JPH04169830A - Differential-pressure detecting device - Google Patents

Abstract

PURPOSE:To make it possible to suppress the fluctuation of a zero point and the stress generated in a protecting diaphragm by setting the ratio between the diameter of the operating part of each side diaphragm and the diameter of a hole and the ratio between a central diaphragm and the thickness of a plate within specified ranges, respectively. CONSTITUTION:Side diaphragms 62 are laminated on both side surfaces of a central diaphragm 61 and have the same diameter and the same material as those of the central diaphragm 61. The diaphragms 62 have the disk shape. Circular holes 62a are formed at the central parts of the side diaphragms 62. Thus, the friction caused by the deviation in the direction of the radius in the displacement at the central parts between the central diaphragm 61 and the side diaphragms 62 is eliminated. The ratio between the diameter of the operating part of each side diaphragm 62 and the diameter of the hole and the ratio between the central diaphragm 61 and the plate thickness are limited in the ranges of 0.1 - 0.25 and 1.0 - 1.2, respectively. Thus, the maximum values of the stresses which are generated on the central part and the circumference of the operating part of the central diaphragm and on the inner surface of the central hole and the circumference of the operating part of the side diaphragm can be suppressed. In this way, the fluctuation of a zero point and the stress generated in the protecting diaphragm 60 can be suppressed.

Description

[Detailed description of the invention] [Industrial application field]

The present invention provides a detection unit that includes a detection unit that outputs a signal corresponding to a differential pressure to be measured, and a protective diaphragm that is installed externally to the detection unit and protects the detection unit from each introduced pressure that causes a pressure difference. The present invention relates to a differential pressure detection device, and more particularly to a differential pressure detection device improved to suppress zero point fluctuations and stress generated in a protective diaphragm. Note that this differential pressure detection device can be used as a pressure detection device for gauge pressure or absolute pressure because one of the introduced pressures is atmospheric pressure or vacuum.

[Conventional technology]

The conventional device will be described with reference to FIG. 3, which is a sectional view of this device. In FIG. 3, the conventional and conventional devices are roughly divided into a detection section 20 and a protection section 30, which are connected via pressure impulse pipes 6 and 7. The detection section 20 converts the differential pressure to be measured into an electrical signal and outputs it, and the protection section 30 protects the detection section 20 against the introduced pressure, which will be described in detail later. Since the configuration of this detection section 20 is well known,
The explanation will be omitted. Note that there is another conventional device in which the detection section 20 is installed inside the protection section 30;
The purpose of configuring the sensor 0 to be provided externally to the protection section 30 is to prevent the detection section 20 from being affected by the temperature of the measured fluid when the temperature is high. Now, the protection part 30 mainly includes a main body 3L32, a protection diaphragm 3, a seal diaphragm 4, and a 5.0 ring 8.
and a cover 9. Here, the members of the main body 31, 32 and the seal diaphragms 4, 5 having the same name are the same, and there are two O-rings 8 and two covers 9. Main bodies 3L32 are disposed on the left and right sides with the protective diaphragm 3 in between, and are joined to each other at their respective outer peripheries or peripheral edges. In addition, the main body 3L32 has the same recesses 11° and 21, respectively.
, hole 14.24 and hole 45.55 are formed. More specifically, the main body 31 on the right side will be described as follows. The recess 11 is formed coaxially with the left side of the main body 31 in the shape of a pot, the hole 14 passes through the main body 31 along its axis, the hole 45 opens near the outer periphery of the recess 11 on one side, and the hole 45 opens near the outer periphery of the recess 11 on the other. It passes through the pressure guide pipe 6 and communicates with a pressure guide space (not shown) of the detection section 20 . The right side surface of the main body 31 is formed into a wave shape in cross section, and a seal diaphragm 4 having a shape substantially the same as the wave shape is fixed at the periphery of the right side surface of the main body 31 with a space between the seal diaphragm 4 and the right side surface of the main body 31. A force)<-9 is attached via an O-ring 8 to the outer peripheral edge of the sealing diaphragm 4 on the right side of the main body 31. The above is substantially the same for the left main body 32. Then, the space in contact with the seal diaphragm 4°5, the holes 14, 24, the recess IL21 and the hole 45.55.
These spaces are each filled with silicone oil (filling liquid) as a pressure transmitting fluid. The operation of this conventional device is as follows. differential pressure flowmeter,
For example, each inlet pressure (including static pressure) on each side of the orifice
are respectively received by the seal diaphragm 4.5, the respective introduced pressures are applied to the spaces and holes 14.5 in contact with the seal diaphragm 4, respectively. Recessed portion 11. Detection unit 20 through hole 45
, and the space in contact with the seal diaphragm 5, the hole 24° and the recess 21. The pressure is transmitted through the hole 55 to the other pressure guiding space of the detection unit 20 . In addition, the seal diaphragms 4 and 5 have extremely small spring constants (soft <).
The detection diaphragm (not shown) of the detection section has an extremely large spring constant (stiffness<), and the protection diaphragm 3 has a spring constant that is intermediate between the above two values. In the detection unit 20, the differential pressure based on each introduced pressure is converted into an electrical signal by a well-known method, for example, a capacitance method, and is output. The above is a case where the pressure introduction operation is performed normally. However, due to an incorrect operation, the right seal diaphragm 4
If only the protective part 30 is not present, then
The detection unit 20 may receive a large one-sided pressure and the sensor may be destroyed. Even if there is an error in introducing each pressure on both sides of the orifice and only one pressure is received by the seal diaphragm, the protection part 30 protects the detection part 20 by the following operation. - In FIG. 3, if only the sealing diaphragm 4 receives pressure, this pressure is transferred to the hole 14 through the sealed liquid. From the recess 1, on the one hand, via the protective diaphragm 3, the left recess 21. It is transmitted through the hole 24 and inflates the seal diaphragm 5. On the other hand, it is transmitted through the hole 45 to the pressure guiding space on the right side of the detection unit 20 . However, this transmitted pressure is limited to a certain value or less by the seal diaphragm 4 coming into contact with the right corrugated surface of the opposing main body 31, so there is no risk of the sensor being destroyed and the protective function has worked. It turns out.

[Problem to be solved by the invention]

As explained above, in the conventional technology, if the protective diaphragm 3 is made as soft as possible, in other words, if it is made so that it can be largely displaced with a small pressure, the one-sided pressure transmitted to the detection section 20 can be suppressed. Moreover, at this time, the protective diaphragm 3 must be protected from damage by not increasing the stress generated therein. Therefore, conventionally, a method has been adopted in which a plurality of diaphragms are stacked together as a protective diaphragm. However, this method has the problem that due to surface friction between adjacent diaphragms, they do not completely return to the initial position when the applied one-sided pressure is removed, resulting in residual displacement, resulting in zero point fluctuation. There is. An object of the present invention is to provide an improved differential pressure detection device that eliminates the above-mentioned problems of the prior art and suppresses zero point fluctuations and stress generated in the protective diaphragm.

[Means to solve the problem]

In order to solve this problem, the differential pressure detection device according to claim 1 includes: a detection section that outputs a signal according to the differential pressure to be measured; A detection device comprising a protective diaphragm that protects the detection part against pressure, the protective diaphragm comprising: a disk-shaped central diaphragm; laminated on each side of both surfaces of the central diaphragm; It has a circular hole in the central diaphragm, and has the same diameter and the same material as the central diaphragm. Each side diaphragm has a plate thickness ratio (hereinafter referred to as plate thickness ratio) within a predetermined range; The differential pressure detection device according to claim 2 is the device according to claim 1, wherein the hole diameter ratio and the plate thickness ratio are in the range of 0.1 to 0.25, 1.0 to 1.2, respectively. . The differential pressure detection device according to claim 3 is the device according to claim 1, wherein the hole diameter ratio and the plate thickness ratio are in the ranges of 0.3 to 0.5 and 0.9 to 1.0, respectively. . The differential pressure detection device according to claim 4 is the device according to claim 1, wherein the hole diameter ratio and the plate thickness ratio are in the ranges of 0.4 to 0.6 and 0.8 to 0.9, respectively. .

[Effect]

In the differential pressure detection device according to any one of claims 1 to 4, in common, a circular hole formed in the center of the side diaphragm is used to detect a deviation in the radial direction at the time of displacement at the center between the center diaphragm and the side diaphragm. Friction that could otherwise occur is eliminated. In addition, by limiting the ratio of the diameter of the hole to the diameter of the operating part of the side diaphragm (hole diameter ratio) and the ratio of the plate thickness to the center diaphragm (plate thickness ratio) to within a certain range, the central part of the center diaphragm Moreover, the maximum value of each stress occurring on the circumference of the operating portion, on the inner circumference of the center hole of the side diaphragm, and on the circumference of the operating portion can be suppressed.

【Example】

Embodiments of the differential pressure detection device according to the present invention will be described below with reference to the drawings. FIG. 1 is a side sectional view of the protective diaphragm in this first embodiment, and FIG. 2 is the same (front view thereof). In FIG. a side diaphragm 62 located adjacent to a central diaphragm 61 .
Each side diaphragm 62 has a planar disk shape with the same diameter, but while the central diaphragm 61 has no hole in the center, each side diaphragm 62 has a hole 62a in the center.
There is. Therefore, the presence of the hole 62a allows the central diaphragm 61 and the adjacent side diaphragm 62 to
Friction that may occur due to radial deviations during deformation in the center between them is eliminated, and the surface friction forces between each other are reduced. As a result, the protective diaphragm 60 almost completely returns to its initial position when the one-sided pressure acting on it is removed, so that zero point fluctuations are suppressed. By the way, although the protective diaphragm 60 is structurally a three-layer structure, it is operationally equivalent to a two-layer structure. That is, it is the center diaphragm 61 and either side diaphragm 62 that are displaced when subjected to differential pressure. Below, we will analyze in detail the stress generated in the central diaphragm and side diaphragms. The location where the maximum stress occurs in each diaphragm and the direction of the stress are: for the central diaphragm, either ■ radial direction at the center, ■ radial direction on the circumference of the operating part, and for the side diaphragms , (circumferential direction on the circumference of the center hole), or (2) radial direction on the circumference of the operating part. Now, based on the formula for the stress when a disc-shaped member is subjected to pressure perpendicular to its surface, and the assumption that the displacements at each location of the center and side diaphragms are the same,
Deriving each stress in (2) is as follows. Now, h: Thickness of central diaphragm 1: Thickness of side diaphragm a: Radius of operating part b: Radius of circular hole in side diaphragm C: Poisson's ratio of each diaphragm E: Young's modulus of each diaphragm P: Acting difference When expressed as pressure, each stress σl corresponding to the above ■, ■, ■, ■
, σ2. σ3. σ4 is ty1=3(1+ν) (a”(Y2-Yl-Xi)+
b2((b/a)2+41n(a/b))XIIP/8
h2 (Y2-Yl) - (1) o2 = 3 (a2
(X1+Y1-Y2)+b2((b/a)2-2) X
i) P/4h” (Y2-Yl)
, (2) σ3 = 3a” [((1+3ν)+4(
1+ν) (A+ i!, n(a/b))+2(1-v)
) (b/a)2+(1-ν)B(a/b)2] XI
・P/8i2 (Y2-Yl)
...(3)σ4 =3a2(3+ν+4A(1+ν
)(b/a)2-(1-ν)(2(b/a)2+B)
) Xi ・P/8i”(Y2-Yl)-(4)
However, χ1 = (a"-b2)"/64DY1=
(-a'+6a2b"-3b'-12b'j2n(a/
b)-2b"/a")/64D Y2=-(a'-9b'+8a"b"+8A(a"b"
-b')+4(a'B-2b')l n(a/b))
/64Ft) =Eh'/12(1-ν"), F=Ei'/1
2(L-ν2)A =-a" ((1-v X2+a"
/b2)+[(1+3v)+4(1+v)f
n(a/b)) b”/a2)/4 (0-ν)a”
+(1+ν)b2] B =-b2 ((1+ν) (1-41!, n(
a/b)b”/a2) +(1-v)b2/a”)
/ ((1-v)a2+(1+v)b2) formula (
13, (2), (3), (4), b/a, i/h
A computer simulation was performed using the variables as variables, and the following conclusions were obtained. That is, (a) 0.1≦b/a≦0.25, and 1.
0≦i / h≦1,2 (b) 0.3≦b / a≦0.5 and 0.9≦
i/h≦1.0 (C) 0.4≦b/a≦0.6 and 0.8≦
By setting i/h≦0.9, the maximum values of σ1 to σ4 can be suppressed to low values. Next, a numerical comparison will be made between the stress value in the example and the stress value in a conventional single-piece protective diaphragm. The displacement for a unit differential pressure, that is, the spring constant of the protective diaphragm, is the value Kd in the embodiment, and the value in the conventional example is Vd.
Assuming that .
+ε6)XI/(Y2-Yl) ) /16Eh3 =
V/P = π(1-v'')a6/16Et' However, t is the thickness of the conventional single-piece protective diaphragm.Of course, the spring constants of the embodiment and the conventional example must be the same. Therefore, (1+(-1+3ε2-3ε4+εh)Xi/(Y2-
Yl) ) /b'= 1/13
...(5) Also, the maximum stress σ of the protective diaphragm in the conventional example is the stress in the radial direction on the working radius, and is a −3 (a/t) ”P/4
- (6) By eliminating t from each equation (5) and (6) and calculating the value of σ in the cases of (a), (b), and (C) above, this is the protection in the conventional example that should be sought. This is the maximum stress on the diaphragm. In addition, E = 20000 kg/ IIts, ν = 0
．． 3. The calculation results show that the values of σ in cases (a), (b), and (C) above are all approximately 90% or less of the stress value in the conventional example with the same spring constant, and The maximum stress could be suppressed by about 10% or more compared to the conventional example.

【Effect of the invention】

Compared to the prior art, the embodiments of the present invention provide that the protective diaphragm almost completely returns to its initial position when the one-sided pressure acting on it is removed, so that zero point fluctuations are suppressed;
and the maximum stress generated is reduced by about 10% or more compared to the conventional one.
It has a nice effect.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a protective diaphragm according to an embodiment of the present invention, FIG. 2 is a front view thereof, and FIG. 3 is a sectional view of a conventional example. Code explanation: 60: Protective diaphragm, 61: Central diaphragm, 6
2: Side diaphragm, 62a: Hole. Ili! Official Yahuum Danq Dog 1 figure and q Not 2 figure

Claims (1)

[Claims] 1) a detection unit that outputs a signal according to the differential pressure to be measured;
In the detection device, the detection device includes a protective diaphragm that is installed externally to the detection unit and protects the detection unit from each introduction pressure related to the differential pressure, wherein the protection diaphragm includes one central diaphragm having a disk shape. are laminated on each side of both sides of this central diaphragm, have a circular hole in the center, form a disk shape of the same diameter and the same material as the central diaphragm, and have a diameter of the hole relative to the diameter of the operating part. ratio (hereinafter referred to as hole diameter ratio) and the ratio of plate thickness to the central diaphragm (hereinafter referred to as plate thickness ratio)
and a diaphragm on each side, each having a predetermined range. 2) The differential pressure detection device according to claim 1, wherein the hole diameter ratio and plate thickness ratio are in the ranges of 0.1 to 0.25 and 1.0 to 1.2, respectively. . 3) The differential pressure detection device according to claim 1, wherein the hole diameter ratio and plate thickness ratio are in the ranges of 0.3 to 0.5 and 0.9 to 1.0, respectively. . 4) The differential pressure detection device according to claim 1, wherein the hole diameter ratio and plate thickness ratio are in the ranges of 0.4 to 0.6 and 0.8 to 0.9, respectively. .