JP2004157019A - Fine differential pressure generating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fine differential pressure generating device capable of generating inexpensive and stable fine differential pressure. <P>SOLUTION: This device has a fluid supply source 50 capable of supplying a fluid at a prescribed pressure, a conduit 60 having one end connected thereto, a leak type pressure reducing valve 70 provided in the middle of the conduit, a first vessel 10 wherein the pressure reducing valve and a partial conduit on the downstream side thereof are stored inside and the fluid is leaked to the inside from the leak type pressure reducing valve, a second vessel 20 connected to the other end of the conduit, two branched pipes 65, 66 stored in the first vessel, connected in the branched state to parts of the pipe on the downstream side of the leak type pressure reducing valve, and connected respectively to the HI pressure side and the LO pressure side of a fine differential pressure gage to be calibrated, and connection pipes 81, 82 connecting in the communicating state the two vessels and equipped with an atmospheric opening part 31 on a part thereof. A pressure loss generation part 63 is formed between the branched pipes. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fine differential pressure generating device used when calibrating a fine differential pressure gauge.
[0002]
[Prior art]
2. Description of the Related Art In recent years, the use of a fine differential pressure transmitter (hereinafter, simply referred to as a “fine differential pressure gauge”) for measuring a small differential pressure in air conditioning equipment such as a clean room has increased. The fine differential pressure used for calibration of such a fine differential pressure gauge generally refers to a range from 1 Pa (Pascal) to 3000 Pa. The pressure of a normal gas measured conventionally is in the range of 5 kPa to 10 MPa.
[0003]
2. Description of the Related Art Generally, a device for generating a differential pressure that serves as a reference for calibrating the output characteristics of a differential pressure gauge has been conventionally used.
[0004]
As an example of such a small differential pressure generating device, a small differential pressure generating device as shown in FIG. 2 (hereinafter, referred to as a “first small differential pressure generating device”) is known. The first fine differential pressure generating device 100 has a configuration in which one closed container 110 is defined by two partitions in a closed space 111 and 112 and only one closed space 111 is connected to a pump 130 via a communication path. Have. The pipes 121 and 122 connected to each closed space are connected to the HI pressure side inlet 141 and the LO pressure side inlet 142 of the micro differential pressure gauge 140 to be calibrated, respectively. Before the pump is driven, the valve 113 is opened to equalize the pressure in both the sealed spaces 111 and 112, and then the valve 113 is closed and the cylinder 131 of the pump 130 is moved (see a two-dot chain line in the figure). , The volume in the enclosed space 111 to which the pump 130 is connected is slightly reduced, and based on Boyle-Charles' law, the pressure difference between the pressure in the other enclosed space 112 and the pressure in the one enclosed space 111 is slightly reduced. To produce Then, a small differential pressure is applied to the small differential pressure gauge 140 connected via the pipes 121 and 122 extending individually from the above-mentioned closed spaces 111 and 112.
[0005]
On the other hand, another conventional micro differential pressure generating device (hereinafter referred to as "second micro differential pressure generating device") forms a flow path in the radial direction of a rotatable disk and fills the flow path with gas. By rotating the disk in this state, centrifugal force is applied to the gas in accordance with the distance from the center of the disk. Then, the rotation of the disk causes the gas to move outward in the disk radial direction, so that the pressure at the center of the disk is lower than the pressure at the circumference of the disk. Then, by taking out the pressure at the center of the disk and the pressure at the circumference of the disk separately, a small differential pressure is generated using this pressure difference, and the output calibration of the small differential pressure gauge is performed using the small differential pressure. (For example, see Patent Document 1).
[0006]
Still another conventional differential pressure generating device (hereinafter referred to as "third differential pressure generating device") uses an optical structure to read the height of the liquid, and based on the density and height of the liquid, This is to read the slightly generated differential pressure. In this method, a differential pressure standard device and a micro differential pressure generating device are used as the same device, and a micro differential pressure is accurately measured and generated using a U-tube and an optical interferometer (for example, Patent Document 2). reference.).
[0007]
[Non-patent document 1]
Yonehiko Akinaga, "Investigation and Research on Measurement Standards for Low Pressures", Report of Metrology Institute, Vol. 48, No. 2, 1999
[Non-patent document 2]
Yonehiko Yonenaga, "Survey and Research on Measurement Standards for Low Pressure", Report of Metrology Institute, Vol. 48, No. 2, 1999 (No. 200, separate volume, paragraphs 95-96, Fig. 8)
[Problems to be solved by the invention]
The above-mentioned first slight differential pressure generating device is formed in a state where the closed spaces are individually partitioned by partition walls. When generating a differential pressure with a pump, only one closed space is compressed, but it is difficult to make such a compression process an ideal adiabatic compression such as a Carnot cycle. It is inevitably affected by the rise in temperature.
[0008]
That is, when the ambient temperature changes by 0.01 ° C., the pressure generally changes by 3 Pa. However, under normal pressure measurement, such a change in pressure does not cause an error that affects the pressure measurement. However, this becomes an error factor that has a considerable effect under the measurement of the slight differential pressure as described above.
[0009]
As described above, since the pressure changes by 3 Pa only by changing the temperature by 0.01 ° C., the first fine differential pressure generating device can accurately calculate the pressure according to the fluctuation amount of the volume of the one-sided container. A small differential pressure cannot be generated.
[0010]
Further, the second micro differential pressure generating device can adjust the micro differential pressure generated by changing the angular velocity of the disk. A special structure is required to prevent rotation unevenness from occurring due to abutment or the like, which has a disadvantage that the structure is complicated and the cost is high.
[0011]
In addition, the third differential pressure generating device is a large-scale facility because it uses an optical interferometer, and is more expensive than the first and second differential pressure generating devices described above. Therefore, its use is limited to research facilities and the like, and such a small differential pressure generator is not suitable for mass-supply to the general market.
[0012]
SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive micro differential pressure generator capable of generating a stable micro differential pressure.
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a minute differential pressure generating device according to claim 1 of the present invention includes a fluid supply source capable of supplying a fluid at a predetermined pressure, and a pipeline having one end connected to the fluid supply source. The leak type pressure reducing valve provided in the middle of the pipe, the leak type pressure reducing valve, and a part of the downstream side pipe of the pressure reducing valve are housed therein, and the fluid is leaked from the leak type pressure reducing valve to the inside. , A second container connected to the other end of the conduit, and a branch connected to a part of the conduit downstream of the leak-type pressure reducing valve housed in the first container to be calibrated. Two branch pipes that can be connected to the HI pressure side and the LO pressure side of the differential pressure gauge, respectively, and a connection pipe line that connects and connects the first container and the second container and has a part that is open to the atmosphere, A pressure loss generating portion is formed between the two branch pipes of the pipeline.
[0014]
A leak-type pressure reducing valve is provided on the inlet side of the pipe in a state housed in the first container, and the outlet side of the pipe is connected to the second vessel and establishes a communication passage between the second vessel and the first vessel. Is open to the atmosphere. That is, the outlet side of the pipe is not directly opened to the atmosphere, but is opened to the atmosphere via the second container and the connection pipe. In addition, the fluid leaked into the first container in the leak type pressure reducing valve is discharged to the atmosphere via a communication path that functions as a throttle. That is, the fluid leaked by the leak type pressure reducing valve fills the first container, a part of the fluid moves to the second container via the communication passage, and the remaining part is discharged to the atmosphere from the atmosphere opening portion of the connection pipe. It is supposed to be. That is, the fluid discharged from the leak type pressure reducing valve and the fluid discharged from the pipe outlet are filled in the first container and the second container, respectively, and after both containers are completely filled with these fluids, the atmosphere opening portion is opened. The fluid is discharged from. Thereby, the first container and the second container complement each other in the process of filling with the fluid, and the fluid can be more stably discharged to the atmosphere as compared with the case where the fluid is separately discharged to the atmosphere. In addition, when the influence from the atmosphere is received from the leak type pressure reducing valve or the pipe outlet, the influence from the atmosphere is not separately received, and the influence is received through the common atmosphere opening part. And the first vessel, the second vessel, and the connecting line cooperate to absorb different types of influence from the atmosphere.
[0015]
Therefore, the leak-type pressure reducing valve that controls the pressure while leaking the gas by the differential pressure from the atmospheric pressure is not directly affected by the atmospheric pressure fluctuation, and the pressure at the pipe inlet side is stabilized, and the pipe outlet side Pressure also stabilizes. This allows a constant flow rate of fluid to flow through the pipe without being affected by the external atmosphere. Then, a stable pressure loss is generated in the pressure loss generating section due to the viscosity of the gas, so that a more stable constant fine differential pressure can be generated upstream and downstream of the pressure loss generating section.
[0016]
Further, a slight differential pressure generating device according to a second aspect of the present invention is characterized in that, in the slight differential pressure generating device according to the first aspect, the pressure loss generating unit includes a pressure reducing means and a flow rate adjusting means. .
[0017]
Since the pressure in the pipe is sufficiently reduced by the pressure reducing means and the flow rate is adjusted by the flow rate adjusting means, the pressure difference generating section always generates the fine differential pressure accurately.
[0018]
Further, according to a third aspect of the present invention, there is provided the micro differential pressure generating device according to the first or second aspect, wherein the connecting pipe for communicating the first container and the second container is provided. A third container is interposed in a predetermined portion, and an air opening portion is provided in the third container in place of the air opening portion according to claim 1.
[0019]
By providing the third container, the moderate pressure fluctuation received from the surrounding atmosphere is mainly absorbed by the third container, and the effect that cannot be completely absorbed by the third container is absorbed by the first container or the second container serving as a buffer. I do. In addition, since the connecting conduits between the third container, the first container, and the second container also serve as throttles, abrupt pressure fluctuations received from the surrounding atmosphere are absorbed by these throttles. Therefore, as compared with the case where the third container is not provided, the pressure loss generating section is further less affected by the atmosphere, and a more stable generation of a small differential pressure is possible.
[0020]
Also, in the fine differential pressure generating device according to claim 4 of the present invention, in the fine differential pressure generating device according to claim 3, the volume of the third container is smaller than the volumes of the first container and the second container. Features.
[0021]
Since the volume of the third container is smaller than the volumes of the first container and the second container, the response of the pressure feedback system formed between the second container and the first container via the connection pipe and the third container Does not adversely affect sex.
[0022]
In addition, since the volumes of the first container and the second container are larger than those of the third container, the third container and the connection conduit connected to the third container out of the gradual pressure fluctuation and the pulsating pressure fluctuation received from the surrounding atmosphere. The pressure fluctuation that cannot be absorbed by the pressure can be reduced.
[0023]
Therefore, the pressure drop in the pressure loss generating section is stably performed, and a slight differential pressure can be stably generated in the pressure loss generating section without being directly affected by the external atmosphere.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a slight differential pressure generating device according to an embodiment of the present invention will be described with reference to the drawings.
[0025]
The fine differential pressure generating device 1 according to one embodiment of the present invention includes a tank 50 filled with nitrogen, a pipe (pipe) 60 having one end connected to the tank 50, and a leak provided in a part of the pipe 60. A first container 10 that houses therein a leak-type pressure reducing valve 70, a leak-type pressure reducing valve 70, and a partial pipe downstream of the pressure reducing valve 70, a second container 20 connected to the other end of the pipe 60, The third container 30 is connected to the first container 10 and the second container 20 via the first communication path (connection pipe) 81 and the second communication path (connection pipe) 82, respectively.
[0026]
In the pipe 60, two pressure reducing valves 51 and 52 are arranged in series between the tank 50 and the leak type pressure reducing valve 70, and are housed in the first container 10 on the downstream side of the leak type pressure reducing valve 70. In this state, the first valve 61, the second valve 62, and the third valve 63 are arranged in series from the upstream to the downstream of the pipe. Further, from the pipe 60, an HI pressure supply pipe 65 is branched from an upstream side of the pipe with a third valve interposed therebetween, and an LO pressure supply pipe 66 is branched from a downstream side of the pipe, and each of them projects outside the first container. ing. The HI pressure supply pipe 65 and the LO pressure supply pipe 66 are connected to the HI pressure side inlet 91 and the LO pressure side inlet 92 of the differential pressure gauge 90 to be calibrated, respectively. It is designed to apply pressure. The HI pressure supply pipe 65 and the LO pressure supply pipe 66 are also connected to a reference pressure gauge 95, and the pressure measured by the reference pressure gauge 95 at the time of fine differential pressure calibration is confirmed. However, the calibration of the differential pressure gauge 90 is performed.
[0027]
Note that FIG. 1 shows a state in which the fine differential pressure gauge 90 and the reference pressure gauge 95 to be calibrated are actually connected to the HI pressure supply pipe 65 and the LO pressure supply pipe 66.
[0028]
On the other hand, from the third container 30, a pipe 31 for opening to the atmosphere having one end open is extended. The pipe 60, the first communication path 81, the second communication path 82, the HI pressure supply pipe 65, and the LO pressure supply pipe 66 have an inner diameter of, for example, about 5 mm, and the atmosphere opening pipe 31 has, for example, about 5 mm. It has an inner diameter of about 2.5 mm. That is, the pipe 60, the first communication path 81, the second communication path 82, the HI pressure supply pipe 65, and the LO pressure supply pipe 66 are pipes having the same inner diameter, and the atmosphere opening pipe 31 is A pipe having an inner diameter smaller than the pipe. Further, the length of the pipe 60 is, for example, 0.5 m, the length of the first communication passage 81 is, for example, 2.0 m, the length of the second communication passage 82 is, for example, 2.5 m, and the length of the atmosphere-opening pipe 31 is, for example. For example, it is about 0.3 m.
[0029]
On the other hand, the first container 10 has a volume of, for example, about 200 liters, the second container 20 has a volume of, for example, about 120 liters, and the third container 30 has a volume of, for example, about 0.8 liter. I have. That is, the volume of each container is smaller than that of the first container 10 and the second container 20.
[0030]
The leak type pressure reducing valve 70 housed in the first container is a known type. A diaphragm is provided inside the pressure reducing valve, and a part of the gas (fluid) is urged by a spring by the spring to reduce a part of the gas (fluid). The gas is discharged into the chamber 10 so that a stable pressure reduction is always performed. That is, the gas discharged from the leak-type pressure reducing valve 70 fills the first container 10 and then moves to the third container via the first communication passage 81, and thereafter, the second container 20 is not filled with the gas. In such a case, it moves to the second container 20 and the remaining part is discharged from the atmosphere opening pipe 31. On the other hand, the gas discharged from the leak type pressure reducing valve 70 to the second container 20 via the pipe 60 moves to the third container via the second communication path 82, and thereafter, the first container 10 is filled with the gas. If not, a part moves to the first container 10 and the remaining part is discharged from the atmosphere opening pipe 31. That is, the gas discharged to the atmosphere is discharged from the common atmosphere opening pipe 31 after all of the first to third containers 30 to 30 are filled with the gas.
[0031]
The first valve 61 is a fixed throttle needle valve, and the first valve 61 reduces the pressure in the pipe. The second valve 62 is a flow rate adjusting needle valve that can variably control the flow rate of the fluid in the pipe. The third valve 63 plays the role of a throttle as a pressure loss generating unit for generating a pressure drop between the two branch pipes. The third valve (pressure loss generating section) 63 is formed of an orifice in the case of the present embodiment.
[0032]
It should be noted that the pressure loss generating section may not be constituted by a special throttle such as an orifice, but may be constituted by a simple pipe. Even in this case, if the fluid is a gas having a small molecular weight, such as hydrogen or helium, a pressure loss occurs in this part due to viscous resistance between the pipe wall and the pressure loss generating part that generates a slight differential pressure. Performs sufficient functions. Further, there is no problem even if the pressure loss generating section is constituted by a normal needle valve.
[0033]
Subsequently, a calibration procedure and operation of the differential pressure gauge 90 using the differential pressure generating device 1 will be described.
[0034]
First, as a preliminary preparation, a differential pressure gauge 90 and a reference pressure gauge 95 for calibration are attached to the differential pressure generating device 1, nitrogen is supplied from the tank 50, and about 0.1 MPa is supplied to a pipe inlet of the differential pressure generating device 1. Of nitrogen. In the present embodiment, the pressure in the tank 50 is 14 MPa, and the pressure is reduced to 1 MPa by the pressure reducing valve 51 downstream thereof. Further, the pressure is reduced to 0.1 MPa by the pressure reducing valve 52 on the downstream side.
[0035]
Then, the second valve 62 of the pipe connected to the tank 50 is closed.
[0036]
Subsequently, the second valve 62 is gradually opened to reach a vicinity of a predetermined pressure. Since the second valve 62 is a flow control valve, by adjusting this, the pressure in the pressure loss generating section can be brought close to the gauge pressure necessary for generating a slight differential pressure.
[0037]
Thereby, a part of the nitrogen is discharged into the first container by the leak type pressure reducing valve 70 in the first container, and the pressure of 0.1 MPa in the pipe on the upstream side of the leak type pressure reducing valve is reduced in the pipe on the downstream side of the leak type pressure reducing valve. The pressure is reduced to 0.05 MPa.
[0038]
Subsequently, fine adjustment of a slight differential pressure (a desired pressure within 1 Pa to 3000 Pa) to be generated by the third valve 63 is performed. That is, the gas having a pressure of 50 kPa at the pipe inlet by the first valve 61 is sufficiently reduced in pressure through the first valve 61, the second valve 62, and the third valve 63, and the upstream pressure of the third valve 63 is reduced. The pressure difference between the pressure and the downstream pressure is stably generated in the range of 1 Pa to 3000 Pa. Note that all the pressures up to now are gauge pressures. Then, the fine differential pressure of the fine differential pressure gauge 90 is adjusted based on the fine differential pressure. At the time of the fine differential pressure adjustment, the adjustment operation is performed while checking the pressure display of the reference pressure gauge 95.
[0039]
In generating a slight differential pressure in the pressure loss generating section including the third valve 63, as is clear from the above-described configuration, the outlet side of the pipe 60 is not directly open to the atmosphere, and the second container 20 and the communication path 82 , And through the third container 30. Further, the nitrogen leaked by the leak-type pressure reducing valve 70 fills the first container 10, and a part of the nitrogen moves to the second container 20 via the first communication passage 81, the third container 30, and the second communication passage 82. The remaining part is discharged to the atmosphere from the atmosphere opening pipe 31 of the third container 30.
[0040]
That is, once the gas that has passed through different exhaust paths fills the first container 10 and the second container 20 and finally fills the common third container 30, the gas saturated here is first discharged to the atmosphere. . Therefore, the leak-type pressure reducing valve 70 that controls the pressure while leaking the gas by the differential pressure from the atmospheric pressure is not directly affected by the atmospheric pressure fluctuation, and the pressure on the inlet side is stabilized.
[0041]
The third container 30 has a smaller volume than the first container 10 and the second container 20. Thus, the responsiveness of the pressure feedback system formed between the first container 10 and the second container 20 via the communication paths 81 and 82 and the third container 30 is not adversely affected.
[0042]
Further, since the first container 10 and the third container 30 and the second container 20 and the third container 30 are respectively connected through communication passages 81 and 82 as throttles, the slight differential pressure generating device 1 is connected to the outside atmosphere. Hardly affected by pressure fluctuations. That is, the external atmosphere causes a pulse-like (rapid) pressure fluctuation due to the opening and closing of the door due to the hermeticity of the building in which the slight differential pressure generating device 1 is installed. In addition, a gradual pressure change due to a change in the weather also occurs. Then, these pressure fluctuations having different properties are absorbed before being transmitted from the small-capacity third container 30 to the large-capacity first container 10 through the communication path 82, and from the same small-volume third container 30. Absorbs complementarily until it reaches the second container 20 having a large volume through the communication passage 81.
[0043]
That is, the third container 30, the second container 20 and the first container 10 having a larger volume than the third container 30, and the communication passages 81 and 82 between the containers cooperate with each other to be affected by the pressure fluctuation of these different properties. Absorb. Further, with respect to the pulse-like pressure fluctuation accompanying the opening and closing of the door of the building, the atmosphere opening pipe 31 also acts as a throttle and absorbs this to some extent in advance.
[0044]
Therefore, the influence of various pressure fluctuations in the atmosphere hardly reaches the third valve (pressure loss generating section) 63, and the pressure drop in the third valve 63 is performed stably, without being affected by the external atmosphere. In addition, it is possible to stably generate a small differential pressure of 1 Pa to 3000 Pa between the upstream side and the downstream side in the third valve 63.
[0045]
After the fine differential pressure adjustment of the fine differential pressure gauge 90 is completed as described above, the second valve is closed.
[0046]
Finally, the following operation is performed as post-processing.
[0047]
First, N ₂ Close the (nitrogen) introduction valve (not shown).
[0048]
Next, after confirming that the pressure on the secondary side of the pressure reducing valve is 0 MPa, the HI pressure side pipe 65 and the LO pressure side pipe 66 of the differential pressure gauge 90 are disconnected.
[0049]
In the above-described embodiment, the first valve 61 is a fixed throttle, the second valve 62 is a variable flow throttle, and the first valve 61 mainly performs a pressure reducing operation and the second valve 62 performs a flow control operation. However, the first valve 61 and the second valve 62 may be combined into one valve to simultaneously perform the pressure reduction and the flow rate control. Further, the first to third valves 61 to 63 are not limited to needle valves. Further, if there is an inexpensive pressure reducing valve having a function of simultaneously performing the pressure reducing action of the first valve 61 and the flow rate controlling action of the second valve 62, the first valve 61 and the second valve 62 are provided with the pressure reducing valve. The function of the valve 62 may be performed.
[0050]
Further, the first container 10, the second container 20, and the third container 30 only need to have airtightness, and may be made of metal or reinforced plastic. Similarly, the pipe 60, the first communication path 81, the second communication path 82, the HI pressure supply pipe 65, and the LO pressure supply pipe 65 may be made of metal or resin.
[0051]
Further, like the slight differential pressure generating device 1 in the above-described embodiment, the third container 30 is not necessarily required, and the first communication path 10 and the second communication path 20 are used as one communication path. An air discharge hole may be provided on the way. Also with this configuration, the gas in the first container 10 and the gas in the second container 20 are exhausted from the common open-to-atmosphere hole provided in a part of the pipe connecting these containers, so that the influence from the atmosphere is obtained. Is not separately received by the first container 10 and the second container 20. That is, for example, in the case of an equivalent electric circuit, a common ground is taken instead of taking separate grounds, and the pressure reduction characteristic of the flow rate is stabilized. However, by providing the third container 30, the influence from the surrounding atmosphere is mainly absorbed by the third container 30, and the effect that cannot be completely absorbed by the first container 10 or the second container 20 becomes a buffer. Therefore, the operation is more stable than when the third container 30 is not provided.
[0052]
In the above-described embodiment, two pressure reducing valves 51 and 52 are arranged in series on the pipe 60 from the tank 50 to the leak-type pressure reducing valve 70. However, the pressure generated in the tank is lower than that in the above embodiment. If they are sufficiently small, these two pressure reducing valves are not always necessary.
[0053]
Furthermore, instead of using a nitrogen tank or a helium tank as a fluid supply source, a compressor that solves the problem of generation of dust and the like may be used.
[0054]
Furthermore, the pipe for opening to the atmosphere does not necessarily have to have an inner diameter smaller than that of the other pipes and communication passages. The same aperture effect as in the above-described embodiment can be achieved. Although the pipe for opening to the atmosphere may be omitted, it is preferable to provide the pipe for opening to the atmosphere in order to minimize the influence of the atmosphere.
[0055]
【The invention's effect】
As described above, the slight differential pressure generating device according to claim 1 of the present invention includes a leak type pressure reducing valve housed in the first container on the inlet side of the pipe, and the outlet side of the pipe. Is connected to the second container and is open to the atmosphere via a communication passage between the second container and the first container. That is, the outlet side of the pipe is not directly opened to the atmosphere, but is opened to the atmosphere via the second container and the connection pipe. In addition, the fluid leaked into the first container in the leak type pressure reducing valve is discharged to the atmosphere via a communication path serving as a throttle. That is, the fluid leaked by the leak-type pressure reducing valve fills the second container, a part of the fluid moves to the first container via the communication path, and the remaining part is discharged to the atmosphere from the atmosphere opening portion of the connection pipe. It is supposed to be. That is, the first container and the second container are filled with the fluid discharged from the leak-type pressure reducing valve and the fluid discharged from the pipe outlet, respectively. The fluid is discharged from. Thereby, the first container and the second container complement each other in the process of filling with the fluid, and the fluid can be more stably discharged to the atmosphere as compared with the case where the fluid is separately discharged to the atmosphere. In addition, when the influence from the atmosphere is received from the leak type pressure reducing valve or the pipe outlet, the influence from the atmosphere is not separately received, and the influence is received through the common atmosphere opening part. And the first vessel, the second vessel, and the connecting line cooperate to substantially absorb different types of influence from the atmosphere.
[0056]
Therefore, the leak-type pressure reducing valve that controls the pressure while leaking the gas by the differential pressure from the atmospheric pressure is not directly affected by the atmospheric pressure fluctuation, and the pressure at the pipe inlet side is stabilized, and the pipe outlet side Pressure also stabilizes. This allows a constant flow rate of fluid to flow through the pipe without being affected by the external atmosphere. Then, a stable pressure loss is generated in the pressure loss generating section due to the viscosity of the gas, and a more stable constant differential pressure can be generated upstream and downstream of the pressure loss generating section.
[0057]
Further, in the fine differential pressure generating device according to the second aspect of the present invention, the pressure in the pipe is sufficiently reduced by the pressure reducing means, and the flow rate is adjusted by the flow rate adjusting means. To be generated.
[0058]
Further, in the slight differential pressure generating device according to the third aspect of the present invention, by providing the third container, the third container mainly absorbs the moderate pressure fluctuation received from the surrounding atmosphere, and the third container also absorbs the moderate pressure fluctuation. The first container or the second container serves as a buffer to absorb the influence that cannot be completely eliminated. In addition, since the connecting conduits between the third container, the first container, and the second container also serve as throttles, abrupt pressure fluctuations received from the surrounding atmosphere are absorbed by these throttles. Therefore, the pressure loss generating section is less likely to be affected by the atmosphere, and a more stable generation of a small differential pressure is possible.
[0059]
Also, in the slight differential pressure generating device according to claim 4 of the present invention, since the volume of the third container is smaller than the volumes of the first container and the second container, the third container is connected to the second container via the connecting pipe and the third container. The response of the pressure feedback system formed between the two containers and the first container is not adversely affected.
[0060]
In addition, since the volumes of the first container and the second container are larger than those of the third container, the third container and the connection conduit connected to the third container out of the gradual pressure fluctuation and the pulsating pressure fluctuation received from the surrounding atmosphere. The pressure fluctuation that cannot be absorbed by the pressure can be reduced.
[0061]
Therefore, the pressure drop in the pressure loss generating section is stably performed, and a slight differential pressure can be stably generated in the pressure loss generating section without being directly affected by the external atmosphere.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a micro differential pressure generating device according to an embodiment of the present invention in a state where a micro differential pressure gauge and a reference pressure gauge are connected.
FIG. 2 is a diagram showing a schematic configuration of a conventional fine differential pressure generating device.
[Explanation of symbols]
1 Slight differential pressure generator
10 First container
20 Second container
30 Third container
31 Air release pipe
50 tanks
51,52 Pressure reducing valve
60 pipes
61 1st valve
62 2nd valve
63 3rd valve
65 HI pressure supply pipe
66 LO pressure supply pipe
70 Leak type pressure reducing valve
81 1st passage
82 Second communication passage
90 differential pressure gauge
91 HI pressure side inlet
92 LO pressure side inlet
95 Reference pressure gauge
100 first slight differential pressure generator
110 sealed container
111, 112 Closed space
121, 122 piping
130 pump
131 cylinder
140 differential pressure gauge
141 HI pressure side inlet
142 LO pressure side inlet

Claims (4)

A fluid supply source capable of supplying a fluid at a predetermined pressure,
A pipe having one end connected to the fluid supply source;
A leak-type pressure reducing valve provided in the middle of the pipe,
A first container in which the leak-type pressure reducing valve and the downstream partial pipe of the pressure-reducing valve are housed, and a fluid is leaked from the leak-type pressure reducing valve to the inside;
A second container connected to the other end of the conduit;
Two branch pipes branch connected to a part of the leak type pressure reducing valve downstream side pipe housed in the first container, and connectable to the HI pressure side and the LO pressure side of the micro differential pressure gauge to be calibrated,
A connection pipe that connects the first container and the second container in communication with each other and has a part that is open to the atmosphere,
A small pressure difference generating device, wherein a pressure loss generating portion is formed between two branch pipes of the pipe. 2. The device according to claim 1, wherein the pressure loss generating unit includes a pressure reducing unit and a flow rate adjusting unit. 3. A third container is interposed in a predetermined portion of a connection pipe connecting the first container and the second container, and an air opening portion is provided in the third container instead of the air opening portion according to claim 1. The device according to claim 1, wherein the device is a differential pressure generating device. 4. The micro container according to claim 3, wherein the first container, the second container, and the third container have a volume of the third container smaller than a volume of the first container and the second container. Differential pressure generator.

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