JPH0943082A - Balanced differential pressure transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a change in zero point of an overload protecting diaphragm especially due to high pressure and a change in zero point due to deformation of a pressure receiving member. SOLUTION: Chambers 17, 18 for receiving pressure of measured fluid are formed of a seal diaphragm attaching hole of a single pressure receiving member 20 and plugs 32, 35, 36, and seal diaphragms 6, 7 are attached in parallel to both ends of the pressure receiving member. An overload protecting diaphragm 4 and a sensor assembly 2 are provided in a perpendicular direction to the seal diaphragms 6, 7, a first pressure receiving chamber 201, a first isolation chamber 203 and a semiconductor differential pressure sensor are conductive via conductive paths, and similarly, a second pressure receiving chamber 202, a second isolation chamber 204 and the semiconductor differential pressure sensor are conductive via conductive paths. In order to suppress deformation of the second isolation chamber, a sealing member of the second isolation chamber is made into a double structure comprising first and second fixing jigs 8, 28, and a third isolation chamber 206 is provided between them to lead a pressure of the same fluid to be measured as the second isolation chamber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential pressure transmitter, and in particular, by suppressing the deformation of an isolation chamber, the influence of static pressure when the pressure of a fluid to be measured is high is reduced and the differential pressure is accurately detected. Balance type differential pressure transmitter.

[0002]

2. Description of the Related Art A conventional differential pressure transmitter generally comprises a pressure receiving member composed of two parts, a main body H and a main body L, as described in JP-A-60-185131. H
The first seal diaphragm was fixed to one side of the above, and the center diaphragm that functions as an overload protection diaphragm was fixed to the other side by incorporating the sensor assembly. The second seal diaphragm is fixed to one surface of the body L, and the other surface is overlapped with the body H and the body L so as to press the center diaphragm of the body H, and the outer periphery is welded. Further, first and second pressure receiving chambers are formed by the first and second seal diaphragms on both sides of the pressure receiving member composed of the main bodies H and L, and the first and second seal diaphragms have the first and second pressure receiving chambers. Apply the fluid. Then, the main body H, the center diaphragm, and the main body L form first and second isolation chambers, and further, a conduction path connecting the first pressure receiving chamber and the first isolation chamber, a semiconductor of the first isolation chamber and the sensor assembly. A conduction path that connects the differential pressure sensor, a conduction path that connects the second pressure receiving chamber and the second isolation chamber, and a conduction path that connects the second isolation chamber and the semiconductor differential pressure sensor are provided.

Filling liquid is filled in the first pressure receiving chamber, the first isolation chamber, the semiconductor differential pressure sensor, and the inside of the communication path connecting them. Similarly, the second pressure receiving chamber, the second isolation chamber, the semiconductor differential pressure sensor, and the conductive path connecting them are filled with the filled liquid, and the pressure is transmitted to the front and back surfaces of the semiconductor differential pressure sensor.

Further, by sandwiching the main bodies H and L with two flanges from both sides and tightening and fixing them with bolts and nuts, the measurement fluid pressure receiving chamber is provided between the first seal diaphragm of the main body H and the flange, and the main body. It is formed between the second sealing diaphragm of L and the flange.

On the other hand, Japanese Patent Laid-Open No. 6-194247 discloses a method for improving the measurement accuracy as compared with the above-mentioned conventional differential pressure transmitter.
There is a differential pressure transmitter described in the publication. In this differential pressure transmitter, when the center diaphragm as the overload protection diaphragm is provided in the main body member, for example, in a direction perpendicular to the pressure receiving direction of the center diaphragm so as to be different from the pressure receiving direction of the first and second seal diaphragms. It is provided.
Further, since the pressure receiving chamber for the measuring fluid and the pressure receiving chamber for the filled liquid are formed in a single pressure receiving member, the flange and the bolt and nut for fastening the flange are not required.

[0006]

However, the above prior art has the following problems.

In the differential pressure transmitter disclosed in JP-A-60-185131, the first and second seal diaphragms are
Since the center diaphragm and the sensor assembly are arranged side by side on the same axis, the main body member can be used when joining the members that support the respective diaphragms and when pressure is applied to the member that supports the seal diaphragm from the measured fluid. Deformation of the center diaphragm causes distortion of the shape and position of the center diaphragm, resulting in a change in the zero point of the center diaphragm.

Further, the measurement fluid pressure receiving chamber has two main bodies H and L.
It is formed by sandwiching it from both sides with individual flanges, tightening and fixing it with bolts and nuts. However, since the tightening force of this flange presses the main body H and the main body L from both ends, when the static pressure of the measurement fluid is applied to the first and second measurement fluid pressure receiving chambers, the fastening force is It changes depending on the pressure, and the body member is deformed by the change in the tightening force at the time of this pressure load, and the deformation of the body member causes the movement of the enclosed liquid filled inside, which deforms the center diaphragm, The effect appeared as a change in the zero point of the center diaphragm, which hindered accurate differential pressure measurement.

In the differential pressure transmitter disclosed in JP-A-6-194247, the pressure receiving direction of the center diaphragm (overload protection diaphragm) is different from the pressure receiving direction of the first and second seal diaphragms as described above. Even if the seal diaphragm is joined to the pressure receiving member, the deformation or strain of the main body member generated at this time is not transmitted to the overload protection diaphragm, and the change of the zero point of the center diaphragm can be eliminated. . Also,
The amount of deformation of the center diaphragm when pressure is applied can also be reduced, and the zero point change at this time can also be reduced. Furthermore, all pressure receiving chambers are formed within a single pressure receiving member, eliminating the need for flanges, bolts and nuts.
Since there is no change in the tightening force when static pressure is applied to the measurement fluid pressure receiving chamber and there is no deformation of the pressure receiving member body, it is possible to eliminate the change in the zero point of the center diaphragm due to the change in the tightening force when a pressure is applied.

However, in the differential pressure transmitter disclosed in Japanese Patent Laid-Open No. 6-194247, when the pressure of the fluid to be measured is a high pressure, the sealed structure forming the second isolation chamber located on the atmosphere side of the center diaphragm. The member may be deformed by the high pressure, and when the sealing member is deformed, the operation fulcrum of the center diaphragm moves and the zero point of the center diaphragm changes, so that the differential pressure cannot be measured with high accuracy.

It is an object of the present invention to provide a balanced type differential pressure transmitter capable of measuring a differential pressure with high accuracy without the operating fulcrum of the center diaphragm moving even under a high pressure of the measuring fluid.

[0012]

In order to achieve the above object, the present invention employs the following constitution. That is, it is formed by the first diaphragm attached to the pressure receiving member, is formed by the first pressure receiving chamber in which the first detection fluid is sealed, and the second diaphragm attached to the pressure receiving member. A second pressure receiving chamber in which a detection fluid is sealed, a differential pressure detection sensor arranged in the pressure receiving member, and a first pressure sensor attached to the pressure receiving member in a direction different from the first and second diaphragms, for example, at a right angle. A first isolation chamber formed by three diaphragms and connected to the first pressure receiving chamber, a sealing member attached to the pressure receiving member so as to fix an outer peripheral portion of the third diaphragm, and the third diaphragm. And a second isolation chamber that is connected to the second pressure-receiving chamber and that applies a pressure of a first measurement fluid to the first diaphragm, The pressure of the second measurement fluid is applied to the ram to apply the pressure of the first and second isolation chambers that are in communication with the first and second pressure receiving chambers to the differential pressure detection sensor to detect the difference between the two pressures. In the differential pressure transmitter, the deformation preventing means for suppressing the deformation of the second isolation chamber due to the pressure of the second measurement fluid is provided.

Preferably, the deformation preventing means is means for suppressing deformation of the sealing member by the pressure of the second measuring fluid itself. In this case, preferably, the sealing member has a double structure in which first and second fixing fittings are overlapped with each other, and the deformation preventing means has the second measurement between the first and second fixing fittings. It is a means for guiding the pressure of fluid.

Also, preferably, the deformation preventing means is
It comprises a third isolation chamber formed between the first and second fixing fittings, and a pressure transmission means for guiding the pressure of the second measurement fluid to the third isolation chamber. In this case, preferably, the pressure transmitting means, a fourth diaphragm attached to the pressure receiving member, a third pressure receiving chamber formed by the fourth diaphragm, the third detection fluid is sealed, And a conduction path for guiding the pressure of the third pressure receiving chamber to the third isolation chamber, and the pressure of the second measurement fluid is applied to the fourth diaphragm. And, preferably, the differential pressure transmitter of the present invention is a measurement fluid pressure chamber provided in the pressure receiving member so that the second measurement fluid is guided and the pressure of the second measurement fluid is applied to the second diaphragm. Further, the fourth diaphragm of the pressure transmitting means is arranged so that the pressure of the second measurement fluid introduced into the measurement fluid pressure receiving chamber is applied.

[0015]

In the differential pressure transmitter of the present invention constructed as described above, basically, like the differential pressure transmitter disclosed in Japanese Patent Laid-Open No. 6-194247, a third diaphragm (center diaphragm or overload protection) is provided. The pressure receiving direction of the diaphragm)
Since it is provided in a direction different from the pressure receiving direction of the first and second diaphragms (seal diaphragm), even when the seal diaphragm is joined to the pressure receiving member, the strain generated at this time is not transmitted to the overload protection diaphragm,
The zero point change of the overload protection diaphragm can be eliminated. Further, the amount of deformation of the overload protection diaphragm when pressure is applied can be reduced, and the zero point change at this time can also be reduced. Furthermore, since all pressure receiving chambers are formed in the same pressure receiving member and flanges, bolts and nuts are not required, there is no change in the tightening force when static pressure is applied to the measurement fluid pressure receiving chamber, and deformation of the pressure receiving member body etc. Therefore, it is possible to eliminate the change of the zero point of the center diaphragm due to the change of the tightening force under the pressure load.

As a feature of the present invention, by providing a deformation preventing means for suppressing the deformation of the second isolation chamber due to the pressure of the second measurement fluid, the operating fulcrum of the overload protection diaphragm does not move and the overload is prevented. Zero change of protective diaphragm does not occur.

Here, by providing a means for suppressing the deformation of the sealing member by the pressure of the second measuring fluid itself as the deformation preventing means, the deformation of the second isolation chamber can be suppressed with a simple structure.

Further, in this case, the sealing member has a double structure in which the first and second fixing fittings are stacked, and the deformation preventing means is provided between the first and second fixing fittings so as to apply the pressure of the second measurement fluid. By constituting by the guiding means, and more specifically, a third isolation chamber formed between the first and second fixing fittings,
By configuring the third isolation chamber with pressure transmitting means for guiding the pressure of the second measurement fluid, the same pressure of the second measurement fluid is applied to both surfaces of the first fixing member, and the sealing member is deformed. The deformation of the (first fixing bracket) is suppressed.

Further, the pressure transmitting means includes a fourth diaphragm attached to the pressure receiving member, a third pressure receiving chamber formed by the fourth diaphragm and containing a third detection fluid, and a third pressure receiving means. The third isolation chamber is configured so that the pressure in the chamber is constituted by a conducting path for guiding the pressure to the third isolation chamber, and the pressure of the second measurement fluid is applied to the fourth diaphragm. Since the measurement fluid is not directly guided, the differential pressure can be measured even if the second measurement fluid is any fluid such as a corrosive fluid. Further, since the third pressure receiving chamber is formed in the same pressure receiving member as the one to which the sealing member is attached, it is possible to shorten the path for taking the measured fluid pressure into the sealing member having the double structure, which also has the effect of making it compact. .

Further, the pressure receiving member is provided with a measurement fluid pressure receiving chamber so as to apply the pressure of the second measurement fluid to the second diaphragm, and the fourth diaphragm of the pressure transmitting means is guided to the measurement fluid pressure receiving chamber. By arranging so that the pressures of the two measurement fluids are applied, one measurement fluid pressure receiving chamber is shared by the two diaphragms, and the structure is simplified.

In the present invention, by applying the same pressure inside the sealing member against the pressure in the third isolation chamber,
The differential pressure transmitter of the present invention is specifically referred to as a "balanced" differential pressure transmitter.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A balanced differential pressure transmitter according to an embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, a differential pressure transmitter according to the present embodiment includes, roughly speaking, a sensor assembly 2 having a pressure receiving member 20 that constitutes a transmitter main body, and a semiconductor differential pressure sensor 44 disposed in the pressure receiving member 20. ,
First and second measurement fluid pressure receiving chambers 17, 18 formed in the pressure receiving member 20 and into which the first and second measurement fluids are guided, and arranged in the first and second measurement fluid pressure receiving chambers 17, 18 And the first and second seal diaphragms 6, 7 to which the pressure of the second measurement fluid is applied, and the first and second seal diaphragms 6, 7 formed between the pressure receiving member 20 and the first and second seal diaphragms 6, 7. The second pressure receiving chambers 201 and 202, the overload protection diaphragm (center diaphragm) 4 whose outer peripheral portion is joined to the pressure receiving member 20, and the overload protection diaphragm 4 separate the first pressure receiving chamber 201 and the second pressure receiving chamber 201, respectively. , 20
2 is provided with first and second isolation chambers 203 and 204, the pressure of the first measurement fluid is applied to the first sealing diaphragm 6, and the second measurement fluid is applied to the second sealing diaphragm 7. Applying pressure to the first and second pressure receiving chambers 201,
First and second isolation chambers 203 and 204 that communicate with 202
Is applied to the semiconductor differential pressure sensor 44 of the sensor assembly 2 to detect the difference between the two pressures.

Further, the differential pressure transmitter of the present embodiment is provided with a third seal diaphragm 3 which is arranged as a fourth diaphragm in the second measuring fluid pressure receiving chamber 18 and to which the pressure of the second measuring fluid is applied. The pressure of the third pressure receiving chamber 205 formed by the third seal diaphragm 3 and the pressure of the third pressure receiving chamber 205 is guided, and the deformation of the second isolation chamber 204 is suppressed by the pressure of the second measurement fluid. And an isolation chamber 206 of

FIG. 2 shows the structure of the pressure receiving member 20 shown in FIG. The pressure receiving member 20 is composed of a single member,
Holes 21 and 22 for symmetrically attaching the first and second seal diaphragms 6 and 7 are provided at both ends of 0.
The bottom surfaces of the holes 21 and 22 are processed into the same shape as the first and second sealing diaphragms 6 and 7, and the holes 21 and 22 are formed.
At the inlet of the screw part 3 having a larger diameter than the first and second seal diaphragms 6 and 7 for fixing the plugs 35 and 36.
7, 38 are formed.

Further, the hole portion 30 for attaching the third seal diaphragm 3 in the direction perpendicular to the surfaces of the hole portions 21, 22 for attaching the first and second seal diaphragms 6, 7.
Is provided, and a screw portion 34 for fixing the plug 32 is formed at the entrance of the hole 30.

Further, a stepped hole portion 23 for accommodating the overload protection diaphragm 4 and the sensor assembly 2 is formed on the central axis of the pressure receiving member 20 at right angles to the first and second seal diaphragms 6, 7. It is provided in the direction. The small diameter side of the stepped hole 23 is provided with a hole 9 for mounting the amplifier 9A, and the large diameter side thereof is provided with a first fixing member 8 and a second fixing member 8 which constitute a sealing member for fixing the overload protection diaphragm 4. Fixing bracket 2
Holes 10 are provided for attaching 8. The third isolation chamber 206 is formed between the first fixing member 8 and the second fixing member 28.

The first pressure receiving chamber 201 and the first isolation chamber 20
3. The surface of the semiconductor differential pressure sensor 44 of the sensor assembly 2 (the lower surface as viewed in FIG. 1) is electrically connected to each other through the conductive paths 24, 61, 63, and the second pressure receiving chamber 202 and the second The isolation chamber 204 and the back surface of the sensor assembly 2 (upper surface in FIG. 1) are electrically connected to each other through the conductive paths 25, 26, 27, 60, 62 (see FIG. 4). In addition, the third pressure receiving chamber 205 and the third isolation chamber 206 are connected to each other through the communication paths 81, 82, 83, 8
Conduction is made via 4, 85 (see FIG. 4). here,
The conduction paths 24, 25, 26, 27 and the conduction path 82 are formed in the pressure receiving member 20, and the conduction path 82 connects the hole 30 and the hole 10. Further, the conduction path 60 is formed in the sensor assembly 2, the conduction path 61 is formed in the center fitting 5, and the conduction path 6 is formed.
2 is formed in the first fixing member 8, the conducting path 63 is formed in the center fitting 5, the conducting paths 81, 83 are formed in the plug 32, and the conducting paths 84, 85 are formed in the second fixing member 28. ing.

In the differential pressure transmitter of this embodiment, the first pressure receiving chamber 201, the second pressure receiving chamber 202, the third pressure receiving chamber 205,
The structures of the first isolation chamber 203, the second isolation chamber 204, and the third isolation chamber 206 will be described in more detail by referring to FIGS. 1 to 4 and explaining an assembly process of the differential pressure transmitter.

In the differential pressure transmitter of this embodiment, the first and second seal diaphragms 6 and 7 are incorporated from the holes 21 and 22 of the pressure receiving member 20, and the first and second seal diaphragms 6 and 7 are attached. The first and second pressure receiving chambers 201 and 202 are formed by welding so that the surfaces are parallel to each other. Similarly, the third seal diaphragm 3 is also incorporated and welded from the hole 30, and the third pressure receiving chamber 205 is formed by welding the end surface portion by screwing the plug 32. Here, the conducting path 83 for conducting the conducting path 81 and the conducting path 82 is formed as an annular groove.

Next, the plugs 35 and 36 are screwed into the screw holes of the pressure receiving member 20, and the end face portions thereof are welded and sealed to form the first and second measurement fluid pressure receiving chambers 17 and 18. The second measurement fluid pressure receiving chamber 18 is provided with a pressure guiding passage 80 for transmitting pressure to the third sealing diaphragm 3.

The sensor assembly 2 is inserted into the central stepped hole portion 23 of the pressure receiving member 20 in the direction of the larger diameter so that the conducting path 60 of the sensor assembly 2 and the conducting path 25 of the pressure receiving member 20 are electrically connected. Assembling and welding both ends of the sensor assembly 2.

After that, the center metal fitting 5 is placed at a position where the conduction path 61 of the center metal fitting 5 and the conduction portion 24 of the pressure receiving member 20 are electrically connected, and the surface of the overload protection diaphragm 4 which has been processed into the corrugated shape is overloaded. The protective diaphragm 4 is attached toward the protection diaphragm 4 side, and the excessive / improper protection diaphragm 4 is attached to the pressure receiving member 20.
To form a first isolation chamber 203. Conduction path 63
Is provided at the center of the center metal fitting 5 so as to transmit pressure from the overload protection diaphragm 4 to the semiconductor differential pressure sensor 44.

The first fixing member 8 is provided in the hole 10 on the large diameter side of the stepped hole portion 23 so that the conducting path 62 of the first fixing member 8 and the conducting path 26 of the pressure receiving member 20 are electrically connected to each other. Attach the surface of the load protection diaphragm 4 that has been machined in the same shape as the corrugated shape to the overload protection diaphragm 4 side.
The pressure receiving member 20 is sealed by welding to form the second isolation chamber 204. Then, the second fixing member 2 is attached to the threaded portion of the hole 10.
8 is screwed in and sealed by welding, and the third isolation chamber 206
To form

Here, as shown in FIG. 4, a diametrical groove 28a is formed on the end face of the second fixing member 28 on the first fixing member side.
The groove 28a and the end face of the first fixing member 8 form a third isolation chamber 206. The conducting path 84 is formed as an annular groove that conducts the conducting path 82 and the conducting path 85, and the end of the conducting path 85 on the opposite side of the conducting path 84 passes through the center of the second fixing member 28 in the axial direction. Groove 28a
It is open to.

Then, the first pressure receiving chamber 201, the first isolation chamber 203, the conducting paths 24, 61 and 63, and the sensor assembly 2
The space surrounded by the seal pin 51 of the sealing port 51 of the pressure receiving member 20 and the surface side of the semiconductor differential pressure sensor 44 is filled with the sealing liquid 15 as the first detection fluid, and similarly, the second pressure receiving chamber 202, Second isolation chamber 204, conduction paths 25, 26, 2
7, 60, 62, and the seal pin 5 at the liquid sealing port of the pressure receiving member 20 and the back surface side of the semiconductor differential pressure sensor 44 of the sensor assembly 2.
The enclosed liquid 16 is used as the second detection fluid in the space surrounded by 2 as well.
Is filled. Further, the space surrounded by the third pressure receiving chamber 205, the third isolation chamber 206, the conducting paths 81 to 85, and the seal pin 50 of the liquid sealing port of the stopper 32 is filled with the enclosed liquid 19 as the third detection fluid. There is.

FIG. 5 is a detailed view of the overload protection diaphragm 4, the pressure receiving member 20, and the first fixing member 8 of FIG. The overload protection diaphragm 4 is welded and joined to the pressure receiving member 20 at the outer peripheral portion, and the inside of the welded portion is brought into contact with and pressed by the first fixing metal fitting 8 to form the first fixing metal fitting 8
Are welded and sealed by electronic beam welding. Therefore, since the operating fulcrum of the overload protection diaphragm 4 is pressed firmly, there is no influence of distortion during assembly, and the operating fulcrum is always clarified.

Further, when pressure is applied, the second isolation chamber 204
At the opposite end surface (atmosphere side) of the second fixing member 28 and the second fixing member 28, a large differential pressure is generated, the first fixing member 8 is elastically deformed, and the deformation causes the enclosed liquid to move to change the zero point. there's a possibility that. However, in this embodiment, the second fixing member 2
The third isolation chamber 206 is formed between the second isolation chamber 206 and the second isolation chamber 204, and the same pressure as that of the second isolation chamber 204 is applied. Therefore, there is almost no deformation amount, and the operation fulcrum of the overload protection diaphragm 4 is also present. It doesn't move. Therefore, there is almost no change in the zero point when pressure is applied.

The sensor assembly 2 includes a hermetic seal pin 45 electrically connected to the semiconductor differential pressure sensor 44, and the FP is provided on the hermetic seal pin 45 on the atmospheric pressure open side.
Since C46 is soldered, it is not necessary to provide the pressure receiving member 20 with a hole for taking out a sensor signal, which is required in the conventional differential pressure transmitter.

The differential pressure detecting operation of the balanced differential pressure transmitter having such a structure will be described with reference to FIG. When the first pressure from the process fluid as the first measurement fluid is applied to the first seal diaphragm 6, the first seal diaphragm 6 is used to apply the first pressure to the enclosed liquid 15 in the first pressure receiving chamber 201 on the back side thereof. A first pressure of a measuring fluid is transmitted.
This first pressure is further transmitted to the first isolation chamber 203 formed between the overload protection diaphragm 4 and the center metal fitting 5 through the conductive metal paths 24 and 61, and further to the conductive metal path 63 of the center metal fitting 5. Differential pressure sensor 44 of the sensor assembly 2
Transmitted to the surface of. Also, when the second pressure from the process fluid as the second measurement fluid is applied to the second seal diaphragm 7, the second pressure receiving chamber 202 on the back side is also similarly passed through the second seal diaphragm 7. Filled liquid 1
A second pressure of the second measuring fluid is transmitted to the second measuring fluid 6, and the second pressure is formed between the overload protection diaphragm 4 and the first fixing member 8 through the passages 25, 26 and 27. While being transmitted to the second isolation chamber 204, it is also transmitted to the back surface of the semiconductor differential pressure sensor 44 of the sensor assembly 2 via the conduction path 60. Thus, the semiconductor differential pressure sensor 44 detects the first and second pressures of the first and second measurement fluids transmitted to the front surface and the back surface of the overload protection diaphragm 4, and the output of the semiconductor differential pressure sensor 44 is hermetic. It is taken out from the seal pin 45 to the atmosphere open side, and is fed through the FPC 46 to the amplifier 9
Is transmitted to A.

Then, in the present embodiment, the second pressure is further transmitted to the sealed liquid 19 in the third pressure receiving chamber 205 via the third seal diaphragm 3, and this pressure is applied to the conduction path 81.
Is transmitted to the third isolation chamber 206 via ~ 85. As a result, the same pressure is applied to the first fixing member 8 from both sides of the second isolation chamber 204 and the third isolation chamber 205, so that the first fixing member 8 is not deformed and the overload protection diaphragm 4 of the overload protection diaphragm 4 is not deformed. The fulcrum of movement does not change.

Since the pressure receiving chambers 17 and 18 for the measuring fluid and the pressure receiving chambers 201, 202 and 205 for the filled liquid are all formed in the pressure receiving member 20 which is a single member, as in the conventional example, particularly flanges and No need for bolts and nuts to tighten the flange. That is, except that the sealing diaphragms 15, 16, 19 are fixed by welding to form the pressure receiving chambers 17, 18 for measuring fluid and the pressure receiving chambers 201, 202, 205 for filled liquid, only plugs 32, 35, 36 are provided. It's done.

As described above, according to the differential pressure transmitter of this embodiment, the pressure receiving direction of the overload protection diaphragm 4 is arranged in a right angle direction different from the pressure receiving directions of the first and second seal diaphragms 6, 7. Thus, compared with the conventional example in which all the diaphragms are arranged on the same axis, the welding portion of the overload protection diaphragm 4 and the pressure receiving member 20 is joined to the pressure receiving member 20 with the first and second seal diaphragms 6, 7. Since it can be provided at a position where strain is not transmitted, distortion does not occur in the shape and position of the overload protection diaphragm 4 during the assembly of the differential pressure transmitter, and the zero point of the overload protection diaphragm 4 does not change. .

Further, by disposing the overload protection diaphragm 4 in the right angle direction, even if an excessive pressure is applied from the process fluid to the first and second measuring fluid pressure receiving chambers 17 and 18, the first and second The strain of the member generated in the vicinity of the seal diaphragms 6 and 7 is less likely to be transmitted as strain to the overload protection diaphragm 4, and the zero point change of the overload protection diaphragm 4 is also reduced.

Then, in this embodiment, the first fixing member 8
Can be eliminated by utilizing the pressure of the second measurement fluid, so that the change of the operating fulcrum of the overload protection diaphragm 4 can be eliminated especially when the second measurement fluid is a high pressure fluid. Therefore, the differential pressure can be accurately measured without changing the zero point of the overload protection diaphragm 4.

Further, according to the differential pressure transmitter of the present embodiment, all the pressure receiving chambers 17, 18, 201, 202, 205 are formed in the pressure receiving member 20, so that the pressure receiving member 20 is constructed as a single component. Yes, the pressure receiving chambers 17, 18, 201, 202,
No flanges, bolts, or nuts are needed to form 205. Therefore, the shape change of the pressure receiving member 20 due to the tightening of the bolts and nuts and the measurement fluid pressure receiving chambers 17, 18,
Since there is no deformation of the pressure receiving member when one-sided pressure or excessive static pressure is applied to 201, 202, 205, the zero point change and the fulcrum change of the overload protection diaphragm 4 are eliminated.
The differential pressure can be measured more accurately.

Further, since the third seal diaphragm 3 is provided and the pressure of the enclosed liquid transmitted to the third pressure receiving chamber 205 is transmitted to the third isolation chamber 206, the third isolation chamber 206 does not have any pressure. Since the second measuring fluid is not directly guided,
The differential pressure can be measured when the second measurement fluid is any fluid such as a corrosive fluid. Further, since the third pressure receiving chamber 205 is formed in the same pressure receiving member 20 to which the sealing member (first and second fixing fittings 8, 28) is attached,
Conducting path 8 for taking the measured fluid pressure into the third isolation chamber 206
The paths 1 to 85 can also be shortened, and the entire differential pressure transmitter can be made compact.

Furthermore, since the third seal diaphragm 3 is arranged so that the pressure of the second measuring fluid in the second measuring fluid pressure receiving chamber 18 is applied, one measuring fluid receiving chamber 18 has two diaphragms 3. , 7 is also shared, which has the effect of simplifying the structure.

Another embodiment of the present invention will be described with reference to FIG. The present embodiment is an example in which the third seal diaphragm 3 of FIG. 1 is eliminated.

In FIG. 6, the conducting path 80 is connected to the conducting path 90, and the second measurement fluid pressure receiving chamber 18 is connected to the conducting path 8.
It directly communicates with the third isolation chamber 206 via 0, 90 and the conducting paths 84, 85. This embodiment is applicable when the second measurement fluid is a fluid such as oil that is not corrosive.

According to this embodiment, the same effects as the previous embodiment can be obtained, and the structure is simple and the manufacturing cost is low.

[0051]

According to the differential pressure transmitter of the present invention, since the deformation of the isolation chamber due to the pressure of the fluid to be measured is suppressed, it is possible to eliminate the change of the zero point of the overload protection diaphragm at the time of pressure load. An accurate differential pressure can be detected even if the fluid has a high pressure.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a balanced differential pressure transmitter according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of a pressure receiving member of the differential pressure transmitter shown in FIG.

FIG. 3 is a detailed vertical sectional view of an overload protection diaphragm portion of the differential pressure transmitter shown in FIG.

FIG. 4 is a top view of the second fixing member shown in FIG.

5 is a detailed vertical sectional view of a mounting portion of the overload protection diaphragm shown in FIG.

FIG. 6 is a vertical sectional view of a balanced differential pressure transmitter according to another embodiment of the present invention.

[Explanation of symbols]

2 ... Sensor assembly 4 ... Overload protection diaphragm (third diaphragm) 5 ... Center metal fitting 3 ... Third seal diaphragm (fourth diaphragm) 6, 7 ... First and second seal diaphragms (first and second) 2nd diaphragm) 8 ... 1st fixing metal fitting 28 ... 2nd fixing metal fitting 9 ... Amplifier mounting hole 10 ... Fixing metal fitting mounting hole 15, 16, 19 ... Filled liquid 17, 18, 205 ... 1st-3rd Measuring fluid pressure receiving chamber 20 ... Pressure receiving member 21, 22, 30 ... Seal diaphragm mounting hole 23 ... Sensor assembly housing hole 24 to 27, 60 to 63, 80 to 85 ... Conducting path 32, 35, 36 ... Plug 34, 37, 38 ... Screw hole 44 ... Semiconductor differential pressure sensor 45 ... Hermetic seal pin 46 ... FPC 50, 51, 52 ... Seal pin 53, 54 ... Liquid sealing port 201 ... First pressure receiving chamber 202 ... Second pressure receiving chamber 205 ... third pressure receiving chamber 203 ... first isolation chamber 204 ... second isolation chamber 206 ... third isolation chamber

Claims (6)

[Claims] 1. A first pressure receiving chamber formed by a first diaphragm attached to a pressure receiving member, in which a first detection fluid is sealed, and a second diaphragm attached to the pressure receiving member, A second pressure receiving chamber in which a second detection fluid is sealed, a differential pressure detection sensor arranged in the pressure receiving member, and a pressure detecting member attached to the pressure receiving member so as to face different directions from the first and second diaphragms. A first isolation chamber formed by a third diaphragm and connected to the first pressure receiving chamber, a sealing member attached to the pressure receiving member so as to fix an outer peripheral portion of the third diaphragm, and the third isolation chamber. And a second isolation chamber which is formed by a diaphragm of, and is connected to the second pressure receiving chamber, and applies a pressure of a first measurement fluid to the first diaphragm,
Apply the pressure of the second measurement fluid to the second diaphragm to apply the pressure of the first and second isolation chambers that are in communication with the first and second pressure receiving chambers to the differential pressure detection sensor The differential pressure transmitter for detecting the difference between the pressure difference and the pressure difference between the second isolation chamber and the second isolation chamber. 2. The differential pressure transmitter according to claim 1, wherein the deformation preventing means is means for suppressing deformation of the sealing member by the pressure of the second measurement fluid itself. vessel. 3. The differential pressure transmitter according to claim 2, wherein the sealing member has a double structure in which first and second fixing fittings are stacked, and the deformation preventing means includes the first and second fixing members. A differential pressure transmitter, which is a means for guiding the pressure of the second measurement fluid between fixing fittings. 4. The differential pressure transmitter according to claim 3, wherein the deformation preventing means includes a third isolation chamber formed between the first and second fixing fittings, and the third isolation chamber. And a pressure transmission means for guiding the pressure of the second measurement fluid to the differential pressure transmitter. 5. The differential pressure transmitter according to claim 4, wherein the pressure transmitting means is formed by a fourth diaphragm attached to the pressure receiving member and the fourth diaphragm, and a third detection fluid is provided. The enclosed third pressure receiving chamber,
A differential pressure transmission characterized in that it has a conducting path for guiding the pressure of the third pressure receiving chamber to the third isolation chamber, and the pressure of the second measurement fluid is applied to the fourth diaphragm. vessel. 6. The differential pressure transmitter according to claim 5, wherein said second pressure-measuring fluid is introduced to said pressure-receiving member so as to apply the pressure of said second pressure-measuring fluid to said second diaphragm. A differential pressure, further comprising a fluid pressure receiving chamber, wherein the fourth diaphragm of the pressure transmitting means is arranged so that the pressure of the second measuring fluid introduced into the measuring fluid receiving chamber is applied. Transmitter.