JPH08219918A - Diaphragm unit of differential pressure detector - Google Patents

Abstract

PURPOSE: To enhance the reliability of protective function by providing a shallow columnar space cut in right angle from the inner circumference at the planar ring part of a flange, and a conical inner space for encapsulating a pressure transmission liquid formed contiguously thereto. CONSTITUTION: A shallow inner columnar space is cut in right angle while leaving a planar ring part at the fringe part of flanges 5, 6. It is then cut into a truncated cone contiguous to the columnar space. Pressure receiving area of a protective diaphragm 4 is determined by subtracting the area of the planar ring part at the fringe part of the flanges 5, 6 from the total area. Since the pressure receiving area of the protective diaphragm 4 is invariant regardless of fluctuation in the welding conditions, an invariant protective pressure can be constantly ensured upon application of an undue shifted pressure thus enhancing the reliability of protective function.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm unit for transmitting each pressure related to a measured differential pressure of a fluid to a differential pressure detecting portion and protecting the differential pressure detecting portion from excessive single pressure.
In particular, the present invention relates to a diaphragm unit of a differential pressure detecting device in which the pressure receiving area of a protective diaphragm is made constant and a constant protective pressure is applied to a differential pressure detecting portion when an excessively large partial pressure is applied to improve the reliability of the protective function.

[0002]

2. Description of the Related Art A conventional diaphragm unit will be described with reference to FIG. 2A and 2B relate to a conventional example, FIG. 2A is a sectional view thereof, and FIG. 2B is a detailed sectional view of an outer peripheral portion thereof. As shown in the drawing, the diaphragm unit 27 has the flanges 7 and 8 arranged so as to sandwich the disc-shaped protective diaphragm 4 from both sides.
The outer peripheral portion is integrally fixed by welding. The surface of each of the flanges 7 and 8 facing the protective diaphragm 4 is a flat conical surface having the surface of the protective diaphragm 4 as the bottom surface, and a pressure-conducting hole (not marked) is connected to the apex of the surface, from which a differential pressure is applied. The respective pressures are transmitted and act on the protective diaphragm 4. At the same time, each pressure is transmitted to the corresponding side of the differential pressure detector, not shown here.

The diaphragm unit 27 is caused by an erroneous operation,
When any one of the pressures acts as an excessive piece pressure, the differential pressure detection unit has a function of applying a constant protective pressure to protect it. This protection function will be described with reference to FIG. 3, which is a cross-sectional view of the differential pressure detecting device in which the diaphragm unit 27 is incorporated. First, the overall configuration will be described, and then the protection function will be described.

In FIG. 3, the differential pressure detecting device 20 mainly comprises a main body 21 having the differential pressure detecting portion 1 and a diaphragm unit 27 built therein, a sub body 25, covers 28 on both left and right sides, and an upper case 30. Become. The main body 21 is in the shape of a cylinder having parallel end faces on both left and right sides, and a bottomed counterbore hole 21a having two counterbored parts is formed from the left end face. The right end surface of the main body 21 has a gap with the seal diaphragm 22 provided here, and a corrugated pattern corresponding to this is processed. The seal diaphragm 22 receives one of the introduction pressures related to the measured differential pressure. Body
The hole 21b that penetrates so as to open to the right end surface of 21 and the first-step small-diameter counterbore surface of counterbore hole 21a is also provided from the second-step large-diameter counterbore surface of counterbore hole 21a. Hole 21c leading to 1
Is opened. In addition, a hole without a reference numeral is formed in the hole 21b from the lower part of the outer peripheral surface of the main body 21, and this hole is for filling the internal space with silicone oil which is a liquid for pressure transmission. It is sealed by 23 and a set screw 24.

The diaphragm unit 27 has a disk shape, and as shown in a partially cutaway view, a disk-shaped protective diaphragm 4 and
It has a conical space which is arranged on both left and right sides thereof and has no reference numeral, and a hole which communicates with this space. The diaphragm unit 27 is inserted in the counterbore part of the first step of the counterbore hole 21a. The differential pressure detecting portion 1 is inserted into the counterbore hole 21a of the main body 21, and the lead portion 2 from the differential pressure detecting portion 1 is pulled out upward from the upper portion of the outer peripheral surface of the main body 21. The sub body 25 has a disk shape and has a hole 25a penetrating in the axial direction. Sub body 25
The left side surface has a gap with the other introduction pressure receiving seal diaphragm 26 related to the measured differential pressure, and the corrugated waveform corresponding to this is processed. Sub body 25 has counterbore hole 21
The hole 25a is inserted into the spot facing portion of the second stage of a and fixed by welding, and the hole 25a communicates with the conical space on the left side of the diaphragm unit 27. After the differential pressure detection unit 1, the diaphragm unit 27 and the sub body 25 are inserted into the main body 21 and fixed by welding, the main body 21
The inner space between the diaphragm unit 27 and the sub body 25 is filled with silicone oil, and after filling, the ball 23 and the set screw 24 are sealed as described above.

The covers 28 on the right and left sides are provided with holes (at right angles to the paper surface for the respective one of the introduction pressures related to the measured differential pressure).
(Not shown) to cover the seal diaphragms 22 and 26 and to hermetically seal the main body 21 through the O-rings 29, respectively.
On the other hand, they are fixed by fastening with screws (not shown). The upper case 30 is a tubular member having an amplifier, an arithmetic circuit, an indicator, etc. built therein, and is fixed to the upper portion of the outer peripheral surface of the main body 21 by welding at the peripheral edge thereof.

One of the introduced pressures related to the measured differential pressure is received by the seal diaphragm 22 through an introduction hole (not shown) of the cover 28 on the right side of the main body 21, and one of them is a diaphragm unit via the filled liquid. In the space on the right side of 27, the differential pressure detector 1
Is transmitted to the corresponding side of. The other introduction pressure is received by the seal diaphragm 26 through the introduction hole of the cover 28 on the left side of the main body 21, and one is inserted into the space on the left side of the diaphragm unit 27 and the other through the filled liquid. It is transmitted to the corresponding side of the detector 1. When only one of the introduced pressures related to the measured differential pressure acts as a large one-sided pressure due to an erroneous operation or the like, the well-known protection function based on the protection diaphragm 4 of the diaphragm unit 27 causes the differential pressure detection unit 1 to be overloaded. It is protected from high pressure and is protected from high pressure. Further, all the welded portions in contact with the filled liquid can be structurally located inside the main body 21 so as not to come into contact with the outside air.

The details of the protection function are as follows. In FIG. 3, a differential pressure flow meter (not shown), for example, each introduced pressure (including static pressure) on both sides of the orifice is received by each seal diaphragm 22 and 26, and each introduced pressure is detected as a differential pressure. The pressure is transmitted to the corresponding pressure guiding space of the part 1. Here, each seal diaphragm 22 and 26 has a very small spring constant (soft), and the differential pressure detection device
The not-shown detection diaphragm 20 has an extremely large (rigid) spring constant, and the protective diaphragms 22 and 26 have spring constants between the above two intermediate values. In the differential pressure detection unit 1, the differential pressure based on each introduced pressure is converted into an electric signal by a well-known capacitance type and is output. The above is the case where the normal pressure introduction operation is performed.

However, if only the right seal diaphragm 22 receives a pressure due to an erroneous operation, if the diaphragm unit 27 is not present, the differential pressure detection unit 1 may be damaged by a large one-sided pressure. The diaphragm unit 27 protects the differential pressure detection unit 1 by the operation described below. Now, assuming that only the right seal diaphragm 22 receives pressure, this pressure is, on the other hand, the protective diaphragm 4 of the diaphragm unit 27.
The seal diaphragm 26 on the left side is inflated via the, and on the other hand, it is transmitted to the pressure guiding space on the right side of the differential pressure detecting unit 1. However, this transmitted pressure is limited to a certain value or less by the contact of the right seal diaphragm 22 with the corrugated surface on the right side of the opposing main body 21, so that there is no possibility that the differential pressure detection unit 1 is destroyed, The protection function has worked.

[0010]

The conventional example has the drawback that the protective pressure varies due to the following variations in welding conditions. This will be described with reference to FIG. 2 (b) which is a detailed cross-sectional view (portion B in FIG. 2 (a)) of the outer peripheral portion of the conventional example described above. The side of each of the flanges 7 and 8 facing the protective diaphragm 4 has a protective diaphragm 4
Is processed into a flat conical surface with the bottom surface as the bottom surface. That is, the angle between the conical surface and the surface of the protective diaphragm 4 is very small. Therefore, when the protective diaphragm 4 and the flanges 7 and 8 are integrally fixed to each other by welding at the outer peripheral portions thereof, due to variations in the welding conditions, the peripheral edge portion of each surface of the protective diaphragm 4 and each of the flanges 7 and 8 on both sides. The contact area with the peripheral portion of 8 inevitably varies. Therefore, for example, assuming that the protective pressure acts on the right side surface of the protective diaphragm 4 from the side of the flange 7, the pressure receiving area has variations, so that the force acting on the protective diaphragm 4 has variations, which in turn causes deformation of the protective diaphragm 4. The degree varies. Therefore, the protective pressure will change. The change in the protection pressure means that the protection function for the differential pressure detector is not constant, and the reliability is reduced accordingly.

The problem to be solved by the present invention is to solve the above problems of the prior art, and to protect the differential pressure detecting section by applying a constant protective pressure when an excessively large partial pressure is applied. It is an object of the present invention to provide a diaphragm unit of a differential pressure measuring device with improved function reliability.

[0012]

SUMMARY OF THE INVENTION According to the present invention, each pressure relating to a measured differential pressure of a fluid is transmitted to a corresponding side of a differential pressure detecting portion, and the differential pressure detecting portion is protected from excessive excessive pressure.
In a diaphragm unit in which a flange for arranging a protective diaphragm and an internal space in which a pressure transmission liquid is sealed on each side is integrally fixed at the outer peripheral portion, the flange is provided at a peripheral portion on the side facing the protective diaphragm. The inner space is composed of a cylindrical space that is shallowly engraved at a right angle from the inner circumference of the annular flat surface of the flange, and a conical space that is connected to the annular space. , Is.

[0013]

According to the present invention, since the internal space is composed of a cylindrical space which is shallowly engraved at a right angle from the inner circumference of the annular flat surface portion of the flange, and a conical space which is connected to the cylindrical space, the method of fixing, for example, welding conditions. The variation does not change the pressure receiving area of the protective diaphragm, and therefore the protective pressure becomes exactly constant when an excessively large partial pressure acts.

[0014]

Embodiments of the diaphragm unit of the differential pressure detecting device according to the present invention will be described below with reference to the drawings.
The differential pressure detecting device incorporated in the embodiment is one in which the diaphragm unit 27 is removed in FIG. FIG. 1 relates to a diaphragm unit 3 as an embodiment, (a) is a sectional view thereof,
(b) is a detailed cross-sectional view of the outer peripheral portion (A portion in FIG. 1 (a)). The embodiment is different from the conventional example in that each flange 5, 6
Of the flat conical surface formed on the side facing the protective diaphragm 4 of FIG. In Figure 1 (b),
A shallow cylindrical engraving is made at a right angle to the surface, leaving an annular flat surface at the peripheral edge of each flange 5, 6, and the inner space is carved into a flat conical shape that is connected to this cylindrical engraving. It is formed. Therefore, the protective diaphragm 4
Has a value obtained by subtracting the area of the annular flat surface portion of the peripheral edge portion of each of the flanges 5 and 6 from the total area, and this value does not change due to variations in welding conditions. As a result, the protection pressure becomes exactly constant when the excessive one-sided pressure acts, and the reliability of the protection function is improved accordingly.

[0015]

According to the present invention, since the internal space is composed of the cylindrical space which is shallowly engraved at a right angle from the inner circumference of the annular flat surface portion and the conical space connected to the cylindrical space, the protective diaphragm and each flange. The pressure-receiving area of the protective diaphragm does not change due to the manner of adhesion with, for example, variations in welding conditions, and the protective pressure becomes exactly constant when an excessive piece pressure acts. Therefore, the reliability of the protection function can be improved.

[Brief description of drawings]

1A and 1B are cross-sectional views of the embodiment according to the present invention, and FIG. 1B is a detailed cross-sectional view of an outer peripheral portion thereof.

2A is a cross-sectional view of a conventional example, and FIG. 2B is a detailed cross-sectional view of an outer peripheral portion thereof.

FIG. 3 is a cross-sectional view of a differential pressure detection device incorporating a conventional example.

[Explanation of symbols]

 1 Differential pressure detector 3 Diaphragm unit 4 Protective diaphragm 5,6 Flange

Claims (1)

[Claims] Claim: What is claimed is: 1. A protective diaphragm and a pressure on each side of the protective diaphragm for transmitting each pressure related to the measured differential pressure of the fluid to the corresponding side of the differential pressure detecting unit and protecting the differential pressure detecting unit from excessive single pressure. In a diaphragm unit in which a flange that disposes an internal space in which a transfer liquid is enclosed is integrally fixed at the outer peripheral portion, the flange contacts the peripheral edge of the protective diaphragm at the peripheral edge on the side facing the protective diaphragm. A differential pressure detection device comprising an annular flat surface portion, wherein the inner space is formed of a cylindrical space shallowly carved at a right angle from the inner circumference of the annular flat surface portion of the flange, and a conical space connected to the cylindrical space. Diaphragm unit.