JPS5957132A - Diferential pressure transmitter - Google Patents

Abstract

PURPOSE:To protect a sensot from excessive pressure, by arranging a spacer for partitioning a body inner chamber into two chambers to mount the communication means of an inner sealing liquid in the chamber of a low pressure side and a spring member for energizing said spacer to a center diaphragm side. CONSTITUTION:A center diaphragm 29 is formed into a disc shape having a corrugated cross-sectional area and provided in a body chamber 28 to form two chambers, that is, a low pressure side inner chamber and a high pressure side inner chamber. In addition, a spacer 30 freely advancing and retracting to a far and near direction with respect to the center diaphragm 29 and a leaf spring 31 as a spring member for energizing the spacer 30 to the side of the center diaphragm 29 are arranged in the low pressure side inner chamber formed between the center diaphragm 29 and the inner wall surface of a back plate 22a. By this constitution, the center diaphragm 29 and the spacer 30 are moved to the low pressure side against the repelling force of the leaf spring 31 and a sensor can be protected from excessive pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a differential pressure transmitter 2 that measures a pressure difference between two points, which is a process variable.

For example, when trying to measure the flow rate of fluid in a pipe, it is possible to install an oriswiss plate in the pipe to reduce fluid resistance, measure the pressure difference between the upstream side and the downstream side, and calculate the flow rate based on a predetermined calculation formula. It is being done.

The differential pressure transmitter used to measure the square difference of this rod applies each measurement pressure to the pressure receiving diaphragm on the high pressure side and the low pressure side, and the movement of the sealed liquid due to this pressure is controlled by a semiconductor device installed by dividing the entire sealed circuit. It is configured to extract electrical output based on the distortion of the sensor.

However, in this type of differential pressure transmitter, the process? Even if a pressure-receiving diaphragm with appropriate dimensions, strength, materials, etc. according to the specified specifications is selected and used, it may sometimes be subjected to excessive pressure, and this overpressure may reach the semiconductor sensor and cause it to malfunction. Damage to the sensor may make subsequent measurements impossible. Therefore, various types of bindings 11 have been proposed to protect the sensor from this excessive pressure and are attached to the differential pressure transmitter. .

Fig. 1 is a sectional view of a conventional differential pressure signal equipped with this type of 1μ large pressure holding Hφ device, and this is shown in the same figure. A barrier diaphragm 2 on the high pressure side is formed in the shape of a corrugated disk on both sides of the body 1.
and barrier diaphragm 3 on the low pressure side are installed.
These two rear diaphragms 2 and 3 are bolted to the body 1, and high pressure and low pressure are applied to the fluid flowing in through the holes 5 and 6 between the cover 4 on both sides and the body 1, respectively. has been done.

On the other hand, in a sensor chamber in the sensor capsule 7 above the body 1, there is a half-body sensor 8 that is connected to a screw (not shown).
is held and arranged on the substrate 9, and this sensor 8
Liquid passages 10 and 11 extend toward the body 1 from the high pressure side, which is the lower side 1i11, and the low pressure side, which is the upper side. The reference numeral 12 designates a center diaphragm formed in the shape of a corrugated disk, and the inner chamber provided at the central joint of the half-split body 1 is divided into a high-pressure side inner chamber 13 and a low-pressure side inner chamber 14. The liquid passages 10 and 11 are respectively opened into internal chambers 13 and 14. t, each of the barrier diaphragms 2 and 3 and the body 1
The gap formed between the two and the inner chamber 13.14 communicate with each other through liquid passages 15.16. Then, from the gap between the barrier diaphragm 2.3 and the body 1, the liquid passage 15°16, the inner chambers 13, 14 and the liquid passage 1.
An internal sealing liquid 17 of silicone oil qi is sealed between the high pressure side and the low pressure side of the sensor 8 via 0 and 11.

In the differential pressure transmitter constructed as described above, when high pressure and low pressure from the process are respectively applied to the barrier diaphragms 2 and 3, the barrier diaphragms 2 and 3 are dented and the internal liquid 1T is compressed by the amount of compression. The differential pressure is measured by the sensor 8 detecting the difference in the amount of movement of the sealed liquid 11 due to the pressure difference between the two l111, and transmitting this as electric number 1i.11. Ru. In this case, the center diaphragm 12 is deformed due to the pressure difference on both sides, but does not come into contact with the walls of the inner chambers 13 and 14. Further, the barrier diaphragms 2 and 3 do not come into contact with the body 1 during normal differential pressure measurement. For example, when excessive pressure acts on the high pressure side, the barrier diaphragm 2 on the high pressure side deforms greatly and comes into full contact A1+ with the body 1, so that the pressure on the high pressure side is no longer transmitted to the inside. That is, by seating the barrier diaphragm 2, j
li maintains large pressure, J's work money.

In this type of differential pressure transmitter that is fully equipped with an overpressure protection device, even under the normal measurement pressure range where no overpressure is applied, the internal liquid 17 flows not only toward the sensor 8 but also toward the center diaphragm. It also moves in the direction of displacing 12,
Since the pressure applied to the barrier diaphragms 2 and 3 is not directly transmitted to the sensor, not only is the transmission efficiency low and response is poor, but also the hysteresis due to repeated displacement of the center diaphragm 12 is severe, resulting in a decrease in the measured degree of blueness. Met. In addition, in this glazed differential pressure transmitter, -
The breaking strength of the sensor is set to about 5 times the upper limit of the measurement range in response to changes in environmental temperature ranging from 50℃ to 120℃ and taking into account variations in manufacturing accuracy and damping constant. In order to increase the measurement range and increase the measurement accuracy, it is desirable to reduce the above ratio so that the upper limit of the measurement range approaches the breaking strength of the sensor.

The present invention has been made in view of the above points, and consists of dividing the inner chamber of the body into two chambers by a center diaphragm, and incorporating a spacer provided with a means for communicating the internal sealing fluid in the low-pressure side chamber, and a center diaphragm. A spring member is provided to urge the spacer to the side, and when the differential pressure is below a predetermined pressure, the spacer is brought into close contact with the center diaphragm, and when the differential pressure is above a predetermined pressure, the spring member is compressed, and when excessive pressure is applied, the pressure receiving diaphragm is seated on the body. When the differential pressure between the high-pressure side and the low-pressure side is below a predetermined value, the movement of the center diaphragm is restricted by a spacer springed by a spring member, thereby improving pressure transmission efficiency, responsiveness, and measurement. The present invention provides a differential pressure transmitter that expands the measurement range and improves measurement accuracy by making it possible to bring the upper limit of the measurement range close to the sensor breaking strength. Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 2 is a sectional view showing an embodiment of a differential pressure transmitter according to the present invention. In FIG. ,
Each back plate 22a is integrally formed with a low-pressure side back plate 22a (all circular recesses reaching the center in the thickness direction) and a high-pressure side back plate 22b fitted in the recess.

In the side pressure receiving concave surface of 22b, a low pressure side barrier diaphragm 23 and a high pressure side barrier diaphragm 24 formed in the shape of a corrugated disk have a gap 2 between them and the same shaped pressure receiving bottom surface.
5.0 and each back play whose peripheral part is fixed to the body 22 side except for 26) 22. Although not shown, covers similar to those shown in FIG. 1 are joined to the barrier diaphragms 23 and 22b.
A low pressure and a high pressure of the fluid flowing in from the hole in the cover are respectively applied. The gaps 25 and 26 are connected by a bypass 27 having apertures at both ends, and on this bypass 27, at the joint of the back plate 22a and 22b, there is a body interior chamber 28, which is mostly connected to the back plate.
22a side and a part of it is located on the 22b side.

The one designated by the reference numeral 29 is formed into a disk shape with a corrugated cross section, and has two inner chambers in the body inner chamber 28, an inner chamber on the low pressure side and an inner chamber on the high pressure side.
It is a center diaphragm that separates the chambers, and its peripheral edge is welded to a back plate 22b.The inner wall surface of the back plate 22b is formed in the same shape as this center diaphragm 29.The center diaphragm 29 and the back plate Inside the low-pressure side inner chamber formed between the inner wall surface of the center diaphragm 22a and the center diaphragm 29, there is a spacer 30 that can freely move forward and backward toward the center diaphragm 29, and a disc spring as a spring member that biases the center diaphragm 29 toward the center diaphragm 29. 31 are arranged. The spacer 30 is formed into a disk shape, and the side surface on the center diaphragm 29 side is formed in the same shape as the center diaphragm 29 so as to be in close contact with the center diaphragm 29. A liquid passage 30B extending in a cross shape is provided. ) Also, the disc spring 31 is formed into a low conical shape, and when the differential pressure from the high pressure side is less than a predetermined pressure, it overcomes it and brings the spacer 30 into close contact with the center diaphragm 29, and when the pressure is higher than the predetermined pressure, the spacer 30 closes. The spring pressure is set so that it is pressed and compressed by 30.

On the other hand, inside the sensor capsule 32 integrally joined to the body 22, a semiconductor sensor and a substrate, which are not shown but are indicated by reference numerals 8 and 9 in FIG. The high pressure side of the sensor is communicated with the high pressure side interior chamber of the body interior chamber 28 through the liquid passage 33.

In addition, the low pressure side of the sensor is connected to the body inner chamber 2 by the liquid passage 34.
It communicates with the low-pressure side interior chamber of No. 8. And gap 25°26 behind barrier diaphragm 23.24, bypass 2γ
, the body interior chamber 2B, and the liquid passages 33.34 are sealed with an inner sealing liquid 37 such as silicone oil injected from the liquid sealing hole 35.3 (3). A plurality of communication holes 3 serve as communication means for this internal sealing liquid 3T.
8 is drilled.

The operation of the differential pressure transmitter constructed as described above will be explained below.
When high pressure and low pressure from the process are respectively applied to the barrier diaphragms 23 and 24, the barrier diaphragms 2
3.24 is depressed and the internal liquid 37 moves by the amount of compression,
Respective pressures are applied to the high and low pressure sides of the sensor. The sensor detects the pressure difference between both sides and transmits it as an electric signal, thereby measuring the pressure difference. in this case,
The pressure from the process is transferred to the barrier diaphragm 2 on the high pressure side.
The pressure applied to the barrier diaphragm 2 on the low pressure side
In most cases, the pressure applied to No. 3 is also high, and this case will be explained first. When the differential pressure is O, the spacer 30 is bounced by the countersunk spring 31 and is in close contact with the center diaphragm 29, whereas the spacer is in close contact with the center diaphragm 29 through the enclosed liquid 37f and H on the high pressure side. When the pressure is applied, the spacer 30 and the center diaphragm 29 are kept in close contact with each other if this differential pressure is less than a predetermined pressure. Therefore, during this time, the inner sealing liquid 3T moves only toward the sensor, and a pressure proportional to the differential pressure is applied to the sensor. When the differential pressure from the process falls below a predetermined pressure, the center diaphragm 29 and the spacer 30 move toward the low pressure side against the elastic force of the disc spring 31, and this pressure causes excessive pressure before it destroys the sensor. In this case, the barrier diaphragm 24 on the high pressure side
is seated on the pressure receiving surface of the hack plate 22b, so no more pressure is transmitted to the sensor, and the sensor can be protected from excessive pressure.

Next, although it is rare, the pressure on the barrier diaphragm 23 on the low pressure side is equal to the pressure on the barrier diaphragm 24 on the high pressure side.
In some cases, this is also large, so this will be explained below. That is, when differential pressure is applied to the low pressure side, the sealing liquid 37 in the gap 25 communicates with the bypass 27) and moves through 3E1 between the center diaphragm 29 and the spacer 30, and the center diaphragm 29 moves to the high pressure side. Displace. In this case, the movement of the sealing liquid 3T toward the sensor is similar to that of the conventional device Q" shown in FIG.
j, and the transmission efficiency is not necessarily good, but there is no problem because the pressure on the low pressure side is rarely higher than the high pressure side. Then, when the differential pressure reaches a predetermined pressure that is short of destroying the sensor, the barrier diaphragm 23 on the low pressure side seats on the pressure receiving surface of the back 7" ray 22a, so that no pressure higher than this reaches the sensor. is not communicated to
The sensor can be protected from overpressure.

FIG. 3 is a sectional view showing another embodiment of the present invention. In this embodiment, a bellows 39 is provided in the space between the spacer 30 and the body 22, and its fixed end is fixed to the back plate 22b. However, since it is the same as the previous embodiment except that the movable end is fixed to the spacer 30, the same reference numerals are given and the explanation thereof will be omitted.

By doing this, the sealing liquid between the high pressure side and the low pressure side
37 movements can be sealed.

In addition, in each of the above embodiments, the spacer 30 and the disc spring 3
1, the inner chamber on the low-pressure side is larger than the inner chamber on the high-pressure side, and there is a difference in the amount of liquid in the compartments. Therefore, if the body 22 and the internal liquid 3T expand simultaneously due to a change in environmental temperature, the differential pressure transmitted to the F-sensor will increase due to the large difference in the coefficient of expansion between the metal and silicone oil and the difference in the amount of liquid in the compartment. Affect. Therefore, as another embodiment, if the spacer 30 is formed of a material with a low coefficient of thermal expansion such as ceramic or invar, the inner IHff in the low pressure side inner chamber
Even if l 37 expands greatly, this can be completely offset by the low expansion rate of the spacer 30, eliminating the difference with the i6 pressure side where liquid 1-11- is less, completely eliminating the influence on the amount of differential pressure transmitted to the sensor. be able to.

Further, in each of the above embodiments, an example was shown in which a cross-shaped liquid passage 30a k was provided as a communication means for the inner sealing liquid to separate the spacer 30 from the center diaphragm 29, but the spacer 30
If the spacer 30 is isolated from the center diaphragm 29 by performing plastic processing such as forming a large number of protrusions on the side surface using a punch-type protrusion forming process called star punching, the process for forming the liquid passage can be performed. This makes it easier to reduce processing costs.

Furthermore, in each of the above embodiments, the inner sealing liquid 3 provided in the spacer 30
Although the example in which the communication hole 38 is provided as the communication means of 7 is shown,
The spacer 30 may be formed of a porous sintered metal with air permeability, a cellular metal, or a paulownia material such as ceramic, which eliminates the need for hole drilling or curved surface processing, thereby reducing processing costs. Not only can the internal liquid flow be smoothed, but also the compatibility of the overpressure device can be improved.

As is clear from the above explanation, according to the present invention, in a differential pressure transmitter, the inner chamber of the body is partitioned into two chambers by a center diaphragm, and the lower pressure side chamber is provided with a spacer and a spacer provided with a means for communicating the internal sealing liquid. The spacer is placed in close contact with the center diaphragm when the differential pressure is below a predetermined pressure, and the spring member is compressed when the differential pressure is above the predetermined pressure. By configuring the sensor to be seated on the body, not only can the sensor be protected from excessive pressure, but when the differential pressure is less than a predetermined value, the movement of the center diaphragm is restricted by the spacer that is spring-loaded by the spring member. Since the pressure is directly transmitted to the sensor, the transmission efficiency can be improved and the hysteresis caused by the center diaphragm being stationary can be reduced.

Since there is no movement of the sealing liquid in directions other than the direction of the sensor, pressure response is extremely good and measurement accuracy is improved. Since the size can be easily adjusted by adjusting the pressure, it is possible to easily respond to all conditions. Furthermore, since the upper limit of the measurement range can be brought closer to the sensor's destructive strength pL, the measurement range can be expanded, and a measurement range with high sensor transmission efficiency can be used, improving measurement accuracy and measuring accuracy. is significantly improved.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional differential pressure transmitter in which an overpressure holding device a is separated by ψ1d, and Figs. 2 and 3 show an embodiment of the differential pressure transmitter according to the present invention. 3 is a cross-sectional view of a differential pressure transmitter as another embodiment of the present invention. 21.21A...Differential pressure transmitter, 22...Body, 23.24-...Φ barrier diamond 72mm, 25.2
6... Gap, 27... Bypass, 2811.
...Inner body chamber, 29-...Center diaphragm, 3
0...e spacer, 31 K...disc spring, 33, 34
・Deluxe...Liquid passage, 3T...Internal sealing liquid, 38...Communication hole. Patent applicant: Yamatake Honeywell Co., Ltd. Agent Masaki Yamakawa (and one other person) Figure 1 Figure 2

Claims (3)

[Claims] (1) A gold film is placed inside the body on the bypass that connects the gap between each pressure-receiving diaphragm on both sides of the body and the body at the center, and a liquid passage is provided between the high-pressure side and the low-pressure side of the sensor within this body interior. A center diaphragm is provided to separate two chambers which are connected to each other, and the lower pressure side of the two chambers is provided with communication means for internal sealing fluid, so that the outer periphery of the center diaphragm is provided under normal measurement pressure. A differential pressure transmitter characterized in that a spacer that is in close contact with a fixed part is disposed with a spring member interposed between the spacer and the wall surface of the body. (2) The differential pressure transmitter according to claim 1, wherein the spacer gold body 9 is also formed using a material with a small coefficient of thermal expansion. (3) A 4N differential pressure generator according to claim 1, characterized in that the spacer is formed of a liquid-permeable material as a communication means for the internal liquid provided in the spacer.