JPS5831853B2 - Differential pressure measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a first cylindrical housing having a first insulator inside, a second cylindrical housing having a second insulator inside, and the first and second cylindrical bodies. a differential pressure transmitting portion which is sandwiched between a shaped housing and which transmits a differential pressure from a measuring diaphragm which forms a measuring chamber between the first and second insulators; a casing in which a pressure transmitter is disposed and an internal space thereof communicates with a measurement chamber of the differential pressure transmitter; and two objects to be measured that form a first pressure receiving chamber and a second pressure receiving chamber and are under different pressures. A first fluid passage and a second fluid that communicate between a first pressure receiving diaphragm and a second pressure receiving diaphragm each receiving fluid pressure, the first and second pressure receiving chambers, and each measurement chamber of the differential pressure transmitting section. The present invention relates to a differential pressure measuring device including a passage, a measuring chamber of the differential pressure transmitting section, an internal cavity, and a sealed liquid filled in each pressure receiving chamber.

When two insulators are placed facing each other with a measuring diaphragm in between, metal foil is provided on each side of the insulator facing the measuring diaphragm, and different pressures are applied to each side of the measuring diaphragm. Differential pressure measuring devices are known which detect the electrical capacitance change occurring between a measuring diaphragm and a metal foil and measure the difference in pressure acting on both sides of the measuring diaphragm based on this capacitance change.

However, a drawback of such a differential pressure measuring device is that a change in the measured differential pressure span occurs due to static pressure.

That is, the outer peripheral surface of the housing having an internal space formed by an insulator is at atmospheric pressure, but the inside of the housing, that is, the first measurement chamber and the second measurement chamber, is at pressures PI, P.
2 acts and therefore high static pressure (e.g. 100 #/d
) to be put down.

Therefore, in the housing, a force tends to expand outward from the first and second measurement chambers inside, and the housing becomes slightly larger.

The rate at which the housing becomes larger depends on the magnitude of the high static pressure acting on the first measurement chamber and the second measurement chamber.

The fact that the housing is larger means that
The measuring diaphragm is stretched in its radial direction, so that it stiffens in accordance with the tension.

Therefore, even if the differential pressure between pressures PI and P2 is the same value,
When the magnitudes of the pressures PI and P2 are different, the amount of deformation of the measuring diaphragm is different, and the capacitance change between the measuring diaphragm and the metal foil is detected as a different value.

That is, in the first example, pressure P1 is 49 kg/d, pressure P2
is 50#/ai', and in the second example the pressure P1 is 99
Assume that #/ate1 pressure P2 is 100 kg/d.

In this case, compared to the first example, in the second example, the static pressure acting on the first measuring chamber and the second measuring chamber is higher, and therefore the force that inflates the housing is greater, causing the measuring tire flammable The tensile force on the

Therefore, compared to the first example, the measured diaphragm is harder in the second example, and the amount of deformation thereof is smaller.

Therefore, despite the same differential pressure, the change in capacitance in the second example is smaller than the change in capacitance in the first example.

For these reasons, this pressure measuring device
There is a drawback that the span of the output signal (change in capacitance) changes depending on the magnitude of the static pressure acting on the first measurement chamber and the second measurement chamber, despite the same differential pressure.

FIG. 1 shows a conventional example of a differential pressure measuring device for measuring the difference between two pressures, which was designed to eliminate this drawback.

In the figure, the differential pressure measuring device mainly includes a differential pressure sensing section 1, a first
It is composed of a lid 2 and a second lid 3.

The first lid body 2 and the second lid body 3 each have a first pressure chamber 4 and a second pressure chamber 5. A second fluid to be measured having a pressure P2 is introduced into the second pressure chamber 5 via a second pressure introduction hole 7.

The first fluid to be measured and the second fluid to be measured may be liquid or gas.

The first lid 2 and the second lid 3 are welded to the differential pressure sensing section 1.

Note that 8 and 9 are 0-rings.

The differential pressure sensing section 1 mainly includes a first casing 10 and a second casing 10.
It is composed of a casing 11 and a differential pressure transmitter 12.

A cavity 13 is formed in the first casing 10, and a first pressure receiving diaphragm 14 is provided on the opposite side of the cavity 13.

The first pressure receiving diaphragm 14 forms a first pressure receiving chamber 15 together with the first casing 10 and is subjected to the action of the pressure P1 introduced into the first pressure chamber 4.

Furthermore, a liquid passage 16 is formed in the first casing 10 to communicate the cavity 13 and the pressure receiving chamber 15.

Further, a differential pressure transmitter 12 is welded to the second casing 11, and a second pressure receiving diaphragm 18 is provided on the opposite side of the differential pressure transmitter 12.

The second pressure receiving diaphragm 18 forms a second pressure receiving chamber 19 together with the second casing 11 and is subjected to the action of the pressure P2 introduced into the second pressure chamber 5.

A liquid passage 20 is formed in the second casing 11 and communicates the second measurement chamber 30 of the differential pressure transmitter 12 with the second pressure receiving chamber 19 .

The first casing 10 and the second casing 11 are arranged such that the differential pressure transmitter 12 welded and fixed to the second casing 11 is disposed in the cavity 13 of the first casing 10. 1 casing 10 so that a space 21 is formed between them.

In this way, the differential pressure transmitter 12 is connected to the first casing 10.
and the second casing 11.

The differential pressure transmitter 12 has a first housing 22 and a second housing 23, each of which has a cavity formed therein, and an insulator 24, 25 such as glass or porcelain in the cavity. is filled.

One surface of each of the insulators 24, 25 is formed in the form of a spherical section, and a metal foil 26, 27 serving as a capacitor plate is provided on each of the spherical sections.

The first housing 22 and the second housing 23 are formed substantially symmetrically in plane, and are assembled so that the metal foils 26 and 27 face each other.

A measuring diaphragm 28 is disposed in the middle thereof and is welded and fixed to the first housing 22 and the second housing 23.

Thus, a first measuring chamber 29 is constituted by the spherical cut surface of the insulator 24 and the measuring diaphragm 28, and a second measuring chamber 3 is constituted by the spherical cut surface of the insulator 25 and the measuring diaphragm 28.
0 is configured.

Furthermore, the first housing 22 includes a first measurement chamber 29 and a first measurement chamber 29 .
A liquid passage 31 is formed to communicate with the first pressure receiving chamber 15 of the casing 10 via the liquid passage 16, and furthermore, this liquid passage 31 and the space 21 formed in the cavity 13 of the first casing 10 are connected. A communicating groove 32 is provided.

The second housing 23 also includes a liquid passage 3 that communicates the second measurement chamber 30 and the second pressure receiving chamber 19 via the liquid passage 20.
3 is formed.

A second housing 23 of the differential pressure transmitter 12 is fixed to the second casing 11 by welding.

The first pressure receiving chamber 15, the first measurement chamber 29, the space 21 and the second
The pressure receiving chamber 19 and the second measurement chamber 30 are filled with an enclosed liquid such as silicone oil by means not shown.

Next, the functions of the above configuration will be explained.

The differential pressure transmitter 12 is arranged in a space 21 formed in the cavity 13 of the first casing 10 by the first casing 10 and the second casing 11.

Therefore, in this differential pressure transmitter 12, there are
and the second measuring chamber 30 are controlled by substantially the same pressure via the groove 32.

Therefore, no matter how high the pressures PI and P2 are, the first housing 22 and the second housing 23 will not swell outward from the inside thereof.

Therefore, the span of the measured differential pressure does not change due to the radial tensile force of the measuring diaphragm 28 due to static pressure.

However, the inventors manufactured this measuring device and
After conducting a number of experiments, it was determined that the measuring diaphragm 28 was still subject to span errors due to static pressure.

Therefore, as a result of repeatedly conducting various studies and numerous experiments, the inventors of the present invention found that the causes of this were the first and second causes.
The housings 22 and 23 are made of metal, and the power cylinder 1
Furthermore, it has been determined that the second insulators 24 and 25 are made of glass or ceramic.

That is, the amount of compression of an insulator due to a high static pressure is greater than the amount of compression of a metal due to the same static pressure.

Therefore, when the first and second insulators 24.25 are packed inside the first and second housings 22.23,
The amount of compression of the first and second housings 22,23 is
The amount of compression is greater than when the first and second housings are individually subjected to the action of static pressure.

The measuring diaphragm 28 is also made of metal and is compressed by static pressure.

Therefore, if the first and second housings 22.23 are not filled with the first and second insulators 24.25, the first and second housings 22.23 and the measuring diaphragm 28 have the same compression. Since the measured diaphragms 28 have different initial tension lengths, span errors due to static pressure do not appear.

However, as described above, if the first and second housings 22.23 are filled with insulators, the first and second housings 22.23 and the first and second insulators 24. The unitary part 25 exhibits a greater compression than the first and second housings 22, 23 alone would have, and therefore is more compressed than the measuring diaphragm 28.

This causes the measurement diaphragm 28 to slacken, resulting in a span error due to static pressure.

This means that when the first and second housings 22.24 exist alone, the amount of compression of the unit component in which the first and second insulators 24.25 are filled inside the first and second housings 22.23 is It is considered that this can be avoided if the amount of compression becomes equal to the amount of compression.

However, in order to do so, the first and second insulators 2
The Young's modulus (El) of 425 must match the Young's modulus [El) of the first and second housings 22.23.

However, the Young's modulus (E2) is the Young's modulus (El) of the metal.
It is very difficult to select an insulator equal to .

The span error due to static pressure will be explained a little more based on FIG. 2.

FIG. 2 shows a schematic diagram of the housing and insulator subjected to static pressure in FIG. 1, with A being a side sectional view and B being a front sectional view.

In the figure, the static pressure is P, the pressure at the interface between the first housing 22 and the first insulator 24 is Pl, the Young's modulus and Poisson's ratio of the housing 22 are E2, V2, the Young's modulus and Poisson's ratio of the insulator 24 are If the compression amount of the peripheral edge of the housing 22 welded to the measurement diaphragm 28 (not shown) is △12, then 7 for the amount △12 is obtained.
The amount of compression Δld of the measuring diaphragm 28 is where Ed and Vd are the Young's modulus and Poisson's ratio of the measuring diaphragm 28.

Therefore, the span error e due to static pressure is However, εa is the tension of the measuring diaphragm 28.

By applying specific numerical values to this fourth equation, the following equation is obtained.

e-(0,2-2%)/1o okVd...---
---(5) This fifth equation shows that an error e of 0.2 to 2% occurs at a static pressure of 100 kg/atj.

This error e is due to the difference between the housing 22 and the insulator 24, which are foreign substances.
This was an unavoidable error when forming a composite under high static pressure.

However, as a pressure measuring device having static pressure, the value of this error e could not be ignored.

Although the first housing 22 and first insulator 24 of the differential pressure transmitter 12 in FIG. 1 have been described, the second housing 23
The same applies to the second insulator 25.

In view of the above points, the present invention has been developed so that the difference in the materials of the housing and the insulator causes a difference in the amount of compression between the housing and the measuring diaphragm under static pressure, and this difference in the amount of compression causes the measuring diaphragm to It is an object of the present invention to provide a differential pressure measuring device of this type which eliminates the disadvantage of the prior art that span error occurs due to static pressure due to slackening of the span.

According to the present invention, the present invention provides a first cylindrical housing having a first insulator therein, a second cylindrical housing having a second insulator therein, and a first cylindrical housing having a second insulator therein. a measurement diaphragm sandwiched between the housing and the second cylindrical housing, forming a first measurement chamber with the first insulator and a second measurement chamber with the second insulator; , a casing having an internal cavity in which a unit consisting of the first cylindrical housing, the second cylindrical housing and the measuring diaphragm is arranged, the internal cavity of the casing and the A first passage communicating with the first measurement chamber or the second measurement chamber is provided, the first cylindrical housing communicates with the first measurement chamber, and the first cylindrical housing is compressed by static pressure. a first static pressure compensating groove is provided in the second cylindrical housing to prevent the second measuring cavity from being compressed by the static pressure; A second static pressure compensation groove is provided to prevent the first measurement chamber and the second
This is achieved by providing passages for introducing different pressures to be measured into the measurement chamber.

In particular, in the present invention, the static pressure compensating groove is a plurality of grooves formed at the boundary between the housing and the insulator and extending along the axial direction of the housing.

Alternatively, the housing is a cylindrical housing having a bottom, the insulator is a cylindrical insulator having a protrusion on the surface opposite to the measuring diaphragm, and the inner diameter of the housing is the outer diameter of the insulator. Formed larger than the diameter,
Moreover, a through hole is provided in the bottom of the housing, and the protrusion of the insulator is joined to the through hole, and at this time, the annular groove formed between the insulator and the housing is used as a static pressure compensating groove. It will be done.

Yet another static pressure compensating groove is an annular groove formed in the housing itself, near the interface between the housing and the insulator.

Next, embodiments of the present invention will be described in detail based on the drawings.

FIG. 3 shows a schematic configuration diagram of a differential pressure measuring device according to the present invention.

In the figure, parts having the same functions as in FIG. 1 are designated by the same reference numerals.

The differential pressure sensing section 1A mainly includes the first casing 10 and the second casing 10.
It is composed of a casing 11 and a differential pressure transmitter 34.

This differential pressure transmitter 34 is hermetically joined within the space 13 formed by the first casing 10 and the second casing 11.

First, the differential pressure transmitter 34 is connected to the first and second housings 35.
36, each of these housings 35, 36 has a cavity formed therein, and this cavity is filled with insulators 37, 38 such as glass or porcelain.

One surface of each of the first and second insulators 37, 38 is formed into a spherical shape, and metal foils 26, 27 each functioning as a capacitor plate are provided on this surface and assembled so as to face each other.

A measuring diaphragm 28 is arranged in between and is welded and fixed to the first and second housings 35, 36.

A first measurement chamber 29 is constituted by the spherical cut-out surface of the insulator 37 and the measurement diaphragm 28, and a second measurement chamber 30 is constituted by the spherical cut-out surface of the insulator 38 and the measurement diaphragm 28.

Further, in the first and second housings 35 and 36o, a plurality of grooves 39 and 139 extending along the axial direction are provided at the boundaries between the first and second insulators 37 and 38.

The groove 39 provided in the first housing 35 is connected to the first measurement chamber 2.
9 , and the groove 1 provided in the second housing 36
39 communicates with the second measurement chamber 30.

Next, FIG. 4 shows a schematic diagram of a main part of an embodiment of the present invention shown in FIG. 3, in which (A) is a side sectional view and (B) is a front sectional view.

The first housing 35 is shown in FIG.

In the figure, a plurality of grooves 39 are formed on the inner circumference of the first housing 35.
is provided at the boundary with the first insulator 37.

This groove 39 communicates with the first measurement chamber 29 .

This groove 39 acts as a static pressure compensating groove that compensates for the influence of static pressure acting on the first housing 35.

That is, due to the groove 39, substantially equal static pressure P acts on the outer wall surface and the inner wall surface of the first housing 35, thereby reducing the compression of the first housing 35.

As a result of experiments by changing the number and dimensions of the grooves 39, the error e with respect to the compression amount of the measurement diaphragm 28 was approximately 0.2%/
100#/at? could be reduced to a certain degree.

Note that similar grooves 139 are provided in the second housing 36 and the second insulator 38 as static pressure compensating grooves.

Next, FIG. 5 shows a schematic configuration diagram of another embodiment of the present invention,
A is a side sectional view, and B is a front sectional view.

In the figure, the first and second housings 40, 41 have a bottom portion 42.
.

The inner diameters of the first and second housings 40.41 are made larger than the outer diameters of the first and second insulators 44.45 to form annular grooves 48, 48A.

and the bottom parts 42 and 43 of the first and second housings 40 and 41
A through hole 49.49A is provided in the.

This through hole 49° 49A has first and second insulators 44, 4
The protrusions 46 and 47 of No. 5 are joined by baking or brazing.

At this time, the grooves 50.51 are radial grooves provided on the side surfaces of the first and second insulators 44.45.

The grooves 48.48A introduce static pressure from the first and second measurement chambers 29°304, so they serve as static pressure compensation grooves.
The influence of the amount of compression due to static pressure in the first and second housings 40 and 41, which is caused by filling the first and second insulators 44 and 45 made of a different material from that of the housing 40 and 41, is reduced.

Note that the first and second parts bonded in the through holes 49 and 49A
Since the protrusions 46 and 47 of the insulators 44 and 45 have smaller outer diameters than the first and second insulators 44 and 45, the protrusions 46 and 47
The amount of compression that occurs in the first and second insulators 44 .
The amount of compression that occurs at the periphery of 45 is smaller.

Therefore, the influence of the compression amount due to the static pressure of the first and second housings 40, 41 in the protrusions 46, 47 is ignored.

Next, FIG. 6 shows a schematic configuration diagram of still another embodiment of the present invention, in which A is a side sectional view and B is a front sectional view.

In the figure, the first and second housings 53 and 54 are formed into cylindrical shapes, and annular grooves 55 and 56 are formed near the interfaces with the first and second insulators 37 and 38.

This tension groove 55, 56? This is the first and second measurement room 29.3
Since static pressure is introduced by 0, the influence of the amount of compression due to the static pressure in the first and second housings 53 and 54 caused by filling the first and second insulators 37 and 38 as static pressure compensating grooves is as follows. reduced.

Therefore, as a result of the experiment, the annular groove 55,56 reduces the error e from the compression amount of the measured diaphragm 28 by approximately 062%/100k.
g/att.

As described above, according to the present invention, no matter how the high static pressure caused by the measured differential pressure of the differential pressure transmitter changes, the measuring diaphragm will not receive any tensile force in the radial direction, and the housing will not The amount of compression of the housing due to the high static pressure caused by the difference in material from the insulator can be brought close to the amount of compression of the measuring diaphragm.

Specifically, the amount of compression of the housing can be reduced by using a cylindrical housing having a bottom or a plurality of static pressure compensation grooves formed at the boundary between the housing and the insulator and extending along the axial direction of the housing, and this housing. a static pressure compensating groove formed in an annular shape with the inner diameter of the housing larger than the outer diameter of the insulator, or a static pressure compensating groove that is provided in the housing and is connected to the insulator of the housing. This is achieved by an annular static pressure compensating groove formed near the boundary surface of the .

Therefore, the measuring diaphragm is not loosened, and therefore the span error due to static pressure is eliminated, and the effect is very significant.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a conventional example of a differential pressure measuring device, and Fig. 2 is a schematic configuration diagram of a housing and an insulator that receive static pressure in Fig. 1, where A is a side sectional view and B is a front sectional view. 3 shows a schematic configuration diagram of a differential pressure measuring device according to the present invention, and FIG. 4 shows a schematic configuration diagram of an embodiment of the present invention in FIG. 3, where AI is a side sectional view and B is a front sectional view. 5 shows a schematic configuration diagram of another embodiment of the present invention, A is a side sectional view, B is a front sectional view, and FIG. 6 is a schematic configuration diagram of still another embodiment of the present invention. , A is a side sectional view, and B is a front sectional view. 1A: differential pressure sensing section, 10: first casing, 11: second
Casing, 13: Vacant space, 14: First pressure receiving diaphragm, 18: Second pressure receiving diaphragm, 28: Measuring diaphragm, 29: First measuring chamber, 30,: Second measuring chamber, 31,3
3: Fluid passage, 34: Differential pressure transmitter, 35: First housing, 36: Second housing, 37: First insulator, 38:
Second insulator, 39, 139: Groove, 40: First housing, 41: Second housing, 42.43: Bottom, 44
: first insulator, 45: second insulator, 46, 47 protrusion, 4
8 48A: groove, 53: first insulator, 54: second insulator, 55, 56: annular groove.

Claims (1)

[Claims] 1. A first cylindrical housing having a first insulator inside, a second cylindrical housing having a second insulator inside,
and a differential pressure transmitter comprising a measurement diaphragm sandwiched between the first and second cylindrical housings and forming measurement chambers between the first and second insulators, and an internal cavity. A casing in which the differential pressure transmitter is disposed in an internal cavity and in which the internal cavity communicates with a measurement chamber of the differential pressure transmitter, and a first pressure receiving chamber and a second pressure receiving chamber, respectively, and are different from each other. between a first pressure receiving diaphragm and a second pressure receiving diaphragm each receiving the pressure of two measured fluids under pressure, the first and second pressure receiving chambers, and each measurement chamber of the differential pressure transmitting section, respectively. The first and second cylindrical housings include a first fluid passage and a second fluid passage that communicate with each other, and a sealed liquid filled in a measurement chamber, an internal cavity, and each pressure receiving chamber of the differential pressure transmitting unit. The first and second cylindrical bodies are connected to respective measurement chambers of the differential pressure transmitter at respective boundaries between the first and second cylindrical housings and the first and second insulators. A differential pressure measuring device characterized in that a plurality of grooves are formed each extending along the axial direction of a shaped housing. 2. A first cylindrical housing having a first insulator inside, a second cylindrical housing having a second insulator inside,
and a differential pressure transmitter comprising a measurement diaphragm sandwiched between the first and second cylindrical housings and forming measurement chambers between the first and second insulators, and an internal cavity. A casing in which the differential pressure transmitter is disposed in an internal cavity and in which the internal cavity communicates with a measurement chamber of the differential pressure transmitter, and a first pressure receiving chamber and a second pressure receiving chamber, respectively, and are different from each other. A first pressure receiving diaphragm and a second pressure receiving diaphragm each receiving the pressure of two fluids to be measured under pressure.
A pressure receiving diaphragm, a first pressure receiving chamber, and a first pressure receiving chamber communicating with each measurement chamber of the differential pressure transmitting section.
The first and second cylindrical housings include a fluid passageway, a second fluid passageway, and a sealed liquid filled in a measurement chamber, an internal cavity, and each pressure receiving chamber of the differential pressure transmitting unit, and the first and second cylindrical housings have a bottom portion. constituted by a cylindrical housing, and the first
and the second insulator is composed of a cylindrical insulator having a protrusion on a surface opposite to the surface facing the measurement diaphragm,
The inner diameters of the first and second cylindrical housings are formed larger than the outer diameters of the first and second insulators, and through holes are provided at the bottoms of the first and second cylindrical housings, respectively, The protrusions of the first and second insulators are respectively joined to the through holes of the first and second cylindrical housings, and the first and second insulators and the first and second cylindrical housings are connected to each other. A differential pressure measuring device characterized in that an annular groove is formed between the two. 3. A first cylindrical housing having a first insulator inside, a second cylindrical housing having a second insulator inside,
and a differential pressure transmitter comprising a measurement diaphragm sandwiched between the first and second cylindrical housings and forming measurement chambers between the first and second insulators, and an internal cavity. A casing in which the differential pressure transmitter is disposed in an internal cavity and in which the internal cavity communicates with a measurement chamber of the differential pressure transmitter, and a first pressure receiving chamber and a second pressure receiving chamber, respectively, and are different from each other. A first pressure receiving diaphragm and a second pressure receiving diaphragm each receiving the pressure of two fluids to be measured under pressure.
A pressure receiving diaphragm, a first pressure receiving chamber, and a first pressure receiving chamber communicating with each measurement chamber of the differential pressure transmitting section.
The first and second cylindrical housings themselves include a fluid passageway, a second fluid passageway, and a sealed liquid filled in a measurement chamber, an internal space, and each pressure receiving chamber of the differential pressure transmitter, and the first and second cylindrical housings themselves include: A differential pressure measuring device characterized in that annular grooves are formed near respective interfaces with the first and second insulators, each communicating with each measurement chamber of the differential pressure transmitter.