JPH01110231A - Capacitance type differential pressure measuring apparatus - Google Patents

Abstract

PURPOSE:To enable a reduction in the amount of a sealing liquid along with a better temperature characteristic, by arranging two sheets of center diaphragms closely as each built in a symmetrical construction as a whole. CONSTITUTION:Two center diaphragms 21 and 22 are arranged to face the wall of an internal chamber 11 provided within a body 1 to form separate center chambers 12 and 13. The center diaphragms 21 and 22 and the internal chamber 11 forms a center diaphragm chamber 23. A chamber 411 provided in a disc 41 of a main body is divided into measuring chambers 431 and 432 with a measuring diaphragm 43. Seal diaphragms 611 and 621 are provided outside nest bodies 61 and 62 mounted as opposed to the body 1 and sealing chambers 612 and 622 are formed. When the seal diaphragms 611 and 612 receive a measuring pressure, the measuring diaphragm 43 is displaced through sealing liquids 101-103 to change a capacitance between the measuring diaphragm 43 and a fixed electrode 44.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a capacitive differential pressure measuring device.

More specifically, the present invention relates to a capacitive differential pressure measuring device in which the span of measured pressure does not change due to static pressure.

<Prior Art> FIG. 8 is a diagram illustrating the configuration of a conventional example that has been commonly used.

In the figure, this device mainly includes a differential pressure sensing section 10a1.
First cover flange 11a and second cover flange 12
It is composed of a.

First cover flange 11a and second cover flange 12
a are the first pressure chamber 15a and the second pressure chamber 16a, respectively.
A first measurement fluid having a pressure P1 is introduced into the first pressure chamber 15a through the first pressure introduction hole 13a, and a first measurement fluid having a pressure P1 is introduced into the second pressure chamber 16a through the second pressure introduction hole 14a. A second measuring, constant fluid having a pressure P2 is introduced.

First cover flange 11a and second cover flange 12
a is attached to the differential pressure sensing section 10a via an O-ring.

The differential pressure sensing section 10a mainly includes a first casing 19a.
1 consists of a second casing 20a and a differential pressure transmitter 26a.

A cavity 21a is formed in the first casing 19a, and a first seal diaphragm 22a is formed on the opposite side of the cavity 21a.
is provided. The first seal diaphragm 22a forms a first seal chamber 24a together with the first casing 19a, and is subjected to the action of the pressure P+ introduced into the first pressure chamber 15a. Furthermore, a communication passage 30a is formed in the first casing 19a to communicate the cavity 21a and the first seal chamber 24a.

Further, a differential pressure transmitter 26a is welded to the second casing 20a, and a second seal diaphragm 23a is provided on the opposite side of the differential pressure transmitter 26a. The second seal diaphragm 23a forms a second seal chamber 25a together with the second casing 20a, and is affected by the pressure P2 introduced into the second pressure chamber 16a.

This second casing 20a includes a differential pressure transmitter 2, which will be described later.
A communication path 33a is formed that communicates the second measurement chamber 6a with the second seal chamber 25a. The first casing 19a and the second casing 20a are arranged so that the differential pressure transmitter 26a welded to the second casing 20a is placed in the cavity 21a of the first casing 19a, and at that time, the differential pressure transmitter 26a and the One casing 19a is welded so that a space 29a is formed between the two casings 19a and 19a.

In this way, the differential pressure transmitter 26a is fixedly arranged within the space formed by the first casing 19a and the second casing 20a.

The differential pressure transmitter 26a includes a first housing 27a and a second housing 28a, as shown in an enlarged sectional view in FIG.
has.

A cavity is formed in each of the housings 27a, 28a, and the cavity is filled with insulators 35a, 36a. Fixed electrodes 37a and 38a are provided on opposing surfaces of the insulators 35a and 36a.

A measuring diaphragm 34a is arranged between the first housing 27a and the second housing 28a, and the circumferential surface of the measuring diaphragm is welded to the first housing 27a and the second housing 28a.

Thus, the insulator 35a and the measurement diaphragm 34a constitute a first measurement chamber 42a, and the insulator 36a and the measurement diaphragm 34a constitute a second measurement chamber 43a.

Furthermore, a communication passage 31a for communicating the first measurement chamber 42a and the first sealing chamber 24a via the communication passage 30a is formed in the first housing 27a, and the communication passage 31a and the space 2
A groove 41a communicating with the groove 9a is provided.

Further, a communication passage 32a is formed in the second housing 28a to communicate the second measurement chamber 43a and the second seal chamber 25a via a communication passage 33a.

Thus, the second housing 28a of the differential pressure transmitter is welded to the second casing 20a.

First seal chamber 24a, second seal chamber 25a, communication path 30
The two chambers constituted by a, 31a, 32a, 33a, a first measurement chamber 42a, a second measurement chamber 43a, and an empty ff129a are filled with sealed liquids 101a and 102a.

In the above configuration, when the differential pressure between the measured pressures PI and P2 is within a predetermined measurement range, the seal diaphragm 22
When a and 23a receive measurement pressures PI and P2, the measurement diaphragm 34a is displaced in response to the differential pressure via the sealed liquids 101a and 102a, and the measurement diaphragm 34a and the fixed electrode 37a are displaced.

The capacitance between 38a changes.

As a result, an electrical signal corresponding to the differential pressure between the measured pressures P and P2 is obtained.

Next, when excessive pressure is applied to the first pressure chamber 15a (or second pressure chamber 16a), the measurement diaphragm 34a
Protection against overpressure is provided by the close contact with the

The differential pressure transmitter 26a is disposed in a space 29a formed in the cavity 21a of the first casing 19a by the first casing 19a and the second casing 20a.

Therefore, the outside and inside of the differential pressure transmitter 26a, that is, the space 2
9a, the first measurement chamber 42a, and the second measurement chamber 43a have almost the same pressure through the groove 41a.

Therefore, even if the measured pressures P+ and P2 are high static pressures, the first housing 27a and the second housing 28a will not swell from the inside to the outside.

Therefore, the measuring diaphragm 34a is not subjected to a tensile force in its radial direction due to the static pressure, and the span of the measured differential pressure does not change due to the static pressure.

<Problems to be solved by the invention> However, in such a product, the filling liquid 10
1a is also sealed in the space 29a, the filled liquid becomes unbalanced, and in order to correct this, it is necessary to fill the filled liquid 1.
It is necessary to increase the amount of 02a to maintain balance. As a result, the sealed liquid increases as a whole, and as a result of the sealed liquid layer, the change in the pressure in the sealed chamber when the temperature changes increases, and due to the difference in the volume change of the seal diaphragms on both sides, the zero temperature change becomes large. This results in deterioration of temperature characteristics, etc.

Furthermore, if excessive pressure is applied to the second pressure chamber side, the excessive pressure cannot be effectively prevented.

The present invention solves this problem.

An object of the present invention is to make the entire structure symmetrical, eliminate error factors such as temperature errors, and obtain good characteristics, reduce the volume of the center diaphragm chamber, reduce the amount of sealed liquid, and increase the i! It is an object of the present invention to provide an electrostatic capacitive differential pressure measuring device that is less affected by expansion and contraction, has small hysteresis, and can be made compact.

Means for Solving the Problems To achieve this object, the present invention includes a block-shaped body, an internal chamber provided inside the body, and a block-shaped body provided opposite the wall of the internal chamber. two center diaphragms disposed close to each other and parallel to each other, the outer periphery of a thick ring portion provided at the peripheral edge of the wall of the inner chamber and the center chamber respectively forming a center chamber, the outer periphery of which is welded and fixed to the body; and the center diaphragm. a center diaphragm chamber comprising a center diaphragm chamber, a case having an internal cavity, a disc made of an insulating material installed in the internal cavity, and a metal material attached to the circumferential surface of the disc. A main body consisting of a ring, a chamber provided in the disk, a measurement diaphragm that divides the chamber into two measurement chambers and functions as a moving electrode, and a measurement diaphragm provided on the wall of the measurement chamber opposite to the measurement diaphragm. The body is inserted into an insertion hole provided at one end, the edge of the center diaphragm chamber and the outer peripheral edge of the body are welded and fixed to the insertion hole, and the other end is fixed to the case. a housing, a nest body attached to the housing to face the body with a gap therebetween, a seal diaphragm that is pushed onto the outer surface of the nest body and forms a seal chamber with the nest body; A pack-up nest provided in the nest body to face each other, a communication passage communicating the seal chamber and the center chamber, a cover flange covering an outer surface of the nest body, and a gap between the main body and the inner cavity. A tube is connected at one end to the main body, fixed to the case midway, and connected to the housing at the other end so as to maintain and support the measurement chamber, and the measurement chamber and the center chamber are communicated through the tube, respectively. a communication path, a communication path that communicates the internal cavity and the center diaphragm chamber, and the seal chamber;
A capacitance type differential pressure system characterized by having a liquid sealed in each of three chambers consisting of a center chamber, a center diaphragm chamber, a communication passage, an internal cavity, and a measurement chamber. This constitutes a measuring device.

<Function> In the above configuration, when the differential pressure of the measured pressure is within the predetermined measurement range, when the seal diaphragm receives the measured pressure, the measuring diaphragm is displaced in response to the differential pressure via the sealed liquid. , the capacitance between the measuring diaphragm and the fixed electrode changes.

As a result, an electrical signal corresponding to the differential pressure between the measured pressures is obtained.

Hereinafter, a detailed explanation will be given based on examples.

<Example> FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention.

In the figure, 1 is a body consisting of bodies IA and IB. 11 is an internal chamber provided inside the body 1. 1
11 is a ring-shaped groove provided on the outer periphery of the body 1.

2 and 22 are provided facing the wall of the internal chamber 11, as shown in FIG.
．． 13, and a thick ring portion 2 provided at the peripheral edge.
1, the outer circumference of 221 is welded and fixed to body 1 212.222
and two center diaphragms arranged in close parallel parallel to each other. 23 is the center diaphragm 2, 22
This is a center diaphragm chamber composed of an inner chamber 11 and an inner chamber 11.

3 is a case having an internal space 31.

4 is a disk 4 provided in the internal space 31 and made of an insulating material.
1 and a ring 42 made of a metal material attached to the circumferential surface of a disk 41.

As shown in FIG. 3, 411 is a chamber provided within the disk 41. As shown in FIG. 43, the chamber 411 is divided into two measurement chambers 43, 43
A measuring diaphragm that functions as a two-part moving electrode. 44 is a measurement chamber 43 facing the measurement diaphragm 43.
, 432 are fixed electrodes provided on the walls.

5, the body 1 is inserted into an insertion hole 51 provided at one end, and the edge 231 of the center diaphragm chamber 23 and the body 1
The outer peripheral edge portion 112 of the housing is fixed to the insertion hole 51 by welding, and the other end is fixed to the case 3. 14 is a ring provided between the body 1 and the insertion hole 51.

Numerals 6 and 62 are nest bodies attached to the housing 5 facing the body 1 with a gap 610 maintained therebetween.

Seal diaphragms 61 and 621 are provided on the outer surfaces of the nest bodies 6 and 62 and constitute seal chambers 612 and 622 with the nest bodies 6 and 62.

Reference numerals 613 and 623 designate vari-up nests provided in the nest bodies 61 and 62 opposite to the seal diaphragms 611 and 621.

63 and 64 are the seal chambers 612 and 622 and the center chamber 12.
This is a communication path that connects '13. .

65 and 66 are cover flanges that cover the outer surfaces of the nest bodies 6 and 62.

Reference numeral 45 denotes a tube having one end connected to the main body 1 so as to support the main body 1 in the internal space 31 with a gap maintained, a midway part fixed to the case 3, and the other end connected to the housing 5.

Reference numeral 46 denotes a communication path through which the measurement chambers 43, 432 and the center chamber 12.13 communicate with each other through the tube 45.

Reference numeral 47 is a communication passage that communicates the internal space 31 and the center diaphragm chamber 23.

10, 102.103 are seal chambers 512, 622, gaps 610. Center room 12.13. Center diaphragm chamber 2
3. This is a sealed liquid that is sealed in three chambers each consisting of communication passages 46, 47.63°64, internal cavity 31, and measurement chambers 43 and 432.

In the above configuration, the differential pressure between the measured pressures P+ and P2 is
When it is within the specified measurement range, the seal diaphragm 6
1, 621 receives the measurement pressure, the sealed liquid 101, 1
02.103, the measuring diaphragm 43 is displaced in response to the differential pressure, and the capacitance between the measuring diaphragm 43 and the fixed electrode 44 changes.

Therefore, an electrical signal corresponding to the differential pressure between the measured pressures can be obtained.

Moreover, the pressure in the center diaphragm chamber 23 is
+P2)/2. Therefore, a differential pressure of (Pl-P2)/2 is applied to the center diaphragms 21 and 22.

In addition, the measurement pressure P I is in the measurement chamber 431, and the measurement pressure P I is in the measurement chamber 432.
Measured pressure P2 is applied to the internal space 31 (P1+P2)
Since a pressure of /2 is applied, no static pressure is applied to the disk 41 and ring 42, and the measured pressure is PL.

Only 1/2 of the differential pressure of P2 is applied, and there is no static pressure span shift due to deformation.

As a result, (1) Since the overall structure is symmetrical, the filled liquid 10, 10
The amounts of 2 are balanced and good wet surface properties can be obtained.

(2) The differential pressure applied to the center diaphragms 2 and 22 is 172 compared to the case of two center diaphragms, which is advantageous in terms of stress.

(3) Since the two center diaphragms 2 and 22 are arranged closely together, the amount of filled liquid 103 can be reduced compared to when they are arranged apart, as shown in FIG. The stress range of the diaphragm can be reduced and the size can be reduced.

(4) Only 1/2 of the differential pressure of the measurement pressure is applied to the ring 42, and the filled liquid 101 or 10 on one side is applied to the internal space 31.
This is advantageous compared to the case where 2 is introduced.

(5) Since the body 1 is inserted and fixed into the insertion hole 51 and placed between the nest bodies 6 and 62 with a gap 610, when the cover flanges 65 and 66 are tightened with bolts, the influence of the tightening force is centered. Extending to diaphragms 2 and 22,
It is possible to obtain something without the possibility of span shift occurring.

(6) Joint edge 231 between insertion hole 51 and body 1
Since the outer peripheral edge portion 112 is welded, measurement pressure does not enter the joint, and static pressure due to the measurement pressure does not act on the joint, so the pressure resistance of the housing 5 can be reduced, and the pressure resistance can be reduced. Parts can be made smaller and lighter.

(7) Center diaphragms 2 and 22 in separate bodies I
Since A and IB can be welded separately, the characteristics of each can be checked at the stage after welding, and it can be assembled at a high yield and manufactured at low cost. Furthermore, since a jig that suppresses deformation during welding can be used, a product can be obtained at low cost and with good properties.

(8) Since the center diaphragms 2 and 22 are arranged close to each other, if the center diaphragms are welded together, there is a risk that the passage for the filled liquid 103 will be easily blocked. There isn't.

(9) In the center diaphragms 2 and 22, the outer circumferences of the thick ring parts 21 and 221 provided at the peripheral edges are fixed to the body 1 by welding 212 and 222.
222 does not affect the main body portions of the center diaphragms 2, 22, and the center diaphragms 2, 22 have less hysteresis.

(10) Since the positions of the fulcrums of the center diaphragms 2 and 22 are clearly determined by the thick ring portions 211 and 221, less hysteresis can be obtained.

FIG. 5 is an explanatory diagram of the main part configuration of another embodiment of the present invention.

In this example, welding 212.2 of ring parts 21, 221
Isolated grooves 213° and 223 are provided near the 22 portion.

In this way, the adverse effects of welding 212 and 222 can be more reliably prevented.

FIG. 6 is an explanatory diagram of the main part configuration of another embodiment of the present invention.

In this embodiment, the outer peripheral edge portion 112 and the edge portion 231 are welded by electron beam welding, and as shown in FIG. 7, a method (single pass EBW) in which two locations are simultaneously welded is used. The ring 14 can be omitted.

・〈Effects of the Invention〉 As explained above, the present invention includes a block-shaped body, an internal chamber provided inside the body, and a block-shaped body provided opposite to the wall of the internal chamber. 2, each of which constitutes a center chamber, and the outer periphery of a thick ring portion provided at the peripheral edge is welded and fixed to the body, and are arranged close to each other and parallel to each other;
a center diaphragm chamber composed of the center diaphragm and the internal chamber, a case having an internal cavity, a disk made of an insulating material provided in the internal cavity, and a peripheral surface of the disk. A main body consisting of an attached ring made of a metal material, a chamber provided in the disk, a measuring diaphragm which divides the chamber into two measuring chambers and functions as a moving electrode, and a measuring diaphragm opposite to the measuring diaphragm. The body is inserted into a fixed electrode provided on the wall of the measurement chamber and an insertion hole provided at one end, and an edge of the center diaphragm chamber and an outer peripheral portion of the body are welded and fixed to the insertion hole at the other end. is fixed to the case, a nest body attached to the housing while facing the body with a gap, and a seal diaphragm provided on the outer surface of the nest body and forming a seal chamber with the nest body. a pack-up nest provided in the nest body opposite to the seal diaphragm; a communication passage communicating the seal chamber and the center chamber; a cover flange covering the outer surface of the nest body; and the main body. a tube that is connected to the body at one end, fixed to the case midway, and connected to the housing at the other end so as to be supported with a gap in the internal space; A communication path that communicates with the center chamber, a communication path that communicates the internal space with the center diaphragm chamber, the seal chamber, the gap, and the center chamber.

A capacitance type differential pressure measuring device is constructed, which is characterized by having three chambers each consisting of a center diaphragm chamber, a communication passage, an internal cavity, and a measurement chamber each having a liquid sealed therein. , <1) Since the entire structure is symmetrical, the amount of the sealed liquid is balanced, and good characteristics such as cross-contamination characteristics can be obtained.

(2) The differential pressure applied to the center diaphragm is 1/2 compared to the case of one center diaphragm, which is advantageous in terms of stress.

(3) Since the two center diaphragms are placed closely together, the amount of sealed liquid can be reduced compared to when they are placed apart, the stress range of the center diaphragm can be improved, and the size can be reduced. Can be done.

(4) Only 1/2 of the differential pressure of the measured pressure is applied to the ring, which is advantageous compared to the case where one side of the sealed liquid is introduced into the internal cavity.

(5) The body is inserted and fixed into the insertion hole and placed with a gap in the nest body, so when the cover 7 langes are tightened with bolts, the tightening force will affect the center diaphragm and span shift will occur. You can get something that is not likely to occur.

(6) Since the insertion hole and the body are welded at the joint part, the edge and the outer periphery, the measurement pressure does not enter the joint part, and the static pressure due to the measurement pressure does not enter the joint part. Since this does not work, pressure-resistant marks on the housing can be reduced compared to when measurement pressure is applied, and the pressure-receiving part can be made smaller and lighter.

(7) Since the center diaphragms can be welded to separate bodies, the characteristics of each can be checked at the stage after welding, and the assembly can be performed at a high yield and at low cost. Moreover, since a jig that suppresses deformation during welding can be used, a product can be obtained at low cost and with good properties.

(8) Since the center diaphragms are placed close to each other, if the center diaphragms are welded together,
Although there is a possibility that the passage of the filled liquid is easily blocked, in the present invention,
There is no fear of that.

(9) As for the center diaphragm, the outer periphery of the thick ring part provided at the periphery is welded and fixed to the body.
Welding does not affect the main body of the center diaphragm,
A center diaphragm with less hysteresis can be obtained.

(10) Since the position of the fulcrum of the center diaphragm is clearly determined by the thick ring portion, less hysteresis can be obtained.

Therefore, according to the present invention, the overall structure is made symmetrical, error factors such as temperature errors are eliminated, good characteristics are obtained, and the volume of the center diaphragm chamber is made small, the amount of sealed liquid is reduced, and the sealed Reduces the influence of liquid expansion and contraction.
It is possible to realize a capacitive differential pressure measuring device that is inexpensive, has good characteristics, has small hysteresis, and can be made compact.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the configuration of one embodiment of the present invention, Fig. 2, Fig. 3
FIG. 4 is an explanatory diagram of the effect of FIG. 1; FIG. 5 is an explanatory diagram of the principal part configuration of another embodiment of the present invention;
FIG. 6 is an explanatory diagram of the main part configuration of another embodiment of the present invention, FIG. 7 is an explanatory diagram of the main part configuration of FIG. 6, and FIG. 8 is an explanatory diagram of the configuration of a conventional example commonly used. FIG. 9 is an explanatory diagram of the main part configuration of FIG. 8. , 1A, IB...Body, 101, 102.103.
... Filled liquid, 11 ... Internal chamber, 111 ... Groove, 11
2...Outer peripheral edge, 12.13...Center chamber, 14.
... Ring, 2, 22 ... Center diaphragm, 21, 221 ... Thick ring part, 212.222
...Welding, 23...Center diaphragm chamber, 231
...Edge, 3...Case, 31...Internal void, 4
...Body, 41...Disk, 411...Chamber, 4
2... Ring, 43... Measuring diaphragm, 43,
432...Measurement chamber, 44...Fixed electrode, 45...
Tube, 46.47...Communication path, 5...Housing, 51...Insertion hole, 61°62...Nest body, 610...Gap, 61, 621...Seal diaphragm, 612. 622... Seal chamber, 613.62
3...Backup nest, 63.64...Communication path, 65.66...Cover flange. Figure 4 Figure 5

Claims (1)

[Claims] A block-shaped body, an internal chamber provided inside the body, and a thick ring provided at the periphery of the body, which is provided opposite to the wall of the internal chamber and forms a center chamber with the wall of the internal chamber, respectively. a case having two center diaphragms whose outer peripheries are welded and fixed to the body and are arranged close to each other in parallel; a center diaphragm chamber composed of the center diaphragms and the inner chamber; and an inner space; , a main body consisting of a disk made of an insulating material provided in the internal cavity, a ring made of a metal material attached to the circumferential surface of the disk, a chamber provided within the disk, and two chambers. A measuring diaphragm divided into a measuring chamber and functioning as a moving electrode, a fixed electrode provided on the wall of the measuring chamber opposite to the measuring diaphragm, and a center diaphragm chamber in which the body is inserted into an insertion hole provided on one end side. a housing whose edges and an outer peripheral edge of the body are welded and fixed to the insertion hole and whose other end is fixed to the case; a nest body which is attached to the housing so as to face the body with a gap therebetween; A seal diaphragm provided on the outer surface of the nest body and forming a seal chamber with the nest body, a backup nest provided in the nest body opposite to the seal diaphragm, and communicating the seal chamber and the center chamber. a communication path, a cover flange that covers the outer surface of the nest body, one end of which is connected to the main body so as to support the main body with a gap maintained in the internal space, a midway part is fixed to the case, and the other end is a tube connected to the housing, a communication path that communicates the measurement chamber and the center chamber through the tube, a communication path that communicates the internal cavity and the center diaphragm chamber, and the seal chamber; A capacitance type differential pressure measurement characterized by having a liquid sealed in each of three chambers consisting of a gap, a center chamber, a center diaphragm chamber, a communication passage, an internal cavity, and a measurement chamber. Device.