JP2805516B2 - Measuring method and measuring device for micro flow gas - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and apparatus for measuring a gas having a small flow rate.

(Prior art) In semiconductor manufacturing equipment and vacuum equipment, the flow rate is 0.
It is often necessary to detect a gas with a small flow rate of about 01 to 0.02 cc / min or measure the flow rate.

The inventor of the present invention has previously developed a membrane flow meter as shown in FIG. 3 as a measuring device for a minute flow gas as described above, and has disclosed it (Japanese Patent Application Laid-Open No. 63-222221).

That is, the ring 2 dipped in the soap solution 1 is
Is lifted upward through the ring, so that a soap liquid film 1a is formed inside the ring body 2 and this is attached to the lower end face 4a of the detection tube 4.
The lower end opening 4b is closed by contact and adhesion.

The soap liquid film 1a closing the lower end opening 4b of the detection tube 4 is
The gas to be measured 5 is moved upward in the detection tube 4 at a predetermined speed. Now the soap film 1a passes through the point P ₁ and point P _2, the passage is detected by the liquid film detection sensors 6a and liquid film detecting sensor 6b, at the computer 7, the two points P ₁ · P ₂ The flow rate of the gas to be measured 5 is calculated based on the passing time between the two.

However, in the membrane flow meter disclosed in JP-A-63-222221, the rising speed of the soap liquid roll 1a greatly varies depending on the degree of decoating of the inner wall surface 4c of the detection tube 4, and the flow rate of the gas 5 to be measured is small. When the rising speed of the liquid film 1a is low, there is a disadvantage that the measurement accuracy is significantly deteriorated.

Further, in order to smoothly raise the liquid film 1a, the inner wall surface 4c of the detection tube 4 is wetted with the soap liquid 1 in advance, but the soap liquid for wetting hangs down with the passage of time. As a result, it is relatively hot and adheres to the lower end surface 4a of the detection tube 4. Then, when the liquid film 1a formed inside the ring body 2 adheres to the lower end surface 4a of the detection tube 4, the lower end opening 4b is closed by the accumulation of the wetting soap liquid on the lower end surface 4a. As a result, the thickness of the soap liquid film 1a fluctuates, and as a result, there is a problem that the rising speed of the liquid film 1a changes and measurement errors occur.

Further, the soap liquid film 1a once formed inside the ring body 2 is attached to the lower end surface 4a of the detection tube 4, and the lower end opening 4b is closed by the soap liquid film 1a.
Is difficult to stably adhere to the lower end surface 4a of the detection tube 4, and there is a problem that the liquid film 1a often breaks.

(Problems to be Solved by the Invention) The present invention relates to the above-described problems in the conventional membrane flow meter,
That is, (a) when the gas flow rate is very small, the rising speed of the liquid film greatly varies due to the wetting condition of the inner wall surface of the detection tube and the accumulation state of the soap solution at the lower end surface of the detection tube, and the measurement accuracy is significantly deteriorated. (B) It is difficult to always close the lower end opening of the detection tube accurately by the soap liquid film, and the liquid film is often damaged, and the problem of troublesome flow detection is solved. Fine flow rate that enables simple and high-precision flow measurement even with a small fluid flow rate, and enables easy and reliable formation and adhesion of the necessary soap liquid film, greatly improving measurement accuracy and measurement efficiency. A method and an apparatus for measuring gas are provided.

(Means for Solving the Problems) The present invention relates to a main body case 7 in which a soap solution 1 is stored; and an upper end opening 4d in the main body case 7 projecting upward from a liquid level L of the soap solution 1. A detection tube 4 opened at least; a soap liquid film deposition device 8 for closing an upper end opening 4d of the detection tube 4 with a soap liquid film 1a; and the soap liquid film 1a expanded by a gas 5 to be measured. soap liquid film detection device 9 for detecting the arrival of the fixed position of; the atmosphere communication valve V ₂ tens purge valve V ₃ for supplying a purge gas into the detector tube 4 which communicates with the atmosphere above the detector tube 4 Ventilation control device to control each
10; a soap liquid film 1a for closing the tip opening 4d of the detection tube 4
The CPU device 11 that measures the time from the start of expansion of the sample to the detection of the soap liquid film 1a by the soap liquid film detecting device 9 and calculates the gas flow rate from the measured time is a base configuration of the present invention.

Further, the present method invention, pull the detector tube 4 by opening the atmosphere communication valve V ₂ after communicating to the atmosphere, the ring body 2 soaked into the soap solution 1 in a state that allowed insertion of the detector tube 4 upward ,
Closing the upper end opening 4d of the detector tube 4 by soapy water film 1a Azusa, the inflating soap liquid film 1a which closes the upper end opening 4d by a subsequent said atmosphere communication valve V ₂ gas to be measured 5 by closing, the soap The expansion start time of the liquid film 1a is measured, and the arrival of the soap liquid film 1a at a certain position is detected by reflecting the optical signal H by the expanded soap liquid film 1a, and the expansion of the soap liquid film 1a is performed. The basic configuration of the present invention is to measure the time from the start to the detection of the arrival of the soap liquid film 1a at a certain position, and to calculate the flow rate of the measured gas 5 from the measured time.

By releasing the (working) atmosphere communication valve V _2, the detector tube 4 is in a state of being communicated with the atmosphere.

In this state, when the ring body 2 is pulled up from the soap solution 1 with the detection tube 4 inserted therethrough, first, a soap liquid film 1a is formed between the outer wall surface of the detection tube 4 and the ring body 2, and then, When the ring body 2 reaches the position of the upper end opening 4d of the detection interval 4, the opening
4d is closed by the liquid film 1a.

After that, when closing the atmosphere communication valve V _2, the detector tube 4 by the gas 5 is pressurized, soapy water film 1a is expanded.

When the upper portion of the expanded soap liquid film 1a reaches a certain position, the optical signal S is reflected by the liquid film 1a, and the light incident on the light receiving portion 9b is blocked. Thereby, the arrival of the liquid film 1a at a certain position is detected.

Also, by measuring the time from the start of the expansion of the liquid film 1a to the detection, from the time, to determine the gas flow rate using a previously measured time-flow rate characteristic, or
The gas flow rate is obtained from the measured time and the calculated value of the internal volume of the expanded liquid film.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is an overall configuration diagram showing a cross section of a part of a measuring device for measuring a small amount of gas according to the present invention. In FIG. 1, parts common to FIG. 3 are denoted by the same reference numerals. I have. .

The apparatus for measuring a small amount of gas according to the present invention includes a main body case 7 in which a soap solution 1 is stored, a detection tube 4 having an upper end opening protruding upward from a liquid level L of the soap solution 1, and a detection tube 4. A soap liquid film attaching device 8 for closing the upper end opening 4d with the liquid film 1a of the soap liquid 1, a soap liquid film detecting device 9 for detecting that the soap liquid film 1a has reached a predetermined position, and an atmosphere communication valve V ₂ a venting control device 10 and through a purge valve V ₃ to control the ventilation of the inner detector tube 4, CPU 11 or the like for calculating the flow rate of the gas to be measured 5 by the signal S or the like from the liquid soap film detector 9 Is formed from.

The main body case 7 is a box body having a reservoir 7a for the soap liquid 1 formed therein, and is provided with an air vent 7b, a soap supply port 7c, and the like. An insertion hole 7d for the detection tube 4 is formed in the center of the bottom of the main body case 7, and the detection tube 4 is inserted into the insertion hole 7d from below, and the upper end opening 4d is located above the soap liquid level L. It is fixed in an airtight manner so that the vertical position can be adjusted in a state where it protrudes. In FIG. 1, reference numeral 12 denotes a nut for fixing the detection tube, and reference numeral 13 denotes an O-ring.

An inlet 14 for the gas 5 to be measured, a communication port 15 to the atmosphere, and a supply port 16 for the gas 17 for purging are provided on the side wall of the detection tube 4, respectively. 5 of the supply hole 7e, air communication hole 7f, through the supply holes 7g of the purge gas 16, respectively subjected試弁V _1, the air communication valve V _2, is communicated to the purge valve V _3.

The soap liquid film deposition device 8 includes a ring body 2 that moves up and down with the upper end of the detection tube 4 inserted, a cylinder device 3 that drives the ring body 2 in the vertical direction, and an operation of the cylinder device 3. Cylinder control valve V ₄ for controlling supply of working fluid
And so on.

The cylinder 3 is actuated to pull up the ring body 2 which has fallen into the soap solution 1 so that the detection tube 4
A liquid soap film 1a is formed between the outer wall surface and the ring body 2, and the liquid film 1a adheres to the upper end opening 4d of the detection pipe 4 at the moment when the ring body 2 is pulled up from the upper end of the detection pipe 4. Then, the upper end opening 4d is opened by the soap liquid film 1a.

The soap liquid film detecting device 9 is an optical fiber type light emitting section.
9a, a light receiving section 9b, a fiber amplifier 9c, and the like. That is, the optical signal H output from the amplifier 9c is
Optical fiber 9d-radiation part 9a-light receiving part 9b-optical fiber 9e
To the amplifier 9c, the soap liquid film 1a at the tip opening 4d of the detection tube 4 expands, enters into the optical path of the optical signal H, and the optical signal H is totally reflected by the liquid film 1a. Thus, the arrival of the soap liquid film 1a at a predetermined position is detected.

Said vent control apparatus 10 provided試弁V ₁ and atmosphere communication valve V ₂ of the gas 5 to be measured, the purge valve V _3, is for controlling the opening and closing of such cylinder control valve V _4, each in the order such as described below valve
Close control of V ₁ ~V ₄ is performed.

Said CPU unit, the atmosphere communication valve V ₂ after the closed as will be described later, based on the time until the liquid soap film 1a inflated with gas to be measured 5 is detected by the soap-film detection device 9, the gas 5 is used to calculate the minute flow rate, and it goes without saying that a microcomputer or the like may be used.

Next, a method of measuring a small flow rate gas using the small flow rate measurement device of FIG. 1 will be described.

First, the soap solution 1 is introduced into the soap solution storage section 7a in the main body case 7.
While maintaining the liquid level L at a predetermined position,
The distance G between the upper end of the detecting tube 4 and the center H 'of the optical signal path of the soap liquid film detecting device 9 is adjusted to a predetermined value.

The distance G is appropriately selected according to the flow rate level of the gas 5 to be measured.
Is also selected to be larger.

Next, the ring device 2 is moved up and down by operating the cylinder device 3 to wet the outer wall surface and the upper end surface of the detection tube 4 with the soap liquid film 1a.

In the measurement, as shown in the time chart of FIG. 2, first, a purge valve V ₃ closed, the atmosphere communication valve V ₂ opened, subjected試弁V ₁
It was in the open state, the ratio measurement gas 5 introduced into the detector tube 4 through subjected試弁V _1, to a state of release through the atmosphere communicating valve V ₂ to the atmosphere.

Next, the ring device 2 dipped in the soap solution 1 is pulled upward by operating the cylinder device. As a result, the liquid film 1a formed between the ring body 2 and the detection tube 4 is
4d, the tip opening 4d of the detection tube 4 is closed by the soap liquid film 1a. At this time, although the gas 5 is supplied to the detector tube 4 through subjected試弁V _1, since the atmosphere communication valve V ₂ is opened, soapy water film for closing the tip opening 4d of the detector tube 4 1a is kept almost flat.
If the case of not providing the atmosphere communication valve V ₂ is subjected試弁V ₁
Is closed, the soap liquid film remains on the upper opening 4d of the detection tube 4.
1a, the liquid film 1a is formed by the expansion of the gas in the ventilation pipe 4.
Starts to expand, making accurate flow measurement difficult.

When soap solution film 1a by the tip opening 4d of the detector tube 4 is closed, the atmosphere communication valve V ₂ is closed, it starts counting with the timer or CPU unit 11 at the same time this.

When closing the atmosphere communication valve V _2, the soap liquid film 1a starts to expand due to be measured gas 5. When the soap liquid film 1a expands and the upper portion of the film surface reaches the vicinity of the optical path center H 'of the soap liquid film detecting device 9, the optical signal H incident from the radiating portion 9a to the light receiving portion 9b is changed to the liquid film. The light is totally reflected by 1a, and the light entering the light receiving section 9b is blocked. Accordingly, the detection signal S from the fiber amplifier 9c is sent to the CPU unit 11, the time counter that is started simultaneously with the closing of the atmosphere communication valve V ₂ is stopped.

Wherein the CPU unit is subsequently using said time measurement values to the total reflection of the atmosphere communication valve optical signal with soap liquid film 1a from closure of the V ₂ H, gas flow rate is calculated, on the display (not shown) While being displayed, operations such as recording are performed appropriately.

Note that the relationship between the measured value of the time and the gas flow rate can be measured in advance, and when the distance G between the tip of the detection tube 4 and the optical path center H ′ is constant, the liquid film 1a reaches A substantially inversely proportional relationship is established between the time required to reach this and the gas flow rate value.

In the present embodiment, the gas flow rate is determined from the relationship between the measurement time and the flow rate determined in advance, but the internal volume of the expanded liquid film 1a is determined from the height of the expanded liquid film by the CPU device. Alternatively, the flow rate of the gas 5 may be calculated from the calculated value of the internal volume and the measured time.

When the soap liquid film detecting device 9 is actuated, released by the purge valve V ₃ is a slight time after a predetermined time has elapsed, soap liquid adhering to the inner wall surface of the tip opening 4d of the detector tube 4 is removed.

When the purging operation is not performed, the soap liquid dropped due to the breakage of the liquid film causes the upper end opening 4d of the detection tube 4 to be opened.
Of the soap liquid film 1a formed in the opening 4d by the ring body 2 or the liquid film 1a is formed again by the attached soap liquid. This causes measurement errors and measurement troubles.

By operating the purge valve V ₃ is completed, the cylinder control valve
Ring body 2 by V ₄ is lowered into the soap solution 1, further completes the measurement of the gas flow once been released atmosphere communication valve V _2.

The flow rate of the gas 5 is measured by repeating the above-described weighing operation at predetermined time intervals.

(Effect of the Invention) In the present invention, the soap liquid film 1a formed at the tip opening 4d of the detection tube 4 is expanded toward the atmosphere,
The optical signal H is totally reflected by the expanded soap liquid film 1a, thereby detecting that the soap liquid film 1a has reached a predetermined position. As a result, the soap liquid film 1a is always expanded under constant external conditions without being affected by the state of the inner wall surface of the detection tube 4 at all unlike the conventional membrane flow meter, and the soap liquid film 1a The arrival at a certain position is detected very accurately, and the measurement accuracy of the fine particle amount is greatly improved.

Further, the ring body 2 immersed in the soap solution 1 is pulled upward by an upper body having the detection tube 4 inserted therein, so that the upper end opening 4d of the detection tube 4 is closed by the liquid film 1a. Therefore, the upper end opening 4d of the detection tube 4 can be very reliably closed by the liquid film, and there is no trouble such as breakage of the liquid film as in the case of the conventional membrane flow meter.

Furthermore, since the as the inside of the detector tube 4 which closes communicated to atmosphere, completely prevents the expansion of the in soapy water film 1a before the start of measurement by a liquid film 1a through the atmosphere communication valve V _2,
As the accuracy of measuring the amount of fine particles increases, the measurement itself can be performed smoothly and efficiently.

As described above, the present invention has excellent practical effects.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram in which a part of a minute flow rate measuring device according to the present invention is longitudinally cut. FIG. 2 is an explanatory view showing the operating state of each device in measuring the amount of fine particles using the apparatus of the present invention. FIG. 3 is an explanatory view of a conventional membrane flow meter. DESCRIPTION OF SYMBOLS 1 ... Soap liquid 1a ... Soap liquid film 2 ... Ring body 3 ... Cylinder device 4 ... Detection tube 4d ... Top opening 5 ... Gas to be measured 7 ... Main body case 8 ... Soap liquid film adhesion 9 ...... soap solution film detecting device 10 ...... venting control device 11 ...... CPU device H ...... optical signal H '...... optical signal path center G ...... distance V ₁ ...... subjected試弁V ₂ ...... atmosphere Communication valve V ₃ …… Purge valve V ₄ …… Cylinder control valve

Continuation of front page (72) Inventor Naofumi Yasumoto 30 Aramotokita, Higashiosaka-shi, Osaka Harumiya Housing No. 187-796 (56) References Japanese Patent Publication No. Sho 40-15757 (JP, B1) (58) Fields investigated ( Int.Cl. ⁶ , DB name) G01F 1/708

Claims (5)

(57) [Claims] 1. A main body case (7) containing a soap liquid (1) therein; and an upper end opening (4d) in the main body case (7) above a liquid level (L) of the soap liquid (1). A detection tube (4) disposed so as to protrude from the upper end of the detection tube (4);
a soap liquid film deposition device (8) in which d) is closed by a soap liquid film (1a); and detection of arrival of the soap liquid film (1a) expanded by the gas to be measured (5) to a certain position. soapy water film detection device (9) which, with said sensing tube (4) in a purge valve V ₃ for supplying purge gas to the atmosphere and the atmosphere communication valve V ₂ that communicates to the detector tube (4) in each A ventilation control device (10) for controlling; and a soap liquid film (1a) by the soap liquid film detection device (9) from the start of expansion of the soap liquid film (1a) for closing the tip opening (4d) of the detection tube (4). A small flow gas measuring device, comprising: a CPU device (11) for measuring a time until detection of a gas and calculating a gas flow rate from the measured time. 2. A device for attaching a soap liquid film (8) to a detecting tube (4).
And a cylinder device (2) for vertically moving the ring body (2) and moving the ring body (2) between the soap solution (1) and the upper part of the detection tube (4). 3. The method for measuring a gas with a small flow rate according to claim 1, wherein the method is formed by: 3. A radiating section (9a) and a light receiving section (9b) for an optical signal (S), which are disposed opposite to each other with a soap liquid film detecting device (9);
The micro flow gas measuring device according to claim 1, wherein the gas measuring device is formed by an optical fiber amplifier (9c). 4. The detection pipe (4) by opening the air communication valve (V ₂ ).
After communicating the inside to the atmosphere, the ring body (2) dipped in the soap solution (1) is pulled up with the detection tube (4) inserted, and the upper end opening (4d) of the detection tube (4) is closed. Soap liquid film (1a)
Then, the air communication valve (V ₂ ) is closed, and the soap liquid film (1a) that closes the upper end opening (4d) is expanded by the gas to be measured (5), and the soap liquid film (1a) is closed. ) Is measured, and the expanded soap liquid film (1a) reflects an optical signal (H) to detect the arrival of the soap liquid film (1a) at a certain position,
Measuring the time from the start of expansion of the soap liquid film (1a) to the detection of the arrival of the soap liquid film (1a) at a certain position, and calculating the flow rate of the gas to be measured (5) from the measured time. Characteristic method of measuring small flow gas. 5. An inner volume of the expanded liquid film (1a) is calculated from a distance (G) between a tip opening (4d) of the detection tube (4) and a detection point of the expanded soap liquid film (1a). The method according to claim 4, wherein the flow rate of the gas to be measured (5) is obtained from the calculated value and the measurement time.