JPH08219919A - Differential pressure detector - Google Patents

Abstract

PURPOSE: To stabilize the differential pressure signal by a structure wherein the protective part is not subjected to the influence of compressive force of a cover tightening bolt from each part for receiving the differential pressure to be measured. CONSTITUTION: Seal diaphragms 2, 3 are bonded respectively to the left and right end faces of a main body 1 and a cover 39 is tightened through an O-ring 38 by means of a bolt 40 and a nut 41. Pressure introduction tubes 7, 8 are stood on the outer circumferential face of the body 1 and a unit comprising a protective part, i.e., a protective diaphragm 6, and side boards 4, 5 for defining conical spaces 4a, 5a on the opposite sides thereof is interposed between the pressure introduction tubes 7, 8. The protective diaphragm 6 is located on the outside of the bolt 40 while spaced apart therefrom. With such structure, variation in the tightening force of the bolt 40 due to variation in the ambient temperature has no effect on the gap at the joint of the protective diaphragm 6 and each side board 4, 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a structure in which the protective portion is not affected by the compressive force of the cover fastening bolt of the pressure receiving portion for receiving each pressure of the differential pressure to be measured, and the differential pressure signal is stabilized. The present invention relates to a differential pressure detection device with an overpressure protection function.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view of a conventional example.
Will be described with reference to. In FIG. 3, the conventional example is roughly divided into a detection unit 20 and a protection unit 30, which are pressure guiding tubes.
36 and 37 are connected. The detection unit 20 converts the differential pressure to be measured by the capacitance method into an electric signal and outputs the electric signal.
As will be described later in detail, the detection unit 20 is protected against the introduced pressure. Since the structure of the detection unit 20 is well known, the description thereof will be omitted.

Now, the protection section 30 is mainly composed of the main bodies 31, 32.
, Protective diaphragm 33, sealing diaphragms 34, 3
5, O-ring 38 and process cover with pressure introducing hole
It consists of 39 (hereinafter referred to as cover). Where each body 31,
The members having the same name of 32 and the respective sealing diaphragms 34, 35 are the same, and the O-ring 38 and the cover 39 are each two. The main bodies 31 and 32 are respectively arranged on the left and right sides of the protective diaphragm 33, and are joined to each other at their outer circumferences or peripheral portions.

Also, the same spaces 42, 44 and holes 43, 45 are formed in the main bodies 31, 32, respectively. More specifically, the main body 31 on the right side is described as follows. The space 42 is formed on the left side surface of the main body 31 in the shape of a mortar that is coaxial therewith, and the hole 43 penetrates the main body 31 along its axis and branches from the vicinity of the center of the space 42 to the central hole 46 of the pressure guiding tube 36. It communicates with and communicates with a pressure guiding space (not shown) of the detection unit 20. A cross section of the right side surface of the main body 31 is formed in a corrugated shape, and a seal diaphragm 34 having substantially the same shape as the corrugated shape is fixed to the right side surface of the main body 31 with a space therebetween at its peripheral edge. A cover 39 is attached to the right side of the main body 31 to the outer peripheral edge of the seal diaphragm 34 via an O-ring 38.
The above is substantially the same for the left main body 32. The space that is in contact with the seal diaphragms 34 and 35, the holes 43 and 45, the spaces 42 and 44, and the spaces 46 and 47 is filled with silicone oil (filled liquid) as a pressure transmitting fluid. To be done.

The operation of this conventional example is as follows. When a differential pressure flow meter, for example, each introduction pressure (including static pressure) on both sides of the orifice is received by each seal diaphragm 34, 35, each introduction pressure is applied to the space and the hole 43 in contact with the seal diaphragm 34. , The space 42 and the hole 46 to the pressure-inducing space of one side of the detection unit 20, and the seal diaphragm 45.
Is transmitted to the other pressure guiding space of the detection unit 20 through the space in contact with the hole, the hole 45, the space 44, and the hole 47. The seal diaphragms 34 and 35 have extremely small spring constants (soft), the detection diaphragm (not shown) of the detection unit 20 has extremely large spring constant (rigid), and the protective diaphragm 33 has the spring constant. Takes an intermediate value between the above two. In the detection unit 20,
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 seal diaphragm 34 on the right side receives the pressure due to an erroneous operation, if the protection section 30 is not provided, the detection section 20 may receive a large one-sided pressure and the sensor may be destroyed. Even if only one of the pressures is received by the seal diaphragm due to an erroneous operation in introducing each pressure on both sides of the orifice, the protection unit 30 protects the detection unit 20 by the following operation. Now, assuming that only the seal diaphragm 34 receives pressure, this pressure is
On the other hand, the sealing diaphragm 35 is inflated by being transmitted from the hole 43 and the space 42 through the enclosed liquid and the space 44 and the hole 45 on the left side through the protective diaphragm 3. On the other hand, the hole 45
Is transmitted to the pressure guiding space on the right side of the detection unit 20 via. However, this transmission pressure is limited to a certain value or less by the contact of the sealing diaphragm 34 with the corrugated surface on the right side of the opposing main body 31, so that there is no risk of the sensor being destroyed and the protection function has been activated. Become.

By the way, the differential pressure detecting unit 20 of the conventional example detects the differential pressure based on the electrostatic capacitance formed between the measurement diaphragm and the silicon plate electrodes on each side, which is not shown. It Now, one introduction pressure is P1, the other introduction pressure is P2 (greater than P1), and the corresponding one capacitance value is C1,
If the other capacitance value is C2,

[0008]

## EQU1 ## C1 = .epsilon.A / (d-.DELTA.d) C2 = .epsilon.A / (d + .DELTA.d) where .epsilon .: dielectric constant of filled liquid, A: effective area of electrode,
d is the average gap amount between the measurement diaphragm and the electrode when pressure is not introduced, and Δd is the displacement amount of the measurement diaphragm when pressure is introduced. It is possible to know the differential pressure by obtaining an F value approximately expressed by the following equation through a well-known electronic circuit.

[0009]

[Formula 2] F = (C1−C2) / (C1 + C2) ≈Δd / d = k (P2−P1) Here, the protective diaphragm 33 and each of the main bodies 31 and 32 are Tig welded at the outer periphery of the joint. Alternatively, they are integrally fixed by plasma welding, and each of the square plate-like covers 39 is clamped and clamped from both sides by four sets of bolts 40 (with nuts 41) penetrating the respective four corners. .

[0010]

In the conventional example, since the protective diaphragm 33, the main bodies 31 and 32, and the bolt 40 have different thermal expansion coefficients due to the respective materials, the bolt 40 changes due to a change in ambient temperature. Changes the tightening force of
As a result, the clearance at the contact portion between the protective diaphragm 33 and the main body 31, 32 changes. The schematic cross-sectional view of the main part of FIG. 4 shows the problems of the conventional example. Now, the change in the gap at the contact portion of the joint between the protective diaphragm 33 and each of the main bodies 31 and 32 causes the protective diaphragm 33 to be displaced, in other words, the internal pressures to be changed apparently, resulting in a zero-point fluctuation, which in turn causes a difference. There is a problem of making the pressure signal unstable. Here, since the protective diaphragm 33 is a member that is repeatedly subjected to pressure, stainless steel having spring properties, stainless steel having corrosion resistance and weldability for each body 31, 32, and the bolt 40 having Cr mainly for strength are used. -Mo steel is used respectively. Each coefficient of thermal expansion has a protective diaphragm 33
16.9, body 31, 32 16.0, bolt 40 11.0-12.
0 (both are units: × 10 ^-6 / ° C).

The problem to be solved by the present invention is to solve the above problems of the prior art, and to solve the influence of the tightening force of the cover fastening bolt of the pressure receiving portion for receiving each pressure of the differential pressure to be measured. It is an object of the present invention to provide a differential pressure detection device having an overpressure protection function that stabilizes a differential pressure signal by using a structure that does not receive the protective portion.

[0012]

SUMMARY OF THE INVENTION According to the present invention, a seal diaphragm for receiving each pressure of a differential pressure to be measured is fixed to each end face on both sides of the main body with a gap at the center thereof and fixed at the peripheral portion. , A pressure-receiving portion in which a cover is integrally and hermetically fastened to the main body by bolts at the peripheral portion so as to cover each seal diaphragm; and a protective cauldron-shaped space is formed on each side of the protective diaphragm in opposition thereto. Each of the pressures received by the seal diaphragm is communicated with the corresponding space of the protection unit through the inside of the main body of the pressure receiving unit via the sealed fluid, and In the differential pressure detecting device with the overpressure protection function that transmits to the corresponding side, the protection portion is located away from the fastening bolt of the pressure receiving portion.

Further, the protective portion and the differential pressure detecting portion are arranged outside the pressure receiving portion, or the protective portion is embedded in the pressure receiving portion so as to be located inward from the fastening bolt of the pressure receiving portion. Therefore, it is preferable that the differential pressure detecting portion is arranged outside the pressure receiving portion.

[0014]

According to the present invention, since the protective portion is located away from the fastening bolt of the pressure receiving portion, the protective portion and the differential pressure detecting portion may be arranged outside the pressure receiving portion. , Or the protection part is embedded in the pressure receiving part so as to be located inward from the fastening bolt of the pressure receiving part, and the differential pressure detecting part is
Since it is arranged outside the pressure receiving portion, even if the tightening force of the bolt changes due to the change of the ambient temperature, the influence does not reach the joint between the protective diaphragm and each of the main bodies on both sides. Therefore, the gap at the contact portion at the joint is not changed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the differential pressure detecting device according to the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of the first embodiment. In the figure, the seal diaphragms 2 and 3 are fixed to the left and right end surfaces of the main body 1, respectively.
A cover 39 is fastened with a bolt 40 and a nut 41 via an O-ring 38 to form a pressure receiving portion. The pressure guiding tubes 7 and 8 are erected on the outer peripheral surface of the main body 1, and the detection unit 20 is connected to the tip end side thereof. In the middle of each pressure guiding tube 7, 8, a protection part is formed by connecting them, that is, a protection diaphragm 6, and each side plate 4, forming a mortar-shaped space 4a, 5a arranged on both sides with the protection diaphragm 6 sandwiched therebetween.
A unit consisting of 5 and 5 is provided. The spaces 4a and 5a on both sides of the protective diaphragm 6 communicate with the holes 7a and 8a of the pressure guiding tubes. The L-shaped holes 2a and 3a formed in the body 1 are
One of the openings opens on each end surface of the body 1, and the other communicates with the holes 7a, 8a of the pressure guiding tubes.

The pressure received by the seal diaphragms 2, 3 is transmitted from the holes 2a, 3a of the main body 1 through the holes 7a, 8a of the pressure guiding pipes to the corresponding side of the detecting portion 20 and at the same time. The respective pressures are transmitted to the spaces 4a and 5a on both sides of the protective diaphragm 6, and the protective function against the excessive pressure works as described in the conventional example. Moreover, the protective portion consisting of the protective diaphragm 6 and the spaces 4a, 5a on both sides thereof (that is, the side plates 4, 5) is located outside the position of the bolts 40 for fastening the covers 39 on both sides of the main body 1, in other words, If you are away from bolt 40. Therefore, the change in the tightening force of the bolt 40 due to the change in the ambient temperature does not affect the gap between the contact portions at the joints between the protective diaphragm 6 and the side plates 4 and 5. As a result, the differential pressure signal does not fluctuate due to changes in ambient temperature, that is, the differential pressure signal can be stabilized.

FIG. 2 is a sectional view of the second embodiment. In the second embodiment, large and small main bodies 11 and 12 are used in place of the main body 1 of the first embodiment, and a protective portion is embedded inside the main body 11. The protective portion is a unit including a protective diaphragm 17 and side plates 15 and 16 that form mortar-shaped spaces 15a and 16a arranged on both sides of the protective diaphragm 17, respectively. Also each body
Sealing diaphragms 13 and 14 are fixed to the left and right end surfaces of 11, 12 respectively, and a cover 39 is fastened with a bolt 40 and a nut 41 via an O-ring 38 to form a pressure receiving portion. Body
Pressure guiding pipes 36, 37 are provided upright on the outer peripheral surface of 11, and the detection unit 20 is connected to the tip end side thereof. The T-shaped hole 13a formed in the main body 11 has a first end opening at the right end surface of the main body 11, a second end communicating with the space 15a, and a third end leading. It communicates with the hole 36a of the pressure tube 36. The hole 14a passing through the body 12 is
It has openings on the left and right end faces of and communicates with the space 16a. Further, the hole 14a communicates with the hole 37a of the conduit tube 37 through a gap between the right end surface of the main body 12 and the bottom surface on the main body 11 side.

The respective pressures received by the respective seal diaphragms 13 and 14 are one from the hole 13a of the main body 11 through the hole 36a of the pressure guiding tube to the corresponding side of the detecting portion 20, and the other from the hole 14a of the main body 12. At the same time, the pressure is transmitted to the corresponding side of the detecting portion 20 through the pressure guide hole 37a, and at the same time, the pressure is transmitted to the spaces 15a and 16a on both sides of the protective diaphragm 6 and, as described in the conventional example, is excessive. The protection function against pressure works. Moreover, the protective diaphragm 17 and the spaces 15a and 16a on both sides thereof (that is, the side plate 1
(5, 16) and the protective part are
Are spaced apart inside the bolt 40 that fastens each cover 19 on both sides of the. Therefore, the bolt 40 due to changes in ambient temperature
The change in the tightening force of the protective diaphragm 17 and each side plate 1
It does not affect the gap between the contact areas of the 5,16 joints. As a result, the differential pressure signal does not fluctuate due to changes in the ambient temperature, and the differential pressure signal can be stabilized.

[0019]

According to the present invention, it is possible to expect an excellent effect that the zero-point fluctuation does not occur and that the differential pressure signal is stabilized. The reason is as follows. Whether the protective portion and the differential pressure detecting portion are arranged outside the pressure receiving portion, or the protective portion is embedded in the pressure receiving portion so as to be located inside the fastening bolt of the pressure receiving portion, and the differential pressure detecting portion is In any case, since the protective portion is located away from the fastening bolts of the pressure receiving portion regardless of whether it is arranged outside the pressure receiving portion, the tightening force of the bolt changes due to the change in ambient temperature. Even
The effect does not extend to the joint between the protective diaphragm and each body on both sides. Therefore, the gap at the contact portion at the joint is not changed. That is, neither the displacement of the protective diaphragm, in other words, the apparent changes in the internal pressure occur.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment according to the present invention.

FIG. 2 is a sectional view of the same second embodiment.

FIG. 3 is a sectional view of a conventional example.

FIG. 4 is a schematic cross-sectional view of a main part showing a problem of a conventional example.

[Explanation of symbols]

 1 main body 2,3 seal diaphragm 2a 3a hole 4,5 side plate 4a, 5a space 6 protection diaphragm 7,8 pressure guide tube 7a, 8a hole 11,12 main body 13,14 seal diaphragm 13a, 14a hole 15,16 side plate 15a, 16a Space 17 Protective diaphragm 36, 37 Pressure guide tube 36a, 37a Hole 38 O-ring 39 Cover 40 Bolt 41 Nut

Claims (3)

[Claims] Claims: 1. A seal diaphragm for receiving each pressure of a differential pressure to be measured is fixed to each end face on both sides of the main body at a peripheral edge portion with a gap in each central portion, to cover each seal diaphragm. And a pressure-receiving part, which is integrally and hermetically fastened to the main body via a bolt at the peripheral edge of the cover; a protective part in which a mortar-shaped space is formed facing each side of the protective diaphragm; a differential pressure detecting part Each of the pressures received by the seal diaphragm is communicated with the corresponding space of the protective part through the inside of the body of the pressure receiving part via the sealed fluid, and is transmitted to the corresponding side of the differential pressure detecting part. In the differential pressure detecting device with the overpressure protection function described above, the protective portion is located away from the fastening bolt of the pressure receiving portion. 2. The differential pressure detecting device according to claim 1, wherein the protective portion and the differential pressure detecting portion are arranged outside the pressure receiving portion. 3. The device according to claim 1, wherein the protective portion is embedded in the pressure receiving portion so as to be located inward of the fastening bolt of the pressure receiving portion, and the differential pressure detecting portion is provided outside the pressure receiving portion. A differential pressure detection device characterized by being installed.