JPS6147370B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a differential pressure electric transmitter, which includes a pressure receiving part through which system pressures at two locations are transmitted via fluid, and a pressure receiving part that transmits pressure in the high pressure side and low pressure side to the pressure receiving part. The present invention relates to a differential pressure transmitter equipped with a differential pressure detection section that extracts a difference as an electrical signal.

In a differential pressure transmitter using a semiconductor differential pressure sensor, a plurality of chambers partitioned by diaphragms are provided in a pressure receiving section, and a differential pressure detecting section is provided at a location away from the pressure receiving section. Each pressure transmitted through the fluid from two locations in the fluid system deforms the diaphragm in each chamber. The chambers formed on the opposite side of the diaphragm from the pressure receiving side communicate with the differential pressure sensor and are independently sealed. Each of these sealed enclosures is filled with an enclosed liquid for pressure transmission. Therefore, a pressure based on the displacement of one diaphragm and a pressure based on the displacement of the other diaphragm are applied to the differential pressure sensor. As a result, the differential pressure sensor is displaced by an amount corresponding to the differential pressure of the applied filled liquid, that is, the differential pressure of the liquid introduced into the transmitter, and generates an electrical output signal in accordance with the displacement.

By the way, in conventional differential pressure transmitters, the central diaphragm of the central chamber is fixed to the main body of the pressure receiving part by welding. The area around the welded part of the diaphragm becomes annealed due to the influence of heat, so
The fulcrum of the movement of the diaphragm is away from the welding area, and the fulcrum changes depending on the welding conditions, so the operating characteristics when the diaphragm is displaced to one side,
There is a problem that the operating characteristics cannot be made the same when displaced to the other side, the zero point fluctuation becomes large, the linearity decreases, and stable and high measurement accuracy cannot be obtained. Furthermore, recently there has been a demand for measuring differential pressure under extremely high pressure, so considering the case where pressure is applied to only one side of the differential pressure sensor under high pressure, it is possible to achieve stable and high measurement as described above. Accuracy cannot be obtained.

The purpose of the invention is to solve the above-mentioned problems. That is, the object of the present invention is to provide a differential pressure transmitter which has a structure in which the fulcrum portion of the central diaphragm can be clearly defined, has no zero point fluctuation, and has excellent linearity.

In the present invention, the pressure receiving section is arranged in a first chamber having a first chamber.
It is composed of a main body part and a second main body part having a second chamber, each of the chambers is partitioned by a seal diaphragm, and the first main body part and the second main body part constitute a central chamber. The room is partitioned by a central diaphragm, the seal diaphragm and the central diaphragm are made of a corrosion-resistant metal material, and the area near the edge of the central diaphragm is
It is characterized by being configured to be fixed to the first body part by welding and pressed against it by a protrusion provided on the second body part.

Examples based on the present invention will be described below.

FIG. 1 is a sectional view showing the configuration of an embodiment of the present invention. The differential pressure transmitter shown in FIG. 1 includes a differential pressure detecting section 1 having a built-in semiconductor differential pressure sensor 10, a pressure receiving section 2 having a built-in high-pressure side seal diaphragm 20, a low-pressure side seal diaphragm 30, and a central diaphragm 40. We are prepared.

The semiconductor differential pressure sensor 10 is made of single crystal silicon formed on a disk, and a resistance is formed using a diffusion technique. The back side of the differential pressure sensor 10 has a circular concave portion protruding near the center, and the vicinity of the outer periphery of the back side is joined to the support body 12 via a thin glass. The differential pressure sensor 10 and support body 12 are housed in a seal fitting 55 and surrounded by a connecting fitting 50, a seal fitting 55, and a plate 57. Donut-shaped ceramic printed circuit board 15 wrapped around the outside of the differential pressure sensor 10
is arranged so as to be substantially flush with the differential pressure sensor 10, and a ceramic substrate protective cover 16 is provided to cover it. Differential pressure sensor 10
The upper bridge resistor and the substrate 15 are connected by a conductor, and further connected to a printed circuit 62 via a hermetically sealed lead wire 61. The printed circuit 62 is connected to a connector 65 via a compensation board 60 having a temperature compensation thermistor and the like. The connecting fitting 50 and the sealing fitting 55 are welded together, and the sealing fitting 55 and the plate 57
are also welded together. On the front side of the differential pressure sensor 10, the gap between the ceramic substrate 15 and the protective cover 16 communicates with the pressure guide path 52 of the connecting fitting 50, and these paths are filled with a sealed liquid. The back side of the differential pressure sensor 10 communicates with a pressure guiding path 54 through a hole formed in the support body 12, and these paths are filled with a sealed liquid. The periphery of the compensation board 60 is covered with a connector cover 63, and a seal fitting 55
A protective cover 56 is disposed around the outer periphery of. The differential pressure detection section 1 is attached to the amplification section main body case 66 with a fixing screw 7.
5, 76, etc. In this case, the O-ring 58 maintains airtightness.

The pressure receiving part 2 includes flanges 27 and 37, and a main body 2.
8 and 38 are attached to the gaskets 77, 78 using bolts 71, 73, etc. and tightening nuts 72, 74, etc.
are interposed and tightened to obtain pressure resistance and airtightness.
Each of the flanges 27 and 37 has a recess formed therein, and the recess of the flange 27 has an internal high-pressure fluid pressure port 24 opened therein, and the recess of the flange 37 has an internal low-pressure fluid pressure port 34 opened therein. There is. Each pressure port 2
4 and 34 communicate with different locations in the process, for example, upstream and downstream sides of the fluid, and the process fluid is introduced into each recess. flange 27,
37 and the bodies 28, 38 are made of stainless steel. Recesses are formed on the upper and lower surfaces of the cylindrical main body 28, respectively. One of the recesses has a corrugated bottom, and a high pressure side seal diaphragm 2 is formed with a corrugation corresponding to the corrugation of the bottom.
The vicinity of the edge of the diaphragm is joined to the main body 28 by electron beam welding so that the diaphragm 0 is disposed close to the bottom.

A first chamber is formed by the concave portion of the flange 27 and one concave portion of the main body 28, and this first chamber is connected to the high pressure side fluid chamber 21 and the high pressure side pressure receiving chamber 22 by the high pressure side seal diaphragm 20. be isolated. The bottom of the other concave portion of the main body 28 is also formed in a wave shape, and a central diaphragm 40 formed in a wave shape along the wave shape is disposed. The other recess and the central diaphragm 40 are arranged in close proximity to form an overload protection chamber 42 . The vicinity of the edge of the central diaphragm 40 is joined to the main body 28 by electron beam welding. The pressure guiding path 25 and the damper 29 communicate the high pressure side pressure receiving chamber 22 and the overload protection chamber 42 . Main body 28 and connecting fitting 5
0 and is welded together.

Recesses are also formed on the upper and lower surfaces of the disc-shaped main body 38, respectively. The bottom of one of the recesses is formed in a waveform that follows the waveform of the central diaphragm 40. The bottom of the other recess is also formed in a corrugated shape, and the corrugated low-pressure side seal diaphragm 30 is disposed adjacent to the bottom. The vicinity of the end edge of the low-pressure side seal diaphragm 30 is joined to the main body 38 by electron beam welding. A disc-shaped main body 38 is fitted within the main body 28 . As shown in FIG.
presses the inside of the welded joint of the central diaphragm 40 welded to the main body 28 with a high load force. A central chamber with a central diaphragm 40 is separated by the central diaphragm 40 into overload protection chambers 42 and 44. In addition, the flange 37
The second recess formed by the recess of the body 38 and the recess of the main body 38
The chamber is separated into a low pressure side fluid chamber 31 and a low pressure side pressure receiving chamber 32 by a low pressure side seal diaphragm 30. The pressure guiding path 35 communicates the low pressure side fluid chamber 31 and the low pressure side pressure receiving chamber 32.

The volume of the overload protection chambers 42 and 44 is equal to that of the pressure receiving chamber 22,
The volume is larger than 32. As a result, excessive pressure is applied to one seal diaphragm, and even if that seal diaphragm is seated on the main body, the central diaphragm 40 will not be seated. The overload protection chamber 42 is
Pressure path and connecting fittings 50 formed in the main body 28
It is connected to the surface side of the semiconductor sensor 10 via a pressure guiding path 52, and together with these pressure guiding path 25 and the high pressure side pressure receiving chamber 22, it forms a first sealed part. This independent first enclosure is filled with silicone oil, which is an incompressible liquid. Overload protection chamber 44
communicates with the back side of the differential pressure sensor 10 via the main body 38, the pressure path formed in the main body 28, and the pressure path 54 of the connecting fitting 50, and these, the pressure path 35, and the low pressure side pressure receiving chamber 32 constitutes a second enclosing part. This independent second enclosure is also filled with silicone oil.

In the differential pressure transmitter having such a configuration, the pressure of the process fluid taken out from the high pressure side of the orifice in the flow path of the system (not shown) is transferred to the pressure guiding port 24.
The pressure is transmitted to the high pressure side fluid chamber 21 and presses the seal diaphragm 20. When a pressure change occurs in this high-pressure fluid, the change is transmitted to one side of the central diaphragm 40 by the sealed liquid in the first sealed part, and is also transmitted to the differential pressure sensor 10 via the pressure guide path 52.
transmitted to the surface of At the same time, the pressure of the process fluid taken out from the low pressure side of the orifice is transmitted from the pressure guiding port 34 to the low pressure side fluid chamber 31 and presses the seal diaphragm 30. When pressure is generated in this low-pressure fluid, the change is transmitted to the other surface of the central diaphragm 40 by the sealed liquid in the second sealed part, and is also transmitted to the differential pressure sensor 10 via the pressure guide path 54.
is transmitted to the back side of

The presence of the central diaphragm 40 prevents the overload fluid pressure from being directly transmitted to the differential pressure sensor 10 when an overload is applied to either the high pressure side fluid chamber 21 or the low pressure side fluid chamber 31.

The seal diaphragms 20, 30 and the central diaphragm 40 are sized according to the operating pressure range of the differential pressure transmitter.

The central diaphragm 40 is joined to the main body 28 by electron beam welding, and is further attached to the pointed end 3 of the main body 38.
If an overload is applied to one of the fluid chambers by strongly pressing the inner periphery of the welding point with 9,
The zero point did not change before and after the overload was applied. Furthermore, we were able to significantly improve non-linearity. That is, the fulcrum of the movement of the central diaphragm 40 is not the welded part but the point 39 of the main body 38.
Therefore, there is no thermal effect during welding, and it is not affected by welding conditions. Therefore, when the central diaphragm 40 is displaced to one side and when it is displaced to the other side, the fulcrum of the movement of the central diaphragm 40 is fixed mechanically, so the operating characteristics can be matched. .

FIG. 3 is a diagram for explaining another embodiment of the present invention, and the difference from FIG. 1 is that a central diaphragm 40
is pressed by a wave ring 49 built into the main body 38. Wave ring 29 is welded to main body 38. According to this structure, the fulcrum portion of the central diaphragm 40 is always pressed by the wave ring 29 with a constant pressure. That is, the main body 28
When the main body 38 is fitted and welded, the load force applied to the main body 38 can be reduced, and the influence of welding conditions can be completely eliminated. Therefore, the motion fulcrum of the central diaphragm 40 is the same when it is displaced to one side and when it is displaced to the other side, so a differential pressure transmitter with the same characteristics in both directions can be obtained, without zero point fluctuation, and with non-linearity. Significant improvements can be made.

As explained above, according to the present invention, it is possible to obtain a differential pressure transmitter that is stable for a long time and has excellent measurement accuracy, so the effects are enormous.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the configuration of an embodiment of the present invention, FIG. 2 is a sectional view showing details of the main parts of FIG. 1,
FIG. 3 is a sectional view showing essential parts of another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Differential pressure detection part, 2... Pressure receiving part, 10... Semiconductor differential pressure sensor, 20, 30... Seal diaphragm, 21, 31... Fluid chamber, 22, 32... Pressure receiving chamber, 24, 34... ...Fluid pressure inlet, 27, 37...
...Flange, 28, 38... Main body, 39... Pointed head, 40... Central diaphragm, 49... Wave ring, 50... Connecting fitting, 52, 54... Pressure guiding path, 55... Seal fitting.

Claims (1)

[Claims] 1 Equipped with a pressure receiving section through which pressures at two locations in the system are transmitted via fluid, and a differential pressure detecting section having a differential pressure sensor for extracting the difference in pressure transmitted to the pressure receiving section as an electrical signal. In the differential pressure transmitter, the differential pressure section is composed of a first main body having a first chamber and a second main body having a second chamber, each of the chambers being partitioned by a seal diaphragm,
The first main body portion and the second main body portion constitute a central chamber, the central chamber is partitioned by a central diaphragm, the seal diaphragm and the central diaphragm are formed of a corrosion-resistant metal material, and the central chamber is partitioned by a central diaphragm. A differential pressure transmitter, characterized in that the vicinity of the edge of the diaphragm is fixed to the first main body part by welding, and is pressed against it by a protrusion provided on the second main body part.