable for the gas supply to the first flow rate control means, and the various gas flow rates for the various gases after mixing to have a desired concentration Is determined according to the desired flow rate and the detection result of the pressure detection means, the determined flow rate is indicated to the first flow rate control means by a digital signal corresponding to the set flow rate, and the second flow rate is determined. And a control means for instructing the desired use flow rate of the mixed gas to the flow rate control means. The control means instructs the first flow rate control means to gradually increase the flow rate of the various gases from a low flow rate to the set flow rate when instructing the set flow rate. The gas mixing device according to claim 1. The gas mixing device according to claim 1 or 2,
The control means checks the concentration of the predetermined type of gas by the concentration detection means for accurately detecting the concentration of the predetermined type of gas in the mixed gas, and the result and the desired type of the desired type. A gas mixing apparatus characterized by correcting and storing an instructed flow rate so that the gas concentrations match, and instructing the stored flow rate as the set flow rate. The gas mixing device according to claim 1 or 2,
The control means is a predetermined one of the mixed gases with respect to each flow range when the set flow rate of the various gases instructed to the first flow control means is changed from a high flow rate range to a low flow rate range. Correspondence between the set flow rate and the digital signal indicating it so that the detection result detected by the concentration detecting means for accurately detecting the concentration of the gas of the type matches the desired concentration of the predetermined type of gas. A gas mixing apparatus characterized by being a control means for storing corrected data and instructing the set flow rate to the first flow rate control means based on the data. 5. The storage unit according to claim 1, wherein the storage unit is a storage unit in which a mesh of a predetermined material is attached between an inlet and an outlet of the mixed gas. Gas mixing device. In the gas mixing device according to any one of claims 1 to 5,
The control means sets the set flow rate to be instructed to the first flow rate control means only to a predetermined flow rate in a high flow rate range, and instructs suspension / resumption of gas mixing according to a detection result of the pressure detection means. A gas mixing device characterized by:

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