JPS5956136A - Differential pressure transmitter - Google Patents

Abstract

PURPOSE:To eliminate an error due to mechanical hysteresis, by specifying the movement of a moving element within a measurement range by a leaf spring and specifying the movement of respective materials in a body. CONSTITUTION:The center wall in the body 2 is divided into a high-pressure and a low-pressure part and a pressure receiving element 21 is disposed in a pressure receiving chamber 19 formed between them. The moving element 24 is fitted in the center part movable end of the pressure receiving element 21 freely movably in the axial direction of the center part through-hole 25 of the center wall 16, and leaf spring 26 and 27 are fixed to both side surfaces of the center wall 16 in an elasticity adjustable state; they are deformed elastically through the pressure receiving element 21 and moving element 24 when excessive pressure is applied, sitting pressure receiving diaphragms 4 and 5 on the side of the body 2.

Description

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

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

A differential pressure transmitter used for this type of pressure difference measurement applies each measurement pressure to pressure receiving diaphragms on the high pressure side and low pressure side, and the movement of the sealed liquid due to this pressure is detected by a semiconductor sensor installed by partitioning the sealed circuit. It is configured so that it is extracted as an optical output due to the distortion of the signal.

However, in this type of differential pressure transmitter, even if a pressure-receiving diaphragm with appropriate dimensions, strength, material, etc. is selected and used according to the measurement specifications of the process, it may sometimes receive excessive pressure. This overpressure can reach the semiconductor sensor and damage it, making subsequent measurements impossible. Therefore, various devices for protecting the sensor from this excessive pressure have been proposed and attached to the differential pressure transmitter.

However, in a differential pressure transmitter equipped with a conventional overpressure protection device, even under normal measurement pressure in which no overpressure occurs, the internal mechanism is displaced and the internal liquid moves, and the differential pressure remains as it is. Since the signal is not transmitted to the sensor, the transmission effect is low and the response is poor, as well as the measurement accuracy is reduced.

The invention was made in view of the above-mentioned points, and there is a pressure receiving element in which the central partition wall in the body is divided into two parts, a high pressure side and a low pressure side, and a pressure receiving element is disposed in a pressure receiving chamber formed between them. A movable element fixed to the movable end of the central part is engaged in a through hole in the central part of the medium-sized bulkhead so as to be movable in the axial direction, and leaf springs are fixed to both sides of the central bulkhead so that the elasticity can be adjusted freely to prevent excessive pressure. By configuring the pressure-receiving diaphragm to be elastically deformed via the pressure-receiving cable and the slider when application is applied, and the pressure-receiving diaphragm is seated on the body side, the movement of the internally sealed liquid within the measurement range is regulated to improve the conduction efficiency and measurement. The present invention provides a differential pressure transmitter with improved accuracy and responsiveness. Hereinafter, embodiments of the invention will be described in detail based on the drawings.

1 to 4 show an embodiment of the differential pressure transmitter according to the present invention, FIG. 1 is a sectional view thereof, FIG. 2 is a front view and side view of a leaf spring, and FIG. 3 is an example of applying excessive pressure. FIG. 4 is a sectional view of the differential pressure transmitter at the time, and is a green diagram showing the relationship between the pressure applied to the pressure receiving diaphragm and the pressure applied to the sensor. In the figure, a differential pressure transmitter 1 includes a body 2 integrally formed with a cylindrical part and a disc part that closes openings at both ends of the body 2, and a sealed sensor chamber 3 is integrally formed above the body 2. There is. A barrier diaphragm 4 on the high-pressure side and a barrier diaphragm 5 on the low-pressure side, which are formed in the shape of a disk with a corrugated cross section, are placed on the side surfaces of both side disk portions of the body 2, and between these and the side surfaces of the body 2, which have the same shape. The peripheral edge is fixed with a gap. 6 and T are covers that are respectively bolted to both sides of the body 2, and cover the pressure receiving chamber 8.6 and T between the barrier diaphragms 4 and 5.
Holes 10 and 10 are provided with holes to and ii opening toward 9.
．． 11 are communicated with the high pressure side and the low pressure side of the process fluid line, respectively. Furthermore, the gap behind the barrier diaphragms 4 and 5 and the inner chamber of the body 2 are communicated with each other by a liquid passage 12.13, and the inner chamber of the sensor chamber 3 and the inner chamber of the body 2 are also connected through a liquid passage. It is connected by 14.15.

In the inner chamber of the body 2, an inner chamber 17 on the high pressure side and an inner chamber 18 on the low pressure side are separated by a central partition 16 welded to the outer periphery of the body 2. It is divided into two parts, a high pressure side and a low pressure side, and a pressure receiving chamber 9 is formed between them. On the other hand, inside the sensor chamber 3, there is a terminal 2.
A semiconductor sensor 21 connected to 0 is mounted and fixed on a substrate 22, and the liquid passage 14, which opens to the high pressure side (inner chamber 17) in the body 2, opens to the high pressure side of the sensor 21.

Further, the liquid passage 15 that opens to the low pressure side internal chamber 18 in the body 2 is opened to the low pressure side of the sensor 21.

Reference numeral 23 designates a center diaphragm which is formed in the shape of a disk with a corrugated cross section and serves as a pressure receiving element that separates two chambers in the pressure receiving chamber 19, and whose fixed end on the periphery is fixed to the central partition wall 16. A mover 24 with a disc-shaped flange is identified at the center, which is the movable end. The shaft portion of the mover 24 has a communication hole 25 bored through the center of the central partition wall 16.
The end face of the shaft portion is set to be located on the same plane as the outer surface of the central partition wall 16 when no load is applied. Further, on both sides of the central partition wall 16, as shown in FIG.
The movable member 24 is fixed with a plurality of setscrews 28 so as to be able to adjust its elastic force, and its elasticity restricts the movement of the movable element 24 in the axial direction.

The gap between the barrier diaphragms 4, 5 and the body 2 of the differential pressure transmitter 1 configured in this way, the liquid passage? 2, 13, internal chambers 17, 1B, communication hole 25, two chambers of pressure receiving chamber 19, liquid passage 14, 15, and high pressure side and low pressure side of sensor 21 are filled with internal sealing liquid 29 such as silicone oil. . and the stiffness of the valley diaphragm 4°5.23 and the leaf spring 26.2
The spring pressure of No. 7 is set as follows. That is,′
Within the measurement pressure range of 1'9r rhinoceros, the center diaphragm 23
The plate springs 26 and 2γ are pressed against the central partition wall 16 to restrict the movement of the slider 24 in the axial direction 9, and a gap is formed between the barrier diaphragms 4 and 5 and the body 2. has been done. For example, if an excessive pressure higher than the short pressure is applied to the barrier diaphragm 4 on the high pressure side,
After the center diaphragm 23 is raised and the mover 24 pushes the leaf spring 27 on the low pressure side to elastically deform it, the barrier diaphragm 4 on the high pressure side is seated on the body 2 to stop the movement of the inner liquid 29.

Operation f of the differential pressure transmitter configured as above will be explained. In FIG. 1, a sinking pressure is applied to the high-pressure side diaphragm 4 that communicates with the high-pressure side of the process pipe through the hole 10,
Further, low pressure is applied to the diaphragm 5 on the low pressure side, which communicates with the low pressure side through the hole 11 . In this case, the leaf springs 26, 27 are pressed against the central partition wall 16, and the barrier diaphragm 4
, 5, the internal sealing liquid 29 moves toward the sensor 21 side. At this time, the pressure difference between the high-pressure side and the low-pressure side of the sensor 21 due to the movement of the sealing liquid 29 causes the sensor 21 to detect this pressure difference, convert it into an electrical signal, and transmit it. By inputting and calculating, it is possible to measure flow rate, liquid level, etc.

For example, if an excessive pressure higher than a predetermined pressure occurs on the high pressure side and is applied to the barrier diaphragm 4 on the high pressure side, the third
As shown in the figure, the internal sealing liquid 29 in the internal chamber 17 moves toward the pressure receiving chamber 19 side, bends the center diaphragm 23, and
4 moves in the axial direction to elastically deform the leaf spring 27 on the low pressure side, and the barrier diaphragm 4 on the high pressure side seats on the body 2 to stop the movement of the sealing liquid 29. Therefore, excessive pressure does not act on the sensor 21, and the sensor 21 can be kept in normal order. It operates in exactly the same way when excessive pressure occurs on the low pressure side.

FIG. 4 is a pressure relationship diagram in which the horizontal axis is the differential pressure ΔP on the barrier diaphragm, and the vertical axis is the working pressure P on the sensor. Point P1 is where excessive pressure is applied and the overpressure protection device is activated. Point P2 indicates the point at which the operation started, and point P2 indicates the point at which this operation ended.

As is clear from the figure, when excessive pressure is applied beyond the measurement range up to point P1, the pressure P on the sensor increases slightly, but it does not destroy the sensor, and after the protective device is activated, After the barrier diaphragms 4 and 5 are seated, this pressure will not rise. Even if the pressure changes within the measurement range, the plate will bounce26.27
Since the center diaphragm 23 and the mover 24 are stationary, the inner sealing liquid 29 only moves toward the sensor 21.
Errors due to mechanical hysteresis can be eliminated, a pressure that is correctly proportional to the measured pressure can be applied to the senna, and the responsiveness to changes in the measured differential pressure ΔP is extremely good.

Further, the leaf springs 26 and 27 are configured such that their spring pressure can be adjusted by rotating the upper screw 28 back and forth.
Adjustments are made for each transmitter.

This is because even though the spring pressure of the leaf spring 24 that restricts the movement of the slider 24 is determined according to the measurement range, there will be differences for each transmission due to manufacturing errors and variations in function of each component, so this must be adjusted. This adjustment allows for easy absorption of variations.

As is clear from the above explanation, according to the present invention, in a differential pressure transmitter, the central partition wall in the body is divided into two parts, a high pressure side and a low pressure side, and a pressure receiving element is arranged in a pressure receiving chamber formed between the high pressure side and the low pressure side. A movable element fixed to the movable end of the center of the pressure receiving element is engaged in a through hole in the center of the center partition so as to be movable in the axial direction, and plate springs are fixed to both sides of the center partition so as to be elastically adjustable. When an excessive pressure is applied, the pressure-receiving element and the slider are elastically deformed, and the pressure-receiving diaphragm is seated on the body side, so that the plate spring prevents the movement of the slider within the measurement range. to restrict the movement of each member within the body,
Since the internal liquid does not move in any direction other than the direction of the sensor, errors due to mechanical hysteresis are eliminated, allowing extremely accurate pressure measurement proportional to fluid pressure, which significantly improves measurement accuracy and also reduces changes in fluid pressure. The response to this is extremely good. Furthermore, since the spring pressure of the leaf spring can be adjusted, manufacturing process differences and function variations of parts can be easily absorbed, and the overpressure protection device is improved.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the differential pressure transmitter according to the present invention, FIG. 1 is a cross-sectional view thereof, FIG. 2 is a front view and side view of a leaf spring, and FIG. 3 is an example of a differential pressure transmitter according to the present invention. FIG. 4 is a cross-sectional view of the differential pressure transmitter at this time, and is a relationship diagram between the pressure applied to the pressure receiving diaphragm and the pressure acting on the sensor. 1...Differential pressure transmitter, 2...Body, 4゜5...
・・Barrier diaphragm, 14, 15・Φ・・Liquid passage,
16...Central h★wall, 17.18...Inner room, 1
9...Pressure chamber, 21φ...Sensor, 23 @I
I @ I+ center diaphragm, 24...Switcher, 25...Communication hole, 26.27...Plate spring, 2
8...Set screw. Patent applicant Yamatake Honeywell Co., Ltd. Agent
Masaki Yamakawa (and 1 other person)

Claims (1)

[Claims] A body having two liquid-filled chambers separated by a central partition wall and communicating through a liquid passage between a high pressure side and a low pressure side of the sensor, and pressure receiving diaphragms respectively disposed on both pressure receiving surfaces of this body. In the differential pressure transmitter, the central partition wall is divided into two parts, a high pressure side and a low pressure side, and a pressure receiving chamber is formed therebetween, and the fixed end of the peripheral part is fixed to the central partition side, and the movable end of the central part is fixed to the central partition wall side. A pressure-receiving element fixed to a moving element in a communication hole penetrating the central partition wall in the displacement direction is disposed in the pressure-receiving chamber, and within a normal measurement pressure range, movement of the moving element is elastically restricted to the pressure-receiving element. A leaf spring that is elastically deformed by being pushed by the slider when an excessive pressure is applied is fixed to both sides of the central partition wall so that the elastic force can be adjusted freely, and the elasticity of the pressure receiving diaphragm is applied to the body side when an excessive pressure is applied. A differential pressure transmitter characterized by being installed so that it is seated.