JPS60220838A - Differential pressure transmitter - Google Patents

Abstract

PURPOSE:To increase the size of a measuring lens and prevent destruction by varying the sectional area of the fixture part of a body which supports the top and reverse surfaces of a center diaphragm according to destruction critical pressure to a surface where the pressure transmission medium of a semiconductor sensor operates. CONSTITUTION:The sectional area of the fixation part of the body 31 which supports the top and reverse surfaces of the center diaphragm 42 is made different according to destruction critical pressure to each surface of the semiconductor sensor 39. Therefore, the center diaphragm 42 has different rigidity to pressure operating on each chamber to prevent large pressure from being applied to a surface of the semiconductor sensor 39 having large destruction critical pressure and large pressure from being applied to a surface having small destruction critical pressure. Therefore, the measurement range is increased as compared with such a conventional differential transmitter the rigidity of the center diaphragm is set corresponding to the surface with small destruction critical pressure, and the semiconductor sensor is prevented from being destroyed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a differential pressure transmitter used for industrial measurement.

[Prior art]

For example, when trying to measure the flow rate in a pipe in process control, etc., an orifice plate is installed inside the pipe to create fluid resistance, the pressure difference upstream and downstream of this resistance is measured, and the flow rate is derived based on a predetermined calculation formula. is being carried out. A differential pressure transmitter is used for this measurement, and conventionally, each pressure is applied to the pressure receiving diaphragm on the high pressure side and the low pressure side.
The structure is such that the movement of the pressure transmission medium due to this pressure is extracted as an electrical output by distortion of a semiconductor sensor provided by partitioning the enclosed circuit.

FIG. 1 is a sectional view showing a conventional differential pressure transmitter, in which a body 1 is formed by being divided into a high pressure body 1a and a low pressure side body 1b, and a barrier diaphragm on the high pressure side is formed in a corrugated cross section on both sides. 2 and a barrier diaphragm 3 on the low pressure side are fixed to each other. The high-pressure side body 1a has a deep fit 5 in order to secure a space for mounting the neck member 4.
is provided, and the low pressure side body 1b is provided in this fitting allowance 5.
are fitted, and both members 1a and lb are welded at A in the figure. The barrier diaphragms 2 and 3 have covers 7 on both sides fixed to the body l with through bolts 6.
A high pressure and a low pressure are applied by the fluid flowing in from the hole 8.9 between the body 1 and the body 1, respectively. Further, a sensor capsule 1'0 is provided above the body 1 via a neck member 4, and a sensor chamber 1' in this sensor capsule 10 is provided.
A semiconductor sensor 11 is disposed at 0a so as to be held on a sensor stand 12.

Reference numeral 13 denotes a center diaphragm having a wave-shaped cross section, the edge of which is fixed to the body 1 so as to define an inner chamber provided at the central joint of the body 1 into a high pressure side inner chamber 14 and a low pressure side inner chamber 15. ing. 16 is a high pressure side liquid passage for pressure transmission, and the high pressure side inner chamber 14. It communicates with the lower side of the semiconductor sensor 11 and is provided in the high-pressure side body la and the neck member 4.

17 is a low pressure side liquid passage having the same function as the high pressure side liquid passage 16, and is connected to the low pressure side inner chamber 15. It communicates with the upper side of the semiconductor sensor 11 and is provided in the low-pressure side body 1b, the high-pressure side body 1a, and the neck member 4. In addition, both the inner chambers 14
．． 15 and the gaps 18.19 formed between each barrier diaphragm 2, 3 and the body 1 are communicated by liquid passages 20.21, respectively. And the gap 18.19
From liquid passage 20.21. Inner chamber 14.15 and liquid passage 1
A liquid 22 such as silicone oil, which is a pressure transmission medium, is sealed between the lower side and the upper side of the semiconductor sensor 11 via 6°17.

By the way, since the semiconductor sensor 11 is generally manufactured by chemically etching or electrolytically etching one surface, the strength against the pressure acting on the etched surface is different from the strength against the pressure acting on the unetched surface. The critical pressure for failure on the exposed surface becomes smaller. For this reason, in the conventional differential pressure transmitter, in order to protect the semiconductor sensor 11, the rigidity of the center diaphragm 13 is set in accordance with the breaking critical pressure for the surface of the semiconductor sensor 11 where the strength is small.

However, if the rigidity of the center diaphragm 13 is set in this way, the container will elastically deform in response to the pressure applied from the high pressure side, resulting in a problem that the measurement range cannot be increased. On the other hand, if the rigidity of the center diaphragm 13 is increased in order to obtain a large measurement range, the pressure acting from the low-pressure side will lead to destruction.

[Summary of the invention]

The present invention has been made in view of the above circumstances, and includes a liquid junction passage filled with a pressure transmission medium between a chamber communicating with one surface of a semiconductor sensor and a chamber communicating with the other surface of the semiconductor sensor. By using an extremely simple configuration in which the cross-sectional area of the fixed portion of the body that supports the front and back surfaces of the center diaphragm that defines the center diaphragm is made different depending on the breaking critical pressure for each surface of the semiconductor sensor, it is possible to prevent the semiconductor sensor from being destroyed. The present invention provides a differential pressure transmitter that can increase the measurement range. Hereinafter, its configuration and the like will be explained in detail with reference to embodiments shown in the drawings.

τ Example] FIG. 2 is a sectional view of a body showing a differential pressure transmitter according to the present invention, and in the same figure, the reference numeral 31 indicates the body;
This body 31 includes a high pressure side body 31a and a low pressure side body 3.
1b, and the high-pressure side body 31a is fitted into the low-pressure side body 31b such that a space is formed between the high-pressure side body 31a and the low-pressure side body 31b. Reference numeral 32 denotes a communication hole that communicates between both end surfaces of the low-pressure side body 31b, and is bored through the center portion. A communication hole 33 is bored in the high-pressure side body 31a at a position opposite to the communication hole 32, which communicates between both end surfaces.

That is, the space formed between the high pressure side body 31a and the low pressure side body 31b, the communication hole 32, and the communication hole 33
Therefore, there is a liquid junction passage 34 opened at both ends in the body 31.
is formed.

On both sides of the body 31, a pair of barrier diaphragms 35, 36 on the high pressure side and the low pressure side are formed in a corrugated cross section and seal a sealed liquid 37 such as silicone oil as a pressure transmission medium in the liquid junction path 34. It is fixed. 38.38
is a back-up surface provided on the end surface of the body 31 facing these barrier diaphragms 35, 36, and is formed in a wave shape so that the barrier diaphragms 35, 36 can be brought into close contact with each other;
This prevents the barrier diaphragms 35, 36 from being damaged.

A cover (not shown) is attached to the outside of the barrier diaphragm 35, 36 for introducing pressure from the high pressure side and the low pressure side. Although not shown, a sensor capsule is provided above the body 31 via a neck member, similar to the conventional one, and inside this sensor capsule, a semiconductor sensor 39 shown by a chain line is held on a sensor stand. It is located in 40 and 41 are liquid passages that are bored in the body 31 and communicate the liquid junction passage 34 with one and the other surfaces of the semiconductor sensor 39.

Reference numeral 42 denotes a center diaphragm having a corrugated cross section whose edges are fixed to the low-pressure side body 31b by welding or the like. The semiconductor sensor 39 is divided into a chamber that communicates with the upper side, and a chamber that communicates with the lower side, which is the other surface of the semiconductor sensor 39. The center diaphragm 42 is configured to elastically deform when a predetermined pressure is applied to protect the semiconductor sensor 39 from overpressure.

43 is a fixed part provided on the high-pressure side body 31H that supports the surface of the center diaphragm 42, and 44 is a fixed part provided on the low-pressure side body 31b that supports the back surface of the center diaphragm 42. The cross-sectional area of the semiconductor sensor 39 varies depending on the critical breaking pressure on the surface of the semiconductor sensor 39 on which the sealed liquid 37 acts.

In other words, in order to protect the semiconductor sensor 39, the inner diameters φAt+ φA□ of the fixing parts 43, 44 are set to be different, and the diameter of the elastically deformable portion of the center diaphragm 42 is made smaller on the high pressure side and smaller on the low pressure side. It is changed so that it becomes larger towards the side.

Here, if the pressure at which the mechanism for protecting the semiconductor sensor 39 as described above operates is P, then the inner diameters φAL, φA
Setting of H is performed based on the following formula.

P=V@/Φ However, vo: Amount of liquid sealed under the barrier diaphragm Φ:
(Volume Change/Pressure) Coefficient (Compliance) In this equation, compliance Φ is proportional to the support diameter of the center diaphragm 42, that is, the inner diameters φAt and φAH of the fixing portion 43.44 that support the center diaphragm 42 to the 6th power, so for example, , the ratio of the inner diameters is φAL :φ
If A11 = 1:2'', then the ratio of compliance Φ when pressure is applied from the high pressure side to when pressure is applied from the low pressure side is 1:2, and the ratio of pressures at which overpressure protection operates is 2. :1. Such a pressure ratio is set according to the breaking critical pressure for the upper and lower surfaces of the semiconductor sensor 39.

In the differential pressure transmitter configured in this way, when pressure is applied from the high pressure side, the center diaphragm 42 is supported on the back side by the fixing part 44 provided on the low pressure side body 31b. The sealed liquid 37 inside the high-pressure side barrier diaphragm 35 moves into the space within the body 31, and the pressure acting on the barrier diaphragm 35 is transmitted to the semiconductor sensor 39 by the sealed liquid 37. Ru. On the other hand, when pressure is applied from the low pressure side, since the surface of the center diaphragm 42 is supported by a fixed part 43 provided on the high pressure side body 31a, the center diaphragm 42 moves in proportion to the pressure using this fixed part 43 as a fulcrum. The sealed liquid 37 inside the low-pressure side barrier diaphragm 36 moves into the space within the body 31, and the pressure acting on this barrier diaphragm 36 is transmitted to the semiconductor sensor 39 by the sealed liquid 37. As a result, strain occurs in the semiconductor sensor 39 due to the pressure difference between the high pressure side and the low pressure side, and the differential pressure is measured.

At this time, since the diameters of the elastically deformable portions of the center diaphragm 42 are different, the center diaphragm 42 has greater rigidity against pressure applied from the high pressure side than against pressure applied from the low pressure side. Therefore, the pressure on the high pressure side is On the other hand, at pressure PI, the sealed liquid 37 moves by the amount V0 of sealed liquid inside the barrier diaphragm, and the barrier diaphragm 35 moves to the back-up surface 38.
Overpressure protection of the single conductor sensor 39 is performed by contacting the single conductor sensor 39. Similarly, in response to pressure from the low pressure side, the barrier diaphragm 36 comes into contact with the back-up surface 38 at a pressure P2 smaller than the pressure P1. As a result, the relationship between the pressure P transmitted to the semiconductor sensor 39 and the differential pressure p acting on the differential pressure transmitter is shown in FIG. 4 with the high pressure side being the positive side and the low pressure side being the negative side. Alternatively, a differential pressure of p2 or less is prevented from being transmitted to the semiconductor sensor 39.

Therefore, the center diaphragm 42 has a large rigidity against the pressure acting on the high pressure side communicated with the upper side of the semiconductor sensor 39 with a large critical pressure for failure, and is communicated with the lower side of the semiconductor sensor 39 with a low critical pressure of failure. It has a small rigidity on the low pressure side. Therefore, a large pressure can be applied to the high pressure side of the semiconductor sensor 39, and large pressure can be prevented from being transmitted to the semiconductor sensor 39 on the low pressure side where the critical pressure for destruction is small.
Can be overpressure protected.

〔Effect of the invention〕

As explained above, according to the present invention, the body supporting the front and back surfaces of the center diaphragm defines the liquid junction path into a chamber communicating with one surface of the semiconductor sensor and a chamber communicating with the other surface. Since the cross-sectional area of the fixing part is made different depending on the critical pressure for failure on each side of the semiconductor sensor, the center diaphragm has different stiffness against the pressure acting on each chamber, which prevents the failure of the semiconductor sensor. A large pressure can be applied to a surface with a large critical pressure, and a large pressure can be prevented from acting on a surface with a small critical pressure for destruction.

Therefore, compared to conventional differential pressure transmitters in which the rigidity of the center diaphragm is set to correspond to a surface with a small critical pressure for destruction, it is possible to increase the measurement range and prevent damage to the semiconductor sensor. effective.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a conventional differential pressure transmitter, Fig. 2 is a sectional view of a body showing a differential pressure transmitter according to the present invention, and Fig. 3 is a sectional view of the pressure P8 transmitted to the semiconductor sensor and the sealed liquid. FIG. 4 is a graph showing the relationship between the pressure P3 transmitted to the semiconductor sensor and the differential pressure p acting on the differential pressure transmitter. 31...Body, 34...Liquid junction path, 35.36
... Barrier diaphragm, 37 ... Filled liquid, 3
9...Semiconductor sensor, 42...Center diaphragm, 43.44...Fixing part. Patent Applicant Yamatake Honeywell Co., Ltd. Agent Yamakawa Administration (and 2 others) Figure 1 A 1 1 (1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A body having a liquid junction path with both ends open, a pair of barrier diaphragms fixed to the body and enclosing a pressure transmission medium in the liquid junction path, and a chamber communicating the liquid junction path with one surface of the semiconductor sensor. and a center diaphragm defining a chamber communicating with the other surface of the semiconductor sensor, and the pressure transmission medium of the semiconductor sensor has a cross-sectional area of a fixed portion of the body that supports the front and back surfaces of the center diaphragm. A differential pressure transmitter characterized in that the pressure is varied depending on the critical pressure for failure on the surface on which it acts.