JPH0269631A - Differential pressure measuring instrument - Google Patents

Abstract

PURPOSE:To reduce the occurrence of zero points and span shifts and to improve the humidity characteristics of a differential pressure measuring instrument and, at the same time, to improve the static pressure protecting effect of the instrument with a simple structure by providing a space corresponding to a center chamber in a housing and using an enclosed liquid necessary for measuring differential pressures as the enclosing liquid surrounding a differential pressure sensor. CONSTITUTION:When a differential pressure is applied on a seal diaphragm 31, the inside of a center diaphragms 74 is deformed to have a recessed surface in accordance with the rigidity and transmits the differential pressure to a differential pressure sensor 40 through an enclosed liquid 54. Thus the displacement proportional to the differential pressure is detected as a change in the electrostatic capacity between a measuring diaphragm 422 and fixed electrodes 425 and 426 and the detected change is converted into an electric signal. Since a high static pressure is applied not only to 1st and 2nd measuring chambers 423 and 424, but also to an internal chamber 732 when the high static pressure is applied as a measurement pressure, the sensor 40 is put in the static pressure and no distortion and span variation caused by the static pressure are produced in the sensor 40. Moreover, no zero point nor span shift take place even when the tightening force of a cover flange has secular change.

Description

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

More specifically, the present invention relates to an improvement in a differential pressure measuring device that can reduce zero point and span shifts, improve temperature characteristics, and provide static pressure protection with a simple configuration.

<Prior Art> FIG. 2 is an explanatory diagram of the structure of the invention related to the earlier application of Japanese Patent Application No. 62-259121 entitled "Capacitance Type Differential Pressure Measuring Device" filed on October 14, 1988.

In the figure, 1 is a block-shaped body, 11 is a body 1
An internal chamber 2 provided inside is a center diaphragm that divides the internal chamber 11 into two center chambers 21 and 22.

A seal diaphragm 31 and 32 is provided at the center of the outer surface of the body 1 and forms the seal chambers 311 and 321 with the body 1. 312, 322 are seal diaphragms 3
This is a pack up nest provided in the body 1 opposite to 1.32.

Reference numerals 33 and 34 designate ring-shaped annular diaphragms that are provided concentrically with the seal diaphragms 31 and 32 at the outer edge portion of the outer surface of the body 1 and constitute annular chambers 331 and 341 with the body 1. 332, 342 are diaphragms 33, 34
This is a pack-up nest provided in the body 1 opposite to the pack-up nest.

Reference numeral 12 denotes a communication hole that communicates the center chamber 21, 22 with the seal chambers 311, 321.

4 is a housing having an internal cavity 41;

42 is a main body provided in the internal cavity 41.

421 is a chamber provided inside the main body 42.

422 divides the chamber 421 into two first. Second measurement chamber 423.4
At 24 minutes is a measuring diaphragm which acts as a moving electrode. 425 and 426 are connected to the first diaphragm 425 and 426 through insulators 427 and 428, facing the measurement diaphragm 422. This is a fixed electrode provided on the wall of the second measurement chamber 423,424.

43 has one end connected to the main body 42 so as to support the main body 42 with a gap maintained in the internal space 41, and the middle part is connected to the housing 4.
and the other end is connected to the body 1, and the center chamber 21.
22, respectively.

Reference numeral 44 is a connecting pipe that communicates the internal space 41 with the annular chambers 331 and 341, respectively.

5 is a cover flange.

51, 52, 53, seal chambers 311, 321, communication hole 12, center chambers 21, 22, annular chamber 331, 341, connecting pipe 44, tube 43, internal space 41, first. 2nd'
a fixed room 423, 424. ! : In three chambers consisting of
Each is an encapsulated incompressible liquid.

In this case, silicone oil is used.

6 is provided in the internal space 41 and connects the housing 4 and the tube 4.
It is a filling body that is arranged with a slight gap from the housing 4 and has a coefficient of thermal expansion smaller than that of the housing 4.

In this case, the filling body 6 is made of two filling rod parts 61 as shown in FIG. 3, and as shown in FIG. 4, the two pieces are combined and arranged so as to hold the main body 42.

In the above configuration, the differential pressure applied to the seal diaphragms 31 and 32 is transmitted to the internal chamber 11 via the communication hole 12. Furthermore, the first tube passes through the tube 43. Second measurement chamber 4
23,424 and displaces the measuring diaphragm 422.

A displacement proportional to this differential pressure is detected as a change in capacitance between the measurement diaphragm 422 and the fixed electrodes 425, 426, and converted into an electrical signal.

Next, when a high static pressure measurement pressure is applied, the first. High static pressure is applied to the second measurement chambers 423, 424, and high static pressure is also applied to the diaphragms 33, 34, and the connecting pipe 4
4, static pressure is applied to the internal cavity 41, so that the main body 42
will be placed under static pressure and the measuring diaphragm 4
22, no strain occurs due to static pressure, so span fluctuations due to static pressure do not occur.

On the other hand, when excessive pressure is applied, the sealed liquid 51, 52 in the seal chamber 311 or 321 on the side to which the excessive pressure is applied is completely discharged. This sealed liquid 51 or 52 is absorbed by the displacement of the center diaphragm 2.

As the seal diaphragms 33 and 34 are seated on the pack-up nest 312 and 322, the sealed liquid 51 and 52 no longer move, and no excessive pressure is applied to the measurement diaphragm 422.
13i from overpressure.

When excessive pressure is applied, the side of the annular diaphragm 33 or 34 to which the excessive pressure is applied is seated on the pack-up nest 332 or 342, but the annular diaphragm on the side to which no excessive pressure is applied swells, so that the internal space 41 is The pressure rise is
Small enough to be ignored.

The filling liquid 53 of the internal cavity 41 is connected to the annular chambers 331, 341, and the tubular diaphragms 33, 34 are separated from the sealing diaphragms 31, 32, so that the filling liquid 53 does not take part in the measurement.

Therefore, the characteristics of the tubular diaphragms 33 and 34 do not directly affect the differential pressure measurement, so a large degree of freedom in design can be obtained.

As a result, (1) Preventing overpressure hysteresis.

When excessive pressure is applied, the amount of movement of the enclosures [51, 52 until they are seated on the seal diaphragms 31, 32 or the backup nests 312, 322 is absorbed by the displacement of the center diaphragm 2; , no overpressure is directly applied and the measuring diaphragm 422 is protected from overpressure.

Therefore, the occurrence of hysteresis in the measurement diaphragm due to excessive pressure can be reduced.

(2) Prevention of errors due to tightening of the cover flange 5.

Since the sensor main body part sensitive to mechanical disturbance is placed separately from the pressure receiving part and supported by the tube 43, it is possible to prevent errors caused by tightening of the cover flange 5 to the main body 1.

(3) Preventing temperature errors.

Since the sensor main body portion and the pressure receiving portion are placed separately and supported by the tube 43, it is possible to prevent temperature errors caused by differences in thermal expansion coefficients between the pressure receiving portion and the sensor main body portion.

Further, since the filling body 6 is arranged in the internal space 41, the amount of the filled liquid 53 is small, and the volume variation of the filled liquid 53 due to temperature is small.

Furthermore, due to the difference in thermal expansion coefficient between the housing 4 and the filling body 6, volume fluctuations in the sealed liquid 53 can be absorbed.

As a result, a capacitive differential pressure measuring device with an expanded usable temperature range can be obtained.

<Problems to be Solved by the Invention> However, such a device has the following drawbacks.

(1) The body 1 is divided into two parts and welded at the center.

Therefore, the rigidity becomes low, and the body 1 deforms due to a change in force when tightening the bolts of the cover 7 flange, and the neutral position and spring constant of the center diaphragm 2 and the seal diaphragms 31 and 32 change.

As a result, the bolts become loose due to aging, causing changes in the zero point and span.

(2) The filling liquid 53 is used to place the sensor body under static pressure and prevent excessive force from being applied to the sensor body when static pressure is applied. Due to the need to reduce the size of the diaphragm 33, 34, the structure becomes complicated, such as the need for a filling body 6.
Therefore, if the outer diameter of the body 1 is the same, there is a limit to the outer diameter of the seal diaphragms 31 and 32.
It has drawbacks such as being a constraint on obtaining good characteristics.

(The smaller the rigidity of the seal diaphragm, the better; increasing the outer diameter is most effective.) The present invention solves these problems.

An object of the present invention is to provide a differential pressure measuring device that can reduce zero point and span shifts, improve temperature characteristics, and provide static pressure protection with a simple configuration.

<Means for Solving the Problems> In order to achieve this object, the present invention includes a block-shaped body, and a first . a seal diaphragm forming a second seal chamber; a pack-up nest provided on the body opposite to the seal diaphragm; a cover flange covering an outer surface of the body; and a housing having one side attached to the body. , a support that is attached to one side of the body and is disposed with a gap in the recess and that forms the recess, the first center chamber, and the inner chamber. a pedestal, a ring-shaped groove provided on the peripheral surface of the support pedestal, a cylindrical center diaphragm provided covering the groove and constituting the groove and a second center chamber, and a cylindrical center diaphragm provided in the inner cavity. 1. A differential pressure sensor comprising a second measurement chamber and a sensor element; one end is connected to the differential pressure sensor so as to support the differential pressure sensor in the internal space with a gap therebetween; A tube connected to the support stand and communicating with the first measurement chamber, a communication hole provided in the differential pressure sensor and communicating the second i111 fixed chamber with the internal chamber, and a first seal chamber provided in the body. and a second connection hole provided in the body and the support base to communicate the second seal chamber, the second center chamber, and the other end of the tube. Differential pressure measurement characterized by comprising a hole, and a sealed liquid sealed in each of two chambers consisting of a seal chamber, a communication hole, a center chamber, a connection hole, a tube, an internal chamber, and a measurement chamber. This is the configuration of the device.

In the above configuration, the measurement pressure applied to the seal diaphragm is passed through the connection hole to the first. Enter the second measurement room.

The differential pressure between the measured pressures is converted by the sensor element into an electrical signal corresponding to the differential pressure.

Next, when a high static pressure measurement pressure is applied, the first. Since high static pressure is applied to the second measurement chamber and static pressure is applied to the internal cavity, the differential pressure sensor is placed in static pressure, and the sensor element does not undergo any strain due to static pressure. , span fluctuations due to static pressure do not occur.

On the other hand, when excessive pressure is applied, if the pressure exceeds a certain level depending on the rigidity of the center die and aphram, the seal diaphragm contacts the pack-up nest and no more pressure is transmitted to the differential pressure sensor, and the differential pressure sensor protected.

Furthermore, even if the tightening force of the cover flange changes due to aging, etc., it does not directly act on the differential pressure sensor and the center diaphragm as an external force, and does not cause zero point or span shifts.

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

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

In the figure, structures with the same symbols as in FIG. 2 represent the same functions.

Hereinafter, only the differences from FIG. 2 will be explained.

31 and 32 are respectively provided on the outer surface of the body 1 and are connected to the body 1 and the first . This is a seal diaphragm that constitutes the second seal chambers 311 and 321.

A housing 7 is attached to the body 1 on one side.

A recess 71 is provided in the housing 7 and forms a chamber 72 with the body 1 .

Reference numeral 73 denotes a support base that is attached to the body 1 on one side, is placed in the recess 71 with a gap therebetween, and forms the recess 71, the first center chamber 731, and the internal chamber 732.

The internal chamber 732 contains the main body 42 and the first. Second measurement chamber 423
, 424 and a measuring diaphragm 422 which is a sensor element.
and a fixed type [425, 426 etc. differential pressure sensor 40]
is located.

733 is a ring-shaped groove provided on the peripheral surface of the support base 73.

A cylindrical center diaphragm 74 is provided to cover the groove 733 and forms a second center chamber 741 with the groove 733 .

A tube 75 is connected at one end to the differential pressure sensor 40 and to the support stand 73 to communicate with the first measurement chamber 423 so as to support the differential pressure sensor 40 in the internal chamber 732 with a gap therebetween.

Reference numeral 76 denotes a communication hole provided in the differential pressure sensor and communicating the second measurement chamber and the internal chamber.

A first connecting hole 77 is provided in the body 1 and communicates the first seal chamber with the first center chamber 731.

A second connecting hole 78 is provided in the body 1 and the support base 73 and communicates the second seal chamber 321, the second center chamber 741, and the other end of the chup 75.

54.55 are seal chambers 311, 321, communication hole 76, center chamber 731, 742, connection hole 77.78, tube 7
5. Filled liquid is sealed in two chambers each consisting of an internal chamber 732 and measurement chambers 423 and 424.

In the above configuration, when a differential pressure is applied to the seal diaphragm 31, the center diaphragm 74 deforms inward in a drum shape depending on its rigidity, and transmits the differential pressure to the differential pressure sensor 40 via the sealed liquid 54.

A displacement proportional to this differential pressure is detected as a change in capacitance between the measurement diaphragm 422 and the fixed electrodes 425, 426, and converted into an electrical signal.

In this case, the seal diaphragm 31 is deflected inward,
At the same time, the seal diaphragm 32 is deflected outward via the center diaphragm 74 by the volume moved by the same deflection.

When a differential pressure is applied to the seal diaphragm 32, the center diaphragm 74 deforms outward into a drum shape depending on its rigidity and transmits the differential pressure to the differential pressure sensor 40 via the sealed liquid 55. The displacement proportional to this differential pressure is measured by the measuring diaphragm 4.
22 and the fixed electrodes 425 and 426, which is detected as a change in capacitance and converted into an electrical signal.

In this case, the seal diaphragm 32 deflects inward,
At the same time, the seal diaphragm 31 is deflected outward via the center diaphragm 74 by the volume moved by the same deflection.

Next, when a high static pressure measurement pressure is applied, the first. Since high static pressure is applied to the second measurement chambers 423 and 424 and static pressure is applied to the internal chamber 732, the differential pressure sensor 40 is placed under static pressure, and the sensor element is subjected to strain caused by the static pressure. Since this does not occur, span fluctuations due to static pressure do not occur.

On the other hand, when excessive pressure is applied, if the pressure exceeds a certain level depending on the rigidity of the center diaphragm 74, the sill diaphragm 3
1, 32 contact the pack-up nests 312, 322 and do not transmit any more pressure to the differential pressure sensor 40, and the differential pressure sensor 40 is protected from excessive pressure.

Further, even if the tightening force of the cover flange 5 changes due to aging or the like, no external force is directly applied to the differential pressure sensor 40 and the center diaphragm 74, and no zero point or span shift occurs.

As a result, (1) Since the body l can be made into an integral structure, the rigidity is increased, and deformation due to tightening of the cover flange 5 is reduced, and changes in the neutral position and rigidity of the seal diaphragms 31 and 32 can be reduced, and the zero point , aging changes in span etc. can be reduced. (Bolt tightening is less affected by rippling due to changes in force over time.) (2) Since the center diaphragm 74 has a structure that is mechanically isolated from external forces, the tightening of the cover flange 5 is It is essentially not affected by changes over time, and changes over time in zero point, span, etc. can be reduced.

(3) One of the features of the three-chamber structure of the conventional example shown in Figure 2 is that the sealed liquid 53 around the outside of the differential pressure sensor 40, which is necessary to protect the sensor from static pressure, is used to transfer the differential pressure to the sensor element. It is not used for the purpose of communicating.

The sealed liquid 53 is a liquid that is unnecessary for measuring differential pressure.
Although there is an advantage in making these independent, there are disadvantages in that the structure is complicated and the outer diameters of the seal diaphragms 31 and 32 are restricted.

In addition, in the conventional example shown in FIG. 2, the annular diaphragm 33
, 34 and adopt a two-chamber structure, the amount of the sealed liquid 51, 52 will increase by the amount of the filled liquid 53 surrounding the differential pressure sensor, and the seal diaphragms 31, 32 and the center diaphragm 2. design becomes difficult. (In the overpressure protection system of the present invention, the smaller the amount of sealed liquid, the more advantageous the design can be.) In the present invention, the center chamber 21.2 of the conventional example shown in FIG.
Since a space corresponding to 2 is provided in the housing 4, the sealed liquid necessary for measuring the differential pressure and the sealed liquid surrounding the differential pressure sensor 40 can be used for both, even with a two-chamber structure. The amount of liquid to be filled can be reduced, an advantageous design can be achieved, and the structure can be simplified.

In the above-mentioned embodiment, the differential pressure sensor 40 is described as being of a capacitance type, but it is not limited to this, and may be of a semiconductor strain gauge type, for example, and in short, any sensor capable of detecting differential pressure may be used. Good.

Furthermore, if the shape of the outer circumferential side surface of the support base 73 and the shape of the inner circumferential side surface of the housing 7 are configured to be similar to the deformed shape of the center diaphragm 74, the amount of liquid in the enclosure 1i54.55 can be reduced, and the expansion of the enclosed liquid can be reduced. The occurrence of temperature errors due to etc. can be further reduced.

<Effects of the Invention> As explained above, the present invention includes a block-shaped body and a first body provided on the outer surface of the body.
．． a seal diaphragm constituting a second seal chamber; a pack-up nest provided on the body opposite to the seal diaphragm; a cover flange covering an outer surface of the body; and a housing having one side attached to the hotty. , four parts provided on the housing and forming the body and a chamber; a support base having one side attached to the body and disposed in the recess with a gap therebetween and forming the recess, the first center chamber, and an internal chamber; a ring-shaped groove provided on the peripheral surface of the support base; a cylindrical center diaphragm provided covering the groove and forming a second center chamber together with the groove; and a first center diaphragm provided in the inner cavity. a differential pressure sensor comprising a second measurement chamber and a sensor element; one end is connected to the differential pressure sensor so as to support the differential pressure sensor in the internal space with a gap therebetween; the other end is connected to the support base; A tube that is connected and communicates with the first measurement chamber, a communication hole provided in the differential pressure sensor that communicates the second measurement chamber and the internal chamber, and a communication hole provided in the body that communicates the first seal chamber and the inner chamber. a first connection hole that communicates with the first center chamber; a second connection hole that is provided in the body and the support base and communicates between the second seal chamber, the second center chamber, and the other end of the tube; A differential pressure measuring device characterized by comprising the seal chamber, a communication hole, a center chamber, a connection hole, a tube, and a liquid sealed in each of two chambers consisting of an internal chamber and a measurement chamber. Configured.

As a result, (1) Since the body can be made into an integral structure, machinability is improved, deformation due to tightening of the cover flange is reduced, and changes in the neutral position of the seal diaphragm and machinability are minimized, and zero point, span, etc. Changes over time can be reduced.

(Bolt tightening is less susceptible to loosening due to changes in force over time.) (2) Since the center diaphragm is mechanically isolated from external forces, tightening of the cover flange is less affected by changes in force over time. Essentially unaffected by changes, changes over time in zero point, span, etc. can be reduced.

(3) One of the features of the conventional three-chamber structure is that the sealed liquid around the outside of the differential pressure sensor, which is necessary to protect the sensor from static pressure, is not used for the purpose of transmitting the differential pressure to the sensor element. This is not the case. The sealed liquid is unnecessary for measuring differential pressure, and there are advantages to making it independent, but there are disadvantages such as a complicated structure and restrictions on the outer diameter of the seal diaphragm, etc. .

In addition, in the conventional example, the annular diaphragm is eliminated,
In the case of a two-chamber structure, the amount of the sealed liquid in the two chambers increases by the amount of the filled liquid surrounding the differential pressure sensor, making it difficult to design the seal diaphragm and center diaphragm. (In the overpressure protection system of the present invention, the smaller the amount of sealed liquid, the more advantageous the design can be.) In the present invention, a space corresponding to the center chamber of the conventional example is provided in the housing. Since the sealed liquid required to measure differential pressure and the sealed liquid surrounding the differential pressure sensor can be used together, even with a two-chamber structure, the amount of sealed liquid can be reduced and an advantageous design can be achieved. At the same time, the structure is also simplified.

Therefore, according to the present invention, it is possible to realize a differential pressure measuring device that can reduce zero point and span shifts, improve temperature characteristics, and achieve static pressure protection with a simple configuration.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the main part configuration of an embodiment of the present invention, Fig. 2 is an explanatory diagram of the configuration of a conventional example commonly used, Fig. 3 is an explanatory diagram of the parts of Fig. 2, and Fig. 4 FIG. 3 is an assembly diagram of the parts. DESCRIPTION OF SYMBOLS 1...Body, 31.32...Seal diaphragm, 311...First seal chamber, 321...Second seal chamber, 312.322...Pack up nest, 40.
... Differential pressure sensor, 42 ... Main body, 421 ... Chamber, 4
22... Measurement diaphragm, 423... First measurement chamber, 424... Second measurement chamber, 425, 426... Fixed electrode, 427° 428... Insulator, 5... Cover flange, 54.55... Enclosed liquid, 7... Housing, 71... Recess, 72... Chamber, 73... Support stand, 731... First center chamber, 732... Internal chamber,
733...Groove portion, 74...Center diaphragm, 7
41...Second center room, 75...Tube, 76
...Communication hole, 77...First connection hole, 78...Second
Connection hole. Figure 3 Figure 4

Claims (1)

[Claims] a block-shaped body; a seal diaphragm provided on the outer surface of the body and forming first and second seal chambers with the body; a backup nest provided in the body opposite to the seal diaphragm; a cover flange that covers an outer surface of the body; a housing having one side attached to the body; a recess provided in the housing and forming a chamber with the body; and a housing having one side attached to the body and maintaining a gap in the recess. A support base arranged to form the recess, the first center chamber, and an internal chamber; a ring-shaped groove provided on the circumferential surface of the support base; and a support base provided covering the groove and forming the groove and the second center chamber. a cylindrical center diaphragm, a differential pressure sensor provided in the internal cavity and comprising first and second measurement chambers and a sensor element, and supporting the differential pressure sensor in the internal cavity with a gap maintained therebetween; a tube having one end connected to the differential pressure sensor and the other end connected to the support base and communicating with the first measurement chamber; and a tube provided in the differential pressure sensor and connecting the second measurement chamber and the internal chamber. A communication hole that communicates with each other, a first connection hole that is provided in the body and that communicates the first seal chamber and the first center chamber, and a first connection hole that is provided in the body and the support base that communicates the second seal chamber and the first center chamber. 2, which communicates the center chamber with the other end of the tube.
a connection hole, the seal chamber, a communication hole, a center chamber, a connection hole,
1. A differential pressure measuring device comprising a tube and a liquid sealed in two chambers each consisting of an internal chamber and a measurement chamber.