JPS618127A - Gas blending apparatus - Google Patents

Abstract

PURPOSE:To allow a mixing ratio to follow the variation in load while holding said mixing ratio to a predetermined one, by providing a pressure detection means in a buffer tank and performing the supply or stoppage of gas to said tank when the internal pressure of the tank reaches a predetermined value. CONSTITUTION:When the pressure in a buffer tank 50 reaches lower limit one in such a state that a constant flow amount is subjected to ON/OFF control, control valves 12, 22 are opened and blending is started in a set flow amount and, when said pressure in the buffer tank 50 reaches upper limit one, the control valves 12, 22 are closed. As a result, the flow amount of a flow meter is turned ON/OFF at a definite value to perform blending and, therefore, only the cycle of ON/OFF is changed by the variation in load and the correspondence to a wide range of the variation in load can be performed. Because the supply of both gases rises simultaneously, if delays of both gases are coincided, a transitional blending ratio can be kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION Entohoku TECHNICAL FIELD The present invention relates to a gas blending device suitable for use in blending gas flowing through a first flow path and gas flowing through a second flow path at a predetermined ratio.

Figure 5 is a block diagram for explaining an example of a gas blending device that controls the mixing ratio when a first fluid (gas) and a second fluid (gas) are mixed and used. During,
10 is a first fluid (gas) flow path, 20 is a second fluid (gas)
Flow path, 30 is a mixed fluid (gas) of the first fluid and the second fluid
A gas welding machine, a gas burner, etc. are connected to an unillustrated tip of the mixed fluid flow path 30 in the flow path. 11 is a first fluid flow meter, 12 is a first fluid control valve, 21 is a second fluid flow meter, 22 is a second fluid control valve,
40 is a gas blender (comparison controller), flowmeters 11 and 21 generate signals proportional to their respective flow rates, the output signals of these flowmeters 11 and 21 are compared by gas blender 40, and the first fluid and the first fluid are The control valves 12 and 2 are connected so that the volume ratio of the two fluids becomes a predetermined value.
The opening degree of No. 2 is controlled. In the above gas blending device, the flow rate of both gases is controlled to match the set flow rate, and the target value is given by setting the reference voltage built in the blender 40 as a ratio i. For example, by changing the settings of a potentiometer on the mask side, the flow rate is controlled while keeping the mixing ratio constant.

However, in the above blending device, if the target value is kept constant, the flow becomes constant flow control, and it cannot follow the load due to severe fluctuations. Therefore, the target value is given from the outside and the target value is set. need to be controlled like this.

Furthermore, when the flow rate is small and outside the flow rate range for which accuracy is guaranteed, the accuracy of the flow rate decreases, resulting in a problem that the actual mixing ratio decreases significantly.

-Hiroshi This invention was made in view of the above-mentioned circumstances,
In particular, the purpose of this invention is to provide a gas blending device that can follow changes in load while maintaining the mixing ratio at a predetermined ratio.

Fig. 1 is a configuration diagram for explaining an embodiment of the gas blending device according to the present invention, and in the figure, 50 indicates the mixed gas flow path 3.
Buffer tanks 60U and 60L provided in the buffer tank 50 are pressure switches, 60U detects the upper limit set pressure in the buffer tank 50, and 60L detects the lower limit set pressure. Therefore, in this embodiment, the constant flow rate is controlled by 0N10FF, and when the pressure inside the buffer tank 50 reaches the lower limit pressure, the control valve [2.22] opens and blending starts at the set flow rate. When the second pressure limit is reached, the control valve 12.22 closes. Therefore, according to this embodiment, the flow rate of the flowmeter is 0N10 F at a certain constant value.
Since it is blended with F, 0N1 due to load fluctuation.
A wide range of load fluctuations can be accommodated simply by changing the 0FF cycle. Furthermore, since the supply of both gases starts at the same time, it is possible to keep the transient blend ratio constant if the delays of both gases match. However, according to this embodiment, since the flow rate setting value must be set to the maximum value of the expected flow rate, the flow rate becomes large, and therefore the buffer tank requires a somewhat large capacity.

FIG. 2 is a diagram showing load fluctuations in the embodiment shown in FIG. 1, where (a) shows load fluctuations in flow rate, and FIG. 2(b) shows load fluctuations in pressure. However, the 0N1 shown in Figure 1 above
In the 0FF control method, since the flow rate is large, the gain of the control section is high, and when the load flow rate is large, the frequency of 0N10FF is high, and conversely, when the load flow rate is small, the frequency is low.

That is, there is a problem in that the opening time of the control valve that operates the flow meter is short, and the blend ratio is affected by differences in the responses of the control valve revs. If a buffer tank is not installed, or if a buffer tank is installed but the capacity is small, set the upper and lower limit pressure switches to 0N10F.
The frequency of F becomes even thicker.

FIG. 3 is a configuration diagram for explaining another embodiment of the gas blending device according to the present invention, in which 70 is a pressure detector for detecting the pressure in the mixed gas flow path 30, and 80 is a converter. This embodiment is suitable for gas blending in which a buffer tank cannot be attached, and the target value is changed in accordance with the pipe pressure after mixing. That is, in this embodiment, the target value is controlled according to the pressure on the load side. Therefore, when the pressure is low, the flow rate is controlled to increase, and when the pressure increases, the flow rate is decreased. It is a kind of pressure control that works. In other words, this embodiment further improves the drawbacks of the embodiment shown in FIG. A converter 80 is provided that outputs a target value that is inversely proportional to the pressure signal from the detector 70, and the target value is changed according to the piping pressure after mixing, and when the target value is below a certain level, the target value is changed. The value is set to zero and the operation is stopped.

Note that the output signals from the flowmeters 11 and 21 described above are compared with the target value given by setting the ratio of the reference voltage, so they are output as analog values, but when they are transmitted as digital signals. converts this digital signal into an analog signal and outputs it as an analog signal. Furthermore, since fluids differ depending on temperature and pressure, if these are corrected and output as a mass flow signal, a load flow with a more accurate blend ratio can be obtained. Further, in the above description, a two-component blender has been described, but the present invention can be similarly applied to a multi-component blender.

FIG. 4 is a diagram showing load fluctuations in the embodiment shown in FIG. 3, where (a) shows flow rate load fluctuations, and ('b) shows pressure load fluctuations.

Effects As is clear from the above explanation, according to the present invention, it is possible to follow load fluctuations while keeping the mixing ratio at a predetermined value. Further, there are advantages such as being able to deal with a wide range of flow rates with less error.

[Brief explanation of drawings]

FIG. 1 is a block diagram for explaining an embodiment of a gas blending device according to the present invention, FIG. 2 is a load characteristic diagram of the embodiment shown in FIG. 1, and FIG. FIG. 4 is a load characteristic diagram of the embodiment shown in FIG. 3, and FIG. 5 is a configuration diagram showing an example of a conventional gas blending device. 10.2G... Gas flow path, 30... Mixed gas flow path,
40... blender, 50... buffer tank, 60
U. 60L...Pressure switch, 70...Pressure detector, 8
0...Converter. Figure 1 Figure 2 (a) t□ (b) t□ Figure 3

Claims (3)

[Claims] (1) In a gas blending device that mixes gas in a second flow path with respect to gas in a first flow path at a predetermined ratio, a buffer tank is provided in the mixed gas flow path, and a pressure detection means is provided in the tank. A gas blend, characterized in that the supply of gas to the buffer tank is started when the pressure within the buffer tank reaches a predetermined lower limit value, and stops when the pressure within the buffer tank reaches a predetermined upper limit value. Device. (2) In a gas blending device that mixes gas in a second flow path with respect to gas in a first flow path at a predetermined ratio, the mixed gas flow path is equipped with a pressure sensing means, and the output of the pressure sensing means is provided. A gas blending device comprising a converter that outputs a target value that is inversely proportional to a signal, and the target value is changed according to the gas pressure after mixing. (3) The mixing is stopped when the target value reaches a predetermined value or less.
The gas blending device according to item 2).