JPS612033A - Differential pressure carrier - Google Patents

Abstract

PURPOSE:To prevent the initial bend due to the welding heat of a center diaphragm and the variation in the zero point output under high static pressure and to make the work easy by providing a projecting part having a rectangular section on the whole periphery of the inner face of the center part of a casing and by making it in symmetrical form. CONSTITUTION:A casing 21 is of cylindrical shape and a projecting part 37' having a rectangular section is projected over the whole periphery on the inner face of the central part in the axial direction thereof. The 1st disc 22 is inserted from the opening end of one part of the casing 21 and the stepped part is brought into contact with the side face of the projecting part 37' and on the opening end side, a diaphragm 25 for partitioning liquid is welded and fixed on the circumference. A center diaphragm 24 is also welded and fixed on the circumference of the smaller diameter part of a disc 22 being fit on the inner peripheral surface of the projecting part 37' and the 1st pressure chamber is formed by penetrating the space between the diaphragms 24, 25 with a through hole. The 2nd disc 22' is inserted from the opening end of the other part of the casing 21 and a diagram 25' is welded and fixed on the circumference on the end face of the opening end side. The end face of the opposite side is brought into contact with the side face of the projecting part 37' and the 2nd pressure chamber is formed by penetrating the space between the diaphragms 25, 24 with a through hole. The casing 21 is symmetrical and easy for working and yet of low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a differential pressure transmitter, and particularly to the structure of a casing equipped with an overpressure protection mechanism inside.

Technical background of the invention and its problems] FIG. 6 shows an example of the structure of a conventional differential pressure transmitter. (1).

(1) is the casing, (2) is the center diaphragm, (
3).

(No. 3 is a liquid diaphragm, (4L is a liquid separation diaphragm f3 when excessive differential pressure is applied), (3 is a liquid separation diaphragm seat for close contact, (5), (5 is a sealed pressure transmission medium, such as silicone oil, (6
).

(The 6th hole is a communication hole for transmitting pressure to the pressure sensitive element (7),
(8) is a lead for taking out the output from the pressure sensitive element (7), (9), (the target is a wetted flange for introducing the fluid to be measured;
(II.

(10mm is the O-ring, aυ is the center diaphragm (2mm)
) and casing (1) welded part, Mutsumi is casing (1)
Welded part between and (1'), 031. (No. 13 is one welded part of the diaphragm guiaphram (31, (3')) and the casing (1). Also, PH indicates the pressure to be detected on the high pressure side, and pL indicates the pressure to be detected on the low pressure side.

Now, on the high pressure side of this differential pressure transmitter, PH5 and PL (
Assuming that a pressure of It bends toward the low pressure side, and the pressure sensitive element (force is p, generates an output signal according to the differential pressure of -pL).

Furthermore, when a differential pressure exceeding the detection range is applied, the center diaphragm (2) further deflects toward the low pressure side, and the wetted diaphragm (3) also deflects toward the low pressure side by the volume moved at that time. (4) Sit down. Even if an even larger differential pressure is applied from this state, the liquid diaphragm (3) is prevented from moving any further, so no further differential pressure is transmitted to the pressure transmission medium (5), and as a result, The pressure sensitive element (7) is protected from excessive differential pressure. Then, when the excessive differential pressure is removed, the partition diaphragm (3) and the center diaphragm (2) return to their original positions. The same applies when excessive pressure is applied to the low pressure side (PH<PL).

In this type of overpressure protection mechanism, the pressure transmission medium (5), (5') sealed inside expands or contracts due to changes in ambient temperature, and the pressure transmission medium (5), (5'
) The expansion or contraction of the liquid diaphragm (3)
, (3') is absorbed. Hence the septum diaphragm (3).

As the clearance volume between (3 and diaphragm seats + 4) and (4) changes depending on the ambient temperature, the overpressure protection operating pressure value also changes. The upper limit must be a value that does not exceed the withstand pressure of the pressure sensitive element, and the lower limit must be a value that exceeds the upper limit of the measurement range of the differential pressure transmitter.Generally, the overpressure protection activation pressure value The fluctuation width increases in proportion to the amount of pressure transmission media (5), (5) sealed inside, so it is necessary in design to reduce the amount of pressure transmission media (t5), (5') as much as possible. Therefore, in order to reduce the gap between the center diaphragm (2) and the casing (1), the center diaphragm (2) is installed on the surface of the casing (1), (tQ) facing the center diaphragm (2).
) waveform (141) that matches the deflection shape of the curve.

By adding (14'), pressure transmission medium t51
, (5') weight loss has been achieved.

In the structure of this differential pressure transmitter, the center diaphragm (2)
is welded to the casing (1) in the thickness direction, but if the center diaphragm (2) is thick,
The center diaphragm (2) may bend due to the heat during welding. If the initial deflection of the center diaphragm (2) is large and the center diaphragm does not occupy the normal position,
Before the liquid diaphragm (3) or (3) seats on the liquid diaphragm seat (4) or (4'), the center diaphragm (2) hits the corrugation of the casing (1) or (1'). If the movement of the center diaphragm (2) is restricted in this way, the diaphragm (3) or (3) cannot move any further, and the excessive pressure is applied to the pressure transmission medium. (5) or (
The force is transmitted to the pressure sensitive element (7) through the pressure, making it impossible to protect the pressure sensitive element (7) from excessive differential pressure.

In addition, since the casing (1) has a U-shaped cross section including its centerline, when high static pressure is applied inside, the open side (left side in the figure) and the closed side (right side in the figure) of the casing (1) ), the deformation mode of the liquid-separating diaphragm (
3) Due to the difference in the tension between (high pressure side) and (3') (low pressure side) and the difference in volume of the chambers on the high pressure side and low pressure side, pressure cannot be sensed even when there is no differential pressure from the outside. Motoko (power,
A pressure difference occurs due to the difference in internal pressure between the high pressure side and the low pressure side, which causes the zero point output to deviate. Since such static pressure errors become more noticeable as the static pressure increases, the shape of the casing (1) as shown is not suitable for differential pressure measurement under high static pressure.

Furthermore, with the shape of this casing (1), the hole must be machined to a depth half of its axial dimension, which results in poor material usage efficiency and the formation of corrugations on the bottom surface of the hole. There is a drawback that processing to form (14') is difficult.

OBJECTS OF THE INVENTION The present invention aims to provide a differential pressure transmitter that eliminates various drawbacks such as initial deflection of the center diaphragm due to heat during welding, zero point output fluctuation under high static pressure, and poor workability. purpose.

[Summary of the invention]

The present invention provides a differential pressure transmitter in which the casing is formed into a cylindrical shape with a protrusion having a rectangular cross section protruding from the inner surface of the central part in the axial direction over the entire circumference, and the casing is inserted from one open end of the casing. and has a cylindrical shape with steps of different diameters that fit into the inner circumferential surface of the casing and the inner circumferential surface of the protrusion, the stepped portion abuts the side surface of the protrusion, and the peripheral edge of the end face located at the open end is welded and fixed to the casing. A liquid separation diaphragm formed on this end face which closes the liquid separation diaphragm seating surface with a gap is fixed at its peripheral edge by welding, and a corrugated surface formed on the end face of the small diameter portion that fits into the inner circumferential surface of the protrusion. A center diaphragm is sandwiched between a sealing disk having a corrugated surface facing the corrugated surface with a gap therebetween and fitted to the inner circumferential surface of the protrusion, and the peripheral edge thereof is fixed by welding to hold the center diaphragm. and the liquid separation diaphragm through a communication hole to form a first pressure chamber; and a cylindrical disk inserted from the other open end of the casing and fitted to the inner peripheral surface of the casing. The peripheral edge of the end face located at the open end is welded and fixed to the casing, and a liquid separation diaphragm that closes the liquid separation diaphragm seat formed on this end face with a gap is fixed by welding, and the peripheral edge is welded and fixed to the opposite side. The end surface abuts the side surface of the protrusion of the casing, and communicates between the liquid partition diaphragm and the center diaphragm of the first disk through a communication hole, thereby forming a second disk.
A differential pressure transmitter characterized by having a structure including a second disk forming a pressure chamber has been realized, and the intended purpose has been achieved.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a differential pressure transmitter according to an embodiment of the present invention.

The circle is a casing, which has a cylindrical shape, and has a symmetrical shape as shown in the figure, with a protrusion (37) having a rectangular cross section protruding from the inner surface of the central portion in the axial direction over the entire circumference.

A sensor housing portion □□□ is provided protruding from a part of the outer peripheral surface of the casing (21).

(2 is a gl disk, which is a stepped circle with different diameters that is inserted from one open end (left side in the figure) of the casing (21) and fits into the inner circumferential surface of the casing and the inner circumferential surface of the protrusion (9). The peripheral edge of the end face located at the open end is welded and fixed to the casing I21) as shown in the welded part (G), and the liquid separation diacrum seat surface (to) formed on this end face is A liquid-separating diaphragm closed with a gap is welded and fixed to the end face of the first disk (2) so that its peripheral edge is shown as a welded part (G).
The first disk (protrusion C37 of 221) has a corrugated surface (31) formed on the end surface of the small diameter portion fitted to the inner circumferential surface and a corrugated surface (39') opposite to this corrugated surface with a gap. The center diaphragm (2) is sandwiched between the sealing disc (the center diaphragm (2)) fitted to the inner circumferential surface of the protruding part C37), and its peripheral part is welded to the welding part G4.
) as shown by welding and holding, and connect the communication hole +
40 to form a first pressure chamber. The stepped portion of the first disk (221) is sealed by an O-ring G31 installed in an O-ring groove formed on the side surface of the protrusion (3) of the casing υ that is in contact with it.

(No. 22 is the second disk, which is inserted from the other open end of the casing Cυ (right side in the figure) into the casing 12)
It has a cylindrical shape that fits into the inner circumferential surface of the opening end, and the peripheral edge of the end face located at the open end is welded and fixed to the casing (21) as shown as a welded part (35mm), and is formed on this end face. A liquid separation diaphragm (25') which closes the liquid separation diaphragm seating surface (26') with a gap is fixed by welding to the end face of the second disk (22) at its periphery as shown as a welded part (36). The opposite end face protrusion (1
37). Then, connect the communication holes (4
A second pressure chamber is formed by communicating with each other through pressure. This second pressure chamber and the first pressure chamber inside the first disk are separated by an O-ring (c).

The structure of the other parts is the same as the conventional one.

(27) is a pressure transmitting medium sealed in the first and second pressure chambers, (27) is a pressure sensing element placed in the sensor housing (C), and is connected to the communication hole (28'). 1 and 2 pressure chambers. (31) is a lead for taking out the output of the pressure sensitive element to the outside, (31) is a wetted flange for introducing the pressure to be measured, C13 , (32')
is an o-ring. Further, pH is the pressure to be detected on the high pressure side, and PL is the pressure to be detected on the low pressure side.

Since the differential pressure detection operation and the overpressure protection mechanism of the differential pressure transmitter of the present invention and the embodiment configured as described above are exactly the same as those of the conventional example, the explanation will be omitted, and the effects will be explained. By making the shape of the casing Qυ bilaterally symmetrical, the deformation of the casing 0 when subjected to static pressure becomes symmetrical and the left and right sides are balanced, so the zero point output does not fluctuate even under high static pressure. In addition, in the conventional structure shown in Fig. 6, when excessive pressure is applied to the high pressure side, after the liquid separation diaphragm (3) is seated on the liquid separation diaphragm seat (4), the casing (1') As a result, the center diaphragm (2) receives a large surface pressure directly on the periphery, and if the breakage exceeds the yield point of the material, it becomes difficult to hold the center diaphragm (2) in place after the excessive pressure is removed. Therefore, the stiffness of the center diaphragm (2) changes, and the return (zero point hysteresis) after the center diaphragm (2) is deflected becomes worse. On the other hand, in the structure of the embodiment shown in FIG.
Since the center diaphragm (2) supports excessive pressure through the center diaphragm (2), the above-mentioned characteristics are not adversely affected.

Furthermore, in this structure, since the welding direction of the welding part (34) for the center diaphragm (two first discs (2)) is in the radial direction of the center diaphragm (to), the center Permanent deformation of the diaphragm (which appears as initial deflection of the center diaphragm) can be reduced. Also, since the center diaphragm 24) is welded before the first disk (24) is assembled into the casing (21), , the characteristics of the center diaphragm Q(a) after welding can be tested, and only those that meet the specifications can be installed on the casing cll).

In addition, since the casing υ has a cylindrical shape with both ends open, the general shape can be made by forging, making it easy to finish the inner surface by machining, and minimizing the amount of wasted material. Therefore, the manufacturing cost of the casing can be reduced.

In addition, the processing of the liquid diaphragm seat and the corrugated surface is also done in the first step.
Disc @ of the sealing disc, second disc (22')
Since each can be processed in its own state before being assembled, processing is facilitated.

Note that the present invention is not limited to the embodiments described above, and can be implemented with modifications as described below.

(a) As shown in Figure 2, the first disk (22
For sealing between the stepped portion 1 and the protrusion 07 of the casing (21) by an O-ring (c), an O-ring groove may be provided on the first disk Q side.

Cb] The seal between the first disc (the ridge and the casing (21) is made by welding the fitting part between the sealing disc 1231 and the inner peripheral surface of the protrusion c3 of the casing (21) as shown in Fig. 3). The seals between the casing (21) and the first and second disks (2a, (22')) may be welded together as shown at 421. will improve.

[c] In the modification shown in Fig. 4, the center diaphragm (24) is fixed with a corrugated disk (44) made of the same material as the center diaphragm by welding and then sandwiched between the corrugated disks (44). and the first disk at the welded part 143)
It was welded. Generally, stainless steel such as 5US316 is used as the material for the casing 121) and the first diagonal. Further, for the center diaphragm (2), a material with a high yield point, such as Ni-8PANC, is used. This is the center diaphragm (2
) becomes relatively large, and in 5US316, residual deformation remains beyond the yield point, causing the zero point as a differential pressure transmitter to fluctuate. However, sUs
The coefficient of linear expansion is considerably different between 316 and Ni-S PANCO, and the coefficient of linear expansion of Ni-8 PANCO is 1/2. Therefore, at high temperatures, the center diaphragm (koji) is pulled in the radial direction, and at low temperatures, it is compressed in the radial direction.Such a phenomenon not only changes the stiffness of the center diaphragm 12, but also causes buckling during compression. This adversely affects the performance of the differential pressure transmitter.The modification shown in FIG. 4 is effective in solving this problem.

Cd) The welding shown in Fig. 4 (instead of 43, weld the corrugated disc (44) and the first disc (221) as shown in Fig. 5).
and may be sealed using an O-ring +4<9.

This method can more easily absorb differences in linear expansion coefficients.

〔Effect of the invention〕

As described in detail above, according to the present invention, in a differential pressure transmitter, the casing has a cylindrical shape and a symmetrical shape in which a protrusion with a rectangular cross section protrudes from the inner surface of the central part in the axial direction over the entire circumference. By doing so, the deformation of the casing when subjected to static pressure becomes symmetrical, and the left and right sides are balanced, so there is no fluctuation in the zero point output even under high static pressure.

In addition, if excessive pressure is applied to the high pressure side, the disc of the vehicle 1 will receive the above excessive pressure after the liquid diaphragm is seated on the liquid diaphragm seat, but the first disk will move the stepped part of the casing. Due to the structure in which the protrusion is in contact with the side surface, the excessive pressure is supported by the protrusion of the casing, so a large surface pressure is not applied to the peripheral edge of the center diaphragm, and therefore the center diaphragm is not easily held down. This avoids adverse effects such as changes in the stiffness of the center diaphragm, and poor return after deflection of the center diaphragm. Furthermore, since the welding direction at the periphery of the center diaphragm is set in the radial direction of the center diaphragm, permanent deformation of the center diaphragm (initial deflection of the center diaphragm) due to thermal imbalance during welding is reduced, and the center diaphragm is placed in its normal position. This avoids the inconvenience of the center diaphragm coming into contact with the corrugated surface before the fluid diaphragm seats on the fluid diaphragm seat, and since the movement of the center diaphragm is restrained, the fluid diaphragm also does not touch the corrugated surface. This prevents the overpressure protection mechanism from failing in its function, where the overpressure protection mechanism becomes unable to move and the overpressure is transmitted to the pressure sensing element via the pressure transmission medium, causing the pressure sensing element to break. Additionally, since the center diaphragm is welded before assembling the first disk into the casing, it is possible to test the characteristics of the center diaphragm after welding, making it possible to install only those that meet specifications into the casing. As a result, the uniformity of the characteristics of the differential pressure transmitter can be improved. Furthermore, since the casing has a cylindrical shape with both ends open, it can be forged into the general shape, and the inner surface can be easily finished by machining, and the amount of wasted material is reduced. This makes it possible to reduce the manufacturing cost of the casing. Further, the liquid separation diaphragm seat and the corrugated surface can be easily processed since the first disk, the sealing disk, and the second disk can be processed individually before being assembled.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a differential pressure transmitter according to an embodiment of the present invention, FIGS. 2 to 5 are partial sectional views showing different modifications of the present invention, and FIG. 6 is a conventional differential pressure transmitter. FIG. 2 is a cross-sectional view showing the structure of a transmitter. 21... Casing 22... First disk 22'... Second disk 23... Sealing disk 2
4... Center diaphragm 25.25'... Separate diaphragm 26.26'... Separate diaphragm seat 27.27'.
...Pressure transmission medium 28.28'...Communication hole 29...
・Pressure sensitive element 31.31'...Liquid contact flange 3
2.32', 33... O-rings 34, 35, 35', 36, 36'... Welded portion 37... Protrusion 38... Sensor storage portion 39.39'... Corrugated surface 40 , 40'・
・・Communication hole 42.43・−・Welding part 44.45・
...Corrugated disc 46...Oring agent Patent attorney Inoue-Male Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 tD /'ko11/

Claims (5)

[Claims] (1) The center diaphragm connects the inside of the casing to the first
A fluid to be measured is introduced to the outside of a liquid-separating diaphragm that is separated into a pressure chamber and a second pressure chamber and is provided by closing both ends of the casing with a pressure-sensitive element that is provided in communication with both pressure chambers. A differential pressure transmitter that detects the differential pressure between the two pressure chambers via a pressure transmission medium sealed in the two pressure chambers,
The casing is cylindrical and has a protrusion having a rectangular cross section protruding from the inner surface of the central part in the axial direction over the entire circumference, and is inserted from one open end of the casing to form a protrusion on the inner surface of the casing. and having a cylindrical shape with different diameter steps that fit into the inner circumferential surface of the protrusion, the stepped portion abuts the side surface of the protrusion, and the peripheral edge of the end face located at the open end is welded and fixed to the casing, and is formed on this end face. A liquid separation diaphragm that closes the liquid separation diaphragm seating surface with a gap is fixed at its periphery by welding, and a gap is formed between the corrugated surface formed on the end surface of the small diameter portion that fits into the inner circumferential surface of the protrusion. A center diaphragm is sandwiched between a sealing disk having opposing corrugated surfaces and fitted to the inner circumferential surface of the protrusion, and the peripheral edge thereof is welded and fixed, and the center diaphragm and the liquid separation diaphragm are connected to each other. a first disk communicating through a communication hole to form a first pressure chamber; and a first disk having a cylindrical shape that is inserted from the other open end of the casing and fits into the inner peripheral surface of the casing, and the open end The peripheral edge of the end face located on the casing is welded and fixed to the casing, and the peripheral edge of the liquid separation diaphragm which closes the liquid separation diaphragm seat formed on this end face with a gap is welded and fixed, and the opposite end face is welded and fixed to the casing. The structure includes a second disk that abuts the side surface of the protrusion and communicates between the liquid separation diaphragm and the center diaphragm of the first disk through a communication hole to form a second pressure chamber. A differential pressure transmitter featuring: (2) A patent characterized in that the first pressure chamber and the second pressure chamber are isolated by attaching an O-ring to the contact area between the stepped portion of the first disk and the side surface of the protrusion of the casing. A differential pressure transmitter according to claim 1. (3) A patent characterized in that the first pressure chamber and the second pressure chamber are isolated by welding the fitting portion between the sealing disk of the first disk and the inner peripheral surface of the protrusion of the casing. Claim 1
Differential pressure transmitter described in section. (4) A center diaphragm is sandwiched between a pair of corrugated disks made of the same material as the center diaphragm, and the peripheral edges are welded and fixed, and the surface opposite to the waveform of one of the corrugated disks is 2. The differential pressure transmitter according to claim 1, wherein the outer peripheral edge is welded so as to come into contact with the end surface of the first disk. (5) A center diaphragm is sandwiched between a pair of corrugated disks made of the same material as the center diaphragm, and the peripheral edges are welded and fixed, and the surface opposite to the waveform of one of the corrugated disks is Claim 1, characterized in that the first pressure chamber and the second pressure chamber are isolated by making contact with the end surface of the first disk and attaching an O-ring to this contact portion. Differential pressure transmitter as described.