JPS61155832A - Liquid sealed type differential pressure transmitter - Google Patents

Abstract

PURPOSE:To improve reliability by arranging a pressure receiving diaphragm, an overpressure preventing mechanism, and an annular diaphragm coaxially while aligning them to the center of a body. CONSTITUTION:When pressure PH to be measured becomes excessive, the pressure PH is impressed to the outside of a bellows 22 through the pressure receiving diaphragm 21a and a pressure transmission medium 28a. When this excessive pressure is received, the bellows 22 moves to right and a valve rod 24 and valve parts 23a and 23b also move to right reacting to the motion. Then, the valve part 23a contacts the valve seat 29 of the body 20 to inhibit the medium 28a from moving. Namely, the movement of the medium 28a is inhibited to stop subsequent pressure transmission and the excessive pressure is never transmitted to a pressure sensitive element part 27. Further, if the temperature varies while the movement of the medium 28a is inhibited, differential pressure is generated owing to the thermal expansion of the media 28a and 28b, but this differential pressure is absorbed by an annular diaphragm 30. Differential pressure generated by thermal expansion while over pressure is prevented is not supplied to the element part 27 either.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a liquid seal that receives two measured pressures through a pressure transmission medium, converts it into an electrical signal corresponding to the difference in flesh pressure, and outputs the electrical signal. Regarding differential pressure transmitters.

[Technical background of the invention and its problems]

A conventional liquid ring type differential pressure transmitter is configured as shown in FIGS. 3 and 4, for example.

Reference numeral 10 denotes a cylindrical body, and pressure receiving diaphragms 72 Ila and 72 lb for receiving different measured pressures PHe PL are attached to both open ends thereof so as to close the open ends. In addition, in the cylindrical part of this Dedy 10,
An overpressure prevention mechanism is disposed concentrically with the cylindrical portion.

This overpressure prevention mechanism includes a first bellows 12 arranged to divide the cylindrical portion of the geddy 10 into two, a pair of valve portions 13m and 13b that respond to the bellows 12, and the valve portions I Ja and I A valve rod 1 that connects Jb and a bellows 12 and is movably attached to the dedi 10.
It consists of 4.

Further, in the upper part of the body 10, for example, a semiconductor pressure-sensitive element section 15 for converting pressure into an electric signal is installed. The pressure-receiving diaphragm 11a is provided at the opposite end of the semiconductor pressure-sensitive element portion 15.

The pressure P Hr P L applied at 11b is supplied via pressure transmission media 16m and 16b. The pressure transmitting fMFJ6a, 16b is enclosed in the ZE 10 by the pressure receiving diaphragms 11*, 11b, and is divided by the first bellows 12, the pressure sensitive element 15, and the second bellows 1777.

This first bellows 12 moves when one of the measured pressures becomes an excessive pressure, and moves through the valve stem 14 to the valve portion 1.
3 & or jJb is brought into close contact with the valve seat portion 18 of the body 10 to prevent movement of the pressure transmission medium 16m and operate to prevent excessive pressure from being applied to the pressure sensitive element portion 15.

On the other hand, the second bellows 12 controls the pressure transmission medium 16m, 16b which is generated due to temperature change while the movement of the pressure transmission medium 16m, 16b is prevented by the first bellows 12.
It operates to absorb the differential pressure caused by the thermal expansion of 6b.

In this way, the first bellows 12 and the valve part 13*,
Pressure transmission medium 16*, 1 when excessive pressure is applied than 13bK
6b is prevented from moving, and the second bellows 17 absorbs the differential pressure generated due to thermal expansion when the application of excessive pressure is prevented, so that excessive pressure is not applied to the pressure sensitive element portion 15Vc. ing.

However, in the conventional example configured in this way, as shown in FIG.
The center ci of the first bellows 12, the center 02 of the first bellows 12, and the center C3 of the second bellows 17 are different from each other, which complicates the machining of the body 10. In particular, the valve parts IJa, 13b of the overpressure prevention mechanism part and the valve The alignment with the seat 18 becomes complicated. Also, the diameter of the male Dee 10 is 1. Second
Since the bellows 12 and 17 are arranged in tandem, there are problems such as being restricted by their diameters and not being able to be miniaturized.

[Purpose of the invention]

The present invention has been made to address these problems and provides a liquid ring type differential pressure transmitter that has a simple structure and can be downsized.

[Summary of the invention]

The present invention is arranged coaxially with a pressure receiving diaphragm, which is an overpressure prevention mechanism having a pressure absorber that responds to excessive pressure and a valve part, and is constructed so that the inner diameter thereof is larger than that of the pressure absorber. An annular diaphragm is disposed coaxially with the pressure receiving diaphragm to suppress the amount of differential pressure generated when transmission of excessive pressure is blocked by the overpressure prevention mechanism, and the overpressure prevention mechanism prevents transmission of excessive pressure. The annular diaphragm is configured to absorb differential pressure caused by thermal expansion when excessive pressure application is blocked. .

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

20 is cylindrical? The openings at both ends thereof are closed by pressure receiving diaphragms 21 and 21b. The pressure receiving diaphragms 2 J a and 21 b are arranged coaxially with the cylindrical portion of the dee 20 . Also, this is Dee 2
An overpressure prevention mechanism is coaxially arranged in the cylindrical portion of No. 0. This overpressure prevention mechanism includes a stress absorbing body that divides the cylindrical portion into two, such as a bellows 22, and a pair of valve portions 23*, 23bs and the valve portion 23a that respond to the bellows 22.

A valve rod 24 connecting JJb to the bellows 22Vc, and a valve portion 23m integrated by this valve rod 24.

23b and an elastic body 25 that attaches the bellows 22 to the body 20 so as to be movable in the axial direction of the cylindrical portion.

Further, a pressure sensitive element section 27 is installed in the upper part of the body 20, which converts pressure into an electrical signal and outputs it to the outside via a terminal 26. This pressure sensitive element part? 71C, one pressure to be measured P is the pressure receiving diaphragm 2 &, this pressure receiving diaphragm 21a, the bellows 22, and the pressure sensitive element portion 27.
Through the pressure transmission medium 28m sealed in the chamber formed by 1I11 on one side of the
However, the pressure transmitting medium 28b is sealed in a chamber formed by the pressure receiving diaphragm 21b, the pressure receiving membrane 421b, the bellows 22, and the other surface of the pressure sensitive element portion 27.
are supplied through the respective sources.

This pressure transmission medium 28a has a non-pressure knitting property.

28b is isolated from the annular diaphragm JOK.

This annular diaphragm 30 has an inner diameter larger than the outer diameter of the bellows 22, and has a larger inner diameter than the outer diameter of the bellows 22 and the pressure receiving diaphragm 21a.

It is arranged coaxially with 21b. This annular diaphragm 30 transmits the pressure medium 28 a e generated when the pressure medium 28 a is prevented from moving by the overpressure prevention mechanism.
This is to absorb the differential pressure caused by the thermal expansion of J 8 b.

With this structure, when the pressure to be measured PH becomes excessive, the measured pressure P is applied to the outside of the bellows 22 via the pressure receiving diaphragm 21a and the pressure transmission medium 281. Upon receiving this excessive pressure, the bellows 22 moves to the right in the figure, and in response to this movement, the valve stem 24 and the valve portion 23a.

23b also moves to the right in the figure. The one valve portion 23h is in close contact with the valve seat 29 of the body 2Q to prevent the pressure transmission medium 28a from moving.

That is, since the movement of the pressure transmission medium 28a is blocked, no pressure is transmitted thereafter, and excessive pressure is not transmitted to the pressure sensitive element portion 21. Furthermore, if a temperature change occurs while the movement of the pressure transmission medium 28a is blocked, a differential pressure will be generated due to thermal expansion of the pressure transmission media 211m and 211b, but this differential pressure will be absorbed by the annular diaphragm 30. Ru. Therefore, differential pressure generated due to thermal expansion during overpressure prevention is also not supplied to the pressure sensitive element section 21.

〔Effect of the invention〕

In the present invention, the pressure receiving diaphragm, the overpressure prevention mechanism, and the annular diaphragm are arranged on the same axis and aligned with the center of the mezzo-ee, so alignment is easy, and the machining of the mezzo-ee is also simple, and can be easily performed using an automatic machine. Processing is also possible, improving processing and assembly efficiency. In addition, since the annular bellows is configured to suppress the amount of differential pressure generated due to temperature changes, it is possible to have a larger effective area and reduce the amount of differential pressure generated compared to the conventional bellows. , reliability is improved, and conversely, if the function is equivalent to that of a conventional bellows, it is possible to use an annular diaphragm with a smaller diameter, resulting in smaller size.

[Brief explanation of drawings]

1 and 2 are for explaining one embodiment of the present invention, FIG. 1 is a partial top view, and FIG. 2 is an A-A in FIG. 1.
The sectional view, FIG. 3, and FIG. 4 are for explaining a conventional liquid ring type differential pressure transmitter. FIG. 3 is a partial sectional view, and FIG. 4 is a BB sectional view of FIG. 3. It is. 20...2D, 21g, 21b...Pressure receiving diaphragm, 22...Bellows, 23*, :13b...φ
Valve part, 27... Pressure sensing element part, 28a628b... Pressure transmission medium, 30... Annular diaphragm.

Claims (1)

[Claims] In a liquid ring differential pressure transmitter that supplies different pressures to be measured to a pressure sensing element section through a pressure receiving diaphragm and a pressure transmission medium, and converts the differential pressure between both pressures to be measured into an electrical signal and outputs it,
When excessive pressure is applied, an overpressure prevention mechanism that responds to this pressure and prevents the movement of the pressure transmission medium is disposed coaxially with the pressure receiving diaphragm, and also prevents heat of the pressure transmission medium due to temperature changes during overpressure prevention. A liquid ring type differential pressure transmitter, characterized in that an annular diaphragm that suppresses the amount of differential pressure generated due to expansion is arranged coaxially with the overpressure prevention mechanism and the pressure receiving diaphragm.