JPH01240832A - differential pressure transmitter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a differential pressure transmitter in which a pressure transmitting fluid such as silicone oil is sealed within the meter.

[Prior Art] Generally, as a differential pressure transmitter, each process fluid pressure is applied to pressure receiving diaphragms on the high pressure side and the low pressure side, and the movement of the pressure transmission fluid due to this pressure is extracted as an electrical output by the distortion of the pressure sensor. something is known.

Conventionally, this type of differential pressure transmitter has been constructed as shown in FIG. To explain this based on the same figure, in the same figure, what is indicated by reference numeral 1 is a disc-shaped detector body consisting of a high-pressure side body 2 and a low-pressure side body 3, which are joined to each other. A barrier diaphragm 4 on the high-pressure side and a barrier diaphragm 5 on the low-pressure side each having a corrugated cross-section are attached to the end portions. This detector body 1 is formed with a backup surface 6.7 having a corrugated cross-section and facing both barrier diaphragms 4.5, and pressure transmission holes 8 that open in both backup surfaces 6.7.
．． 9 is provided. Each of the bodies 2 and 3 is provided with a liquid passage 10.11 that opens on the outer peripheral surface, and inside each of these liquid passages 10.11 there is a valve that suppresses sudden pressure fluctuations and pulsations of the process fluid. Stricter 12.1
3 is kept positive. Restrictors 14 and 15 have the same function as the restrictor 12.13, and each is held in its normal size inside the pressure transmission holes 8.9. Reference numeral 16 denotes a center diaphragm having a wave-shaped cross section and defining two chambers, a high-pressure side inner chamber 17 and a low-pressure side inner chamber 18, and is interposed between both bodies 2.3 of the detector body 1.

Reference numerals 19 and 20 denote two inner and outer cylinders with different diameters, which are fixed above the detection body 1. The inner cylinder 20 has a pressure sensor (not shown) made of, for example, a silicon diaphragm. Built-in. The liquid passages 10 and 11 are located between these two cylinders 19 and 20.
An annular passage 21 is formed which communicates with the liquid passage 11 on the low pressure side, and this annular passage 21 is connected to a negative side passage (not shown) of the pressure sensor (not shown).

Note that the high pressure side liquid passage 10 is connected to the other side passage (not shown) of the pressure sensor (not shown).

In the differential pressure transmitter configured in this way, when each process fluid is applied to the barrier diaphragm 4 on the high pressure side and the barrier diaphragm 5 on the low pressure side, each barrier diaphragm 4, 5 is depressed and the pressure transmitting fluid (Fig. (not shown) moves, a pressure sensor (not shown) detects the difference in the amount of movement, and transmits this as an electrical signal, which can be measured as a differential pressure.

[Problem to be solved by the invention]

By the way, in this type of differential pressure transmitter, when the pressure of each process fluid is applied, pressures F+ and Fz act in the body radial direction near the center diaphragm 16 as shown in FIG. (Because the center diaphragm 16 is asymmetrical in the left and right directions), there is a problem in that a zero point error occurs due to this shift l-ff1. In addition, the center diaphragm 16
The expansion in the radial direction is the compliance Φ of the center diaphragm 16. becomes smaller, ΔP, -ΔPXI
/(1+Z(ΦC/Φ, )), the received pressure value ΔP5 at the pressure sensor (not shown) changes, resulting in a span shift.

where ΔP and φ8 are the differential pressure of the process fluid and the compliance of the barrier diaphragm 4.5. Also,
Although the shift amount is corrected through characterization before the instrument is shipped, it is not possible to correct it sufficiently.

Currently, the instruments that can be used for correction are limited.

The present invention was made in view of these circumstances, and can prevent zero point errors and span shifts.
The present invention provides a differential pressure transmitter that can accurately measure pressure.

[Means to solve the problem]

The differential pressure transmitter according to the present invention includes a detector body that is connected to each other and has a liquid passageway that opens on the peripheral surface, and a high-pressure side interior chamber and a low-pressure side interior that are interposed between both bodies of the detector body. a center diaphragm defined in the detector body, an annular chamber extending around the center diaphragm is provided in the detector body, and the annular chamber communicates with one of the liquid passages. It is something that

[For production]

In the present invention, pressure acts on the peripheral wall within the annular chamber in a direction that offsets the pressure acting around the center diaphragm when pressure is applied to each process fluid.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, the structure etc. of this invention will be explained in detail by the Example shown in the figure.

FIG. 1 is a sectional view showing a differential pressure transmitter according to the present invention, and in the following figures, the same members as in FIGS. 4 and 5 are designated by the same reference numerals, and detailed explanations will be omitted. In the same figure, the detector body designated by numeral 31 is the body 3 on the high pressure side.
2 and a low-pressure side body 33, of which the low-pressure side body 33 is provided with an annular chamber 34 extending around the center diaphragm 16. The detector body 31 is provided with a communication hole 35 that communicates with the annular chamber 34 and the seventh passage 11 on the low pressure side of both liquid passages 10.11.

In the differential pressure transmitter configured in this manner, pressure acts on the peripheral wall 34a within the annular chamber 34 in a direction that cancels out the pressure acting around the center diaphragm 16 when pressure is applied to each process fluid. That is, when each process fluid is applied to the barrier diaphragm 4 on the high pressure side and the barrier diaphragm 5 on the low pressure side, this pressure F,, F,
As shown by the arrow in the figure, the high pressure side inner chamber 17. Low pressure side inner chamber 18
However, pressure F3 acts on the peripheral wall 34a in the annular chamber 34 in a direction that cancels out the pressure F, F2.
is in effect.

Therefore, in the present invention, it is possible to prevent fluctuations due to expansion of the center diaphragm 16 when pressure is applied to each process fluid, and therefore zero point errors and span shifts can be prevented from occurring.

In this embodiment, an example is shown in which a silicon diaphragm is used as a pressure sensor (not shown) to detect pressure changes, but the present invention is not limited to this.
In addition, there are other detection means that utilize capacitance changes and resistance changes, and these detection means can also be applied to various differential pressure transmitters as in the embodiments.

Further, in this embodiment, the case where the communication hole 35 is provided in the body 33 on the low pressure side is shown, but the present invention is not limited to this, and even if the body 32δ on the high pressure side is provided, the same effect as in the embodiment can be obtained. play.

Incidentally, in the present invention, the two bodies 32 and 33 are joined by EBW (Electric Beam) as shown in FIG.
Welding) allows the parts indicated by A and B to be performed simultaneously. After this, the pressure transmission fluid (
(not shown).

〔Effect of the invention〕

As explained above, according to the present invention, there is provided a detector body which is connected to each other and has a liquid passage opening on the circumferential surface, and a detector body which is interposed between both bodies of the detector body and has an inner chamber on the high pressure side and an inner chamber on the low pressure side. A center diaphragm defining a chamber is provided in the detector body, and an annular chamber extending around the center diaphragm is provided in the detector body, and this annular chamber is communicated with one of the liquid passages. , pressure acts on the peripheral wall within the annular chamber in a direction that offsets the pressure acting around the center diaphragm when the pressure of each process fluid is applied. Therefore, it is possible to prevent fluctuations due to expansion of the center diaphragm when pressure is applied to each process fluid, so it is possible to prevent zero point errors and span shifts from occurring.
Accurate pressure measurements can be made.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a differential pressure transmitter according to the present invention, FIG. 4 is a sectional view showing a conventional differential pressure transmitter, and FIG. 5 is a sectional view showing a state in which pressure is applied to a process fluid. 10.11...Liquid passage, 16...Center diaphragm, 17...High pressure side inner chamber, 18...Low pressure side inner chamber, 31...Detector body, 32... ...High pressure side body, 33...Low pressure side body, 34...
Annular chamber, 35... communicating hole.

Claims (1)

[Claims] A detector body consisting of a high-pressure side body and a low-pressure side body, each of which is joined to each other and has a liquid passage opening on the peripheral surface, and a high-pressure side inner chamber and a low-pressure side inner chamber interposed between both bodies of this detector body. a center diaphragm defining a chamber;
A differential pressure transmitter characterized in that an annular chamber extending around the center diaphragm is provided in the detector body, and the annular chamber communicates with one of the liquid passages.