JP3184126B2 - Flow sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid or gas flow sensor, and more particularly to a flow sensor using a diaphragm.

[0002]

2. Description of the Related Art The present inventor has previously proposed a flow sensor for ultrapure water and a chemical solution used in a semiconductor manufacturing process, for example, as disclosed in Japanese Patent Application Laid-Open No. Hei 6-323883. This flow sensor has a primary diaphragm and a secondary diaphragm opposed to each other at both ends of the shaft,
A flow path communicating along the inner surface of both diaphragms and the outer peripheral surface of the shaft is formed so that fluid pressure is applied to the inner surfaces of both diaphragms, and the shaft outer peripheral flow path is an orifice, and the primary diaphragm is A load cell for detecting a back pressure of a primary diaphragm is disposed on a back surface.

[0003] In the above-mentioned prior example, since there is no movable member (for example, an impeller or a float) for detecting the flow rate in the flow path of the fluid to be measured, there is no danger of generation of fine dust (particles) and ultrapure water or It has the great advantage that it can be used optimally for measuring a chemical solution and that the change in flow rate can be obtained directly as an electrical signal, so that subsequent control is easy. However, in connecting two diaphragms arranged opposite to each other by a shaft, or using an orifice in the outer peripheral flow path of the shaft, there is a complicated manufacturing process, and a very small amount, for example, 100 cc per minute.
There was a complaint that it was not always enough to detect the following changes in flow rate.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above circumstances, and has a novel structure which has a simple structure and a compact design, and can cope with a small flow rate change. It is intended to provide a structure of a flow sensor.

[0005]

That is, the present invention provides:
A main body, a chamber formed inside the main body, an inflow portion of a fluid to be measured having an inlet opening to one side of the chamber, and a fluid to be measured having an outlet opening to the other side of the chamber. An outflow portion, a first diaphragm disposed on the inflow portion side in the chamber to define a primary chamber, and a secondary side disposed on the outflow portion side in the chamber so as to face the first diaphragm. A second diaphragm defining a chamber, a bypass flow path from a bypass inlet opening to the primary chamber to a bypass outlet opening to the secondary chamber, and a difference between before and after the bypass flow path interposed in the bypass flow path. A pressure generating orifice and a pressure of a fluid received between the first diaphragm and the second diaphragm which is disposed in contact with the first diaphragm and the second diaphragm. According to the flow rate sensor comprising a strain gauge for detecting the displacement caused by fluctuations.

In the flow rate sensor according to the present invention, a chamber formed inside the main body has a first diaphragm disposed on the inlet side of the fluid to be measured in the chamber and a first diaphragm disposed on the outlet side of the chamber. The arranged second diaphragm defines a primary chamber and a secondary chamber, respectively. The primary-side chamber and the secondary-side chamber are connected by a bypass flow path having an orifice interposed therebetween, and the fluid to be measured flowing into the primary-side chamber from the inflow portion flows from the bypass flow path to the secondary-side chamber. Flows out of the outflow section.

At this time, since the orifice is interposed in the bypass passage, a differential pressure corresponding to the flow rate is generated before and after the orifice, and the pressure difference generated on the primary side and the secondary side is generated in the primary side chamber. The difference between the load applied to the first diaphragm provided and the load applied to the second diaphragm provided in the secondary chamber results in a unidirectional force. A strain gauge is disposed between the first diaphragm and the second diaphragm so as to be isolated from the fluid to be measured. The strain gauge receives a load (kg / cm ² ) generated from the first and second diaphragms, and determines the magnitude of the load by an electric signal (m
A) and the flow rate (cc / min.) Is measured.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is an overall vertical sectional view of a flow sensor showing one embodiment of the present invention, FIG. 2 is a sectional view of a state where the flow sensor is divided by a line 2-2 in FIG. 1, and FIG. It is a graph which shows a change relationship.

As shown in FIGS. 1 and 2, a flow sensor 10 according to the present invention is used in the embodiment for measuring a very small flow rate of ultrapure water or a chemical solution as described above. , Chamber 20 and inflow portion 21 of the fluid to be measured
And the outflow part 23 of the fluid to be measured and the first diaphragm 31
, The second diaphragm 32, the bypass passage 35, the orifice 40, and the strain gauge 50.

In the embodiment, the main body 11 is formed of a fluororesin such as polytetrafluoroethylene (PTFE resin) which is excellent in corrosion resistance due to its use. However, the main body 11 may be formed of a general plastic or metal. Can also. As shown in the figure, the main body 11 is composed of a half-shaped body member 11A and 11B and a combination of these intermediate members 12, and is integrally tightened and attached by a mounting bolt (not shown). Reference numeral 19 in FIG. 2 is a mounting hole.

The chamber 20 includes body members 11A and 11B constituting the body 11 and an intermediate member 12
As shown in the figure, the primary side chamber 2 is formed by diaphragms 31 and 32 described later.
0A, secondary chamber 20B, and intermediate chamber 20
Partitioned into C.

The chamber 20 has an inlet 21 for the fluid to be measured having an inlet 22 opening on one side (primary chamber 20A) and an outlet 24 opening on the other side (secondary chamber 20B). An outflow portion 23 for the fluid to be measured is formed.

The first diaphragm 31 is provided in the chamber 2
0 and the primary chamber 20A
Is defined. Further, the second diaphragm 32 is provided on the outflow portion 23 side in the chamber 20 so that the first diaphragm 3
1 to define a secondary chamber 20B.

In this embodiment, the first diaphragm 31 and the second diaphragm 32 are formed of a fluorine resin such as polytetrafluoroethylene (PTFE resin) having excellent corrosion resistance. The central portions of the first diaphragm 31 and the second diaphragm 32 are formed to be thick, and it is preferable to arrange the thick curved surface portions 31c and 32c so as to face each other in order to enhance the detection accuracy of the strain gauge 50. . Reference numeral 33 denotes a thin movable portion, and reference numeral 34 denotes an outer peripheral portion fixed by the holding block 12.

As shown in the figure, the bypass passage 35 is a passage extending from a bypass inlet 36 opening to the primary chamber 20A to a bypass outlet 37 opening to the secondary chamber 20B. An orifice (portion) 40 is interposed. The orifice 40 may be replaceably disposed as a single member as shown in the figure, but may be formed integrally with the body main body 11 (11A, 11B, 12) if necessary. The orifice 40 has a hole 41 of a predetermined diameter.
And a pressure difference is generated before and after the bypass passage 35 by being interposed in the bypass passage 35.

The strain gauge 50 is a so-called load cell, and is disposed between the first diaphragm 31 and the second diaphragm 32. As shown
The intermediate chamber 20C defined between the first diaphragm 31 and the second diaphragm 32 is a space that does not come into contact with the fluid to be measured, and the strain gauge 50 is at a position where it does not interfere with the bypass flow path 35 as shown in FIG. It is fixed to the body 11.

The strain gauge 50, which is disposed between the first diaphragm 31 and the second diaphragm 32, makes the pressure difference between the fluid generated by the orifice 40 and the first diaphragm 31 equal to that of the first diaphragm 31, as described above. The change in the load difference ΔP (kg / cm ² ) applied to the second diaphragm 32 is detected, and the change in the magnitude of the load difference is converted into an electric signal I (mA) to measure the flow rate (cc / min.). Is what you do.

FIG. 3 is a graph showing an example of a change relationship between the load and the current accompanying the change in the flow rate of the fluid. Here, the orifice 4
0 is set to 0.5 mm, and the flow rate of the fluid is 30 to 90 cc / min. Difference ΔP between the first diaphragm 31 and the second diaphragm 32 corresponding to
Is 0.12 to 0.93 kg / cm ² , and the voltage I during this period is
Varies from 12 to 20 mA. With such a graph, the change in the flow rate is detected as an electric signal by the strain gauge 50 that detects the load difference between the first diaphragm 31 and the second diaphragm 32.

In FIG. 2, reference numeral 51 denotes a strain gauge 50.
Are connected to a display device such as a voltmeter, an arithmetic processing device such as a computer, or various control devices.
The strain gauge 50 can be used in a wide temperature range by attaching a temperature correction gauge. Reference numeral 52 denotes a mounting portion of the strain gauge 50.

[0020]

As described above, according to the flow sensor of the present invention, the primary and secondary diaphragms define the primary chamber and the secondary chamber, and the primary chamber and the secondary chamber are separated from each other. Since the side chamber is connected by a bypass flow path and an orifice is interposed in the bypass flow path, the differential pressure generating mechanism for detecting the flow rate has a simple structure and a compact design. This has great advantages in production, use, and the like.

In particular, an orifice (part) is provided in the bypass passage.
, The diameter of the orifice can be set arbitrarily, and the diameter can be made extremely small for detecting a very small amount of flow as in the embodiment. When the orifice is an independent member, it can be replaced according to the diameter of the orifice.

In addition, according to the structure of the present invention, since the pressure difference is detected by the diaphragm, there are few failures, there is no possibility of generation of fine dust (particles), and a chemical solution which dislikes impurities, ultrapure water, etc. Ideal for measuring In addition, since the change in the differential pressure of the diaphragm due to the change in the flow rate is directly detected by the strain gauge, the response is extremely fast.
As described above, the flow sensor of the present invention is extremely useful as a flow sensor for a chemical solution, ultrapure water, or the like.

[Brief description of the drawings]

FIG. 1 is an overall vertical sectional view of a flow sensor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view in a state of being cut in half by a line 2-2 in FIG.

FIG. 3 is a graph showing a change relationship between a load and a current according to a flow rate change.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Flow rate sensor 11 Main body 20 Chamber 20A Primary chamber 20B Secondary chamber 21 Inflow part 23 Outflow part 31 First diaphragm 32 Second diaphragm 35 Bypass flow path 40 Orifice 50 Strain gauge

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01F 1/38 G01F 1/42

Claims (1)

(57) [Claims] 1. A main body, a chamber formed inside the main body, an inflow portion of a fluid to be measured having an inlet opening on one side of the chamber, and an outlet opening on the other side of the chamber. A first diaphragm disposed on the inflow side of the chamber to define a primary chamber; and disposed on the outflow side of the chamber in opposition to the first diaphragm. A second diaphragm defining a secondary chamber, a bypass flow path extending from a bypass inlet opening to the primary chamber to a bypass outlet opening to the secondary chamber, And an orifice for generating a differential pressure before and after the first diaphragm and the second diaphragm, the orifice being disposed in contact between the first diaphragm and the second diaphragm. Flow sensor characterized by comprising a strain gauge for detecting the displacement caused by pressure fluctuations of the fluid is subjected.