KR860000776B1 - Differential pressure transmitter - Google Patents

Abstract

This invention is used to change the pressure difference between high pressure liquid and low pressure liquid into an electric signal using a semiconductor sensor. The differential pressure translator comprises a water pressure part and a sensor part, and they are separated. The liquid pressure is guided to both faces of the sensor through the way formed by both a water pressure part and a sensor part. High pressure liquid give pressure on the one face of the sensor through a high pressure seal diaphram and sealed liquid. Low pressure liquid gives pressure on the other face of the sensor through the low pressure seal diaphram and sealed liquid. After that, the pressure difference between high pressure liquid and low pressure liquid is changed into an electric signal through the resistor bridge of the sensor.

Description

Differential pressure transmitter

1 is a structural cross-sectional view of a differential pressure transmitter as one exemplary embodiment of the present invention.

2 is a detailed view of the sensor part of FIG.

3 is a detailed view of the seal metal body of FIG.

4 is an enlarged view of a part of the pressure receiving part of FIG.

5 is a view showing the relationship between the welding depth and the error.

6 shows the relationship between the weld width and the tension of the central diaphragm.

FIG. 7 is a view showing the pressure receiving part main body in a state in which the high pressure side seal diaphragm of FIG. 1 is not mounted. FIG.

The present invention relates to a differential pressure transmitter for converting a pressure difference between a high pressure fluid and a low pressure fluid into an electrical signal by a semiconductor sensor.

The semiconductor sensor of this type of differential pressure transmitter has a resistance pattern formed on a semiconductor substrate such as silicon by a diffusion technique. On one side of the semiconductor sensor the pressure of the high pressure fluid is applied through the high pressure side diaphragm and the high pressure side encapsulation liquid, and on the other side the pressure of the low pressure fluid is applied through the low pressure side diaphragm and the low pressure side encapsulation liquid. As a result, the pressure of the difference of the high pressure fluid is converted into an electric signal by the resistance bridge of the semiconductor sensor.

By the way, although such a differential pressure transmitter contributed to the improvement of the precision and reliability by using a semiconductor sensor, the differential pressure transmitter which was excellent in stability and compacted has the following requirements.

First, there should be no organic materials such as 0-rings or flexible printed plates in the area filled with the encapsulating liquid.

For example, when a flexible printed plate is used to take out an electrical signal of a semiconductor sensor or an organic material such as zero ring is used for sealing, these organic materials are played by the encapsulation liquid. The encapsulating liquid in which the organic material is melted may adversely affect the resistance pattern of the semiconductor sensor such as contamination or corrosion, and thus an accurate electrical signal cannot be obtained.

Secondly, it should be small so as to be influenced by partial pressure or static pressure.

The polarization effect refers to the fluctuation range of each zero point when the maximum working fluid is alternately applied to both sides of the semiconductor sensor and then removed. The positive pressure influence refers to the variation in the zero point when the maximum used fluid pressure is used on both sides of the zero point when no fluid pressure is applied to both sides of the semiconductor sensor.

Third, since both sides of the semiconductor oath are subjected to fluid pressure over a wide pressure range, overload protection is required to prevent such a situation that the semiconductor sensor is excessively displaced and damaged or destroyed due to excessive introduction fluid pressure.

Fourth, the hydraulic unit and the sensor unit should be separated, and the electrical signal from the sensor unit can be easily taken out, easy to manufacture, and compact.

An object of the present invention is to provide a differential pressure transmitter using a compact, semi-solid sensor having excellent stability that satisfies the above requirements.

The differential pressure transmitter according to the present invention has a structure in which the pressure receiving part and the sensor part are separated, and the semiconductor sensor installed in the sensor part has a single crystal with a thick circumferential part and a central part on the opposite side of the surface on which the resistance is formed. It consists of a silicon diaphragm and a support for supporting it through the circumferential portion of the silicon diaphragm, while the hydraulic pressure section is provided with overload protection of the semiconductor sensor inside the hydraulic section, in addition to the seal diaphragms facing the high and low pressure fluids installed on both sides thereof. The center diaphragm is installed. The fluid pressure is directed to both sides of the semiconductor sensor through the pressure passages provided in the hydraulic pressure section and the sensor section.

In the sensor section, the surface on which the semiconductor sensor resistance is formed is disposed so as to face the pressure receiving section.

1 is a structural cross-sectional view of a differential pressure transmitter according to an embodiment of the present invention.

In the figure, in the differential pressure transmitter, the pressure receiving part 1 and the sensor part 100 have a separate structure. The hydraulic part 1 has two hydraulic part bodies 2 and 3, which are made of stainless steel, for example. As shown in the drawing, the pressure receiving body 2 is formed so that its cross section is substantially C-shaped, and the pressure receiving body 3 is fitted to the pressure receiving body 2. A central flexible diaphragm 4 is provided between the hydraulic subsidiary bodies 2 and 3, thereby providing two isolation chambers between the hydraulic subsidiary bodies 2 and 3. 5), 6 are formed. The central diaphragm 4 is made of stainless steel having greater rigidity than the high pressure side diaphragm 7 and the low pressure side diaphragm 8 described later. The circumferential portion of the central diaphragm 4 is electromagnetic beam welded to the hydraulic part main body 2, and is again welded to the hydraulic part main body 3 with the hydraulic part main body 3 fitted to the hydraulic part main body 2.

The corrugated high pressure side seal diaphragm 7 and the low pressure side seal diaphragm 8 are provided outside the hydraulic part main body 2 and 3, respectively, and the high pressure hydraulic chamber is provided between the main body 2 and 3, respectively. (9) and the low pressure hydraulic chamber 10 are formed. Both diaphragms 7 and 8 are each made of stainless steel with good corrosion resistance and corrosion resistance, and the periphery is fixed to the main body 2 and 3 by electron beam welding. The high pressure side isolation chamber 5 and the high pressure side hydraulic pressure chamber 9 communicate with each other by the pressure-pressure path 11, and likewise, the low pressure side isolation chamber 6 and the low pressure-side pressure pressure chamber 10 are connected by the pressure pressure path 12. In communication. A pressure damper 13 for suppressing sudden pressure fluctuations and pulsations of the high-pressure fluid is formed in the pressure-guide path 11 on the high pressure side.

In this way, the hydraulic part body having three diaphragms (4), (7), and (8) is connected to the high pressure side flange (14) and the low pressure side flange (15) through the packings (30) and (31). ) Is fixed by the nut 17. The high pressure side flange 14 has a high pressure fluid guide port 18 through which a high pressure fluid flows, and a chamber in which the high pressure fluid is applied to the seal diaphragm 7, that is, a high pressure fluid chamber 19. To form. Similarly, the low pressure side flange (5) also has a low pressure fluid pressure port 20, and forms a low pressure fluid chamber 21. The hydraulic pressure main bodies 2 and 3 have an isolation chamber on the high pressure side and the low pressure side. 5) and 6, the high pressure side conduction path 22 and the low pressure side conduction path 23 for applying the fluid pressure to the semiconductor sensor 108 mentioned later are provided.

As described above, one hydraulic part body 2 is formed in a substantially C shape, and the other hydraulic part body 3 is configured to fit the hydraulic part body 2, and the high pressure side flange 14 ) And the low pressure side flange 15 are clamped and fixed only to the hydraulic pressure unit body 2, so that adverse effects such as deformation of the central diaphragm 4 due to this tightening can be minimized.

Here, the chambers (5), (6), (9), (10) formed by the hydraulic body (2), (3) and three diaphragms (4), (7), and (8) or the pressure path ( 11), (12), (22), (23) and both surfaces of the semiconductor sensor 108 described later have good insulating properties, for example, silicon oil, and an incompressible liquid is a liquid seal 24 Enclosed by (25). After the sealing, the liquid sealing passages 24 and 25 are sealed by the stoppers 26 and 27. A steel ball 28 is inserted into the side facing the center diaphragm 4 of the liquid sealing passage 24 on the high pressure side. The diameter of the steel ball 28 is larger than the diameter of the liquid sealing passage 24.

Next, the sensor unit 100 will be described. The sensor unit 100 is composed of the connecting metal body 102, the seal metal body 103, and the details of the connecting airflow housing 104 as a whole. The connecting metal body 102 has a pressure passage 105 in communication with the pressure passage 22 on the high pressure side of the hydraulic subsidiary bodies 2 and 3 and a pressure passage 106 in communication with the pressure passage 23 on the low pressure side. ) The connecting metal body 102 is made of stainless steel, and the contact surface with the hydraulic part 2 is joined by electron beam welding. Since the differential pressure transmitter shown in this embodiment uses only the flanges 14 and 15 according to the diameter of the pipe to which it is mounted, the size of the connecting metal body 102 is determined according to the maximum diameter of the used pipe.

Next, the seal metal body 103 will be described. The details are as shown in FIG. 2, and FIG. 2 (a) is an enlarged view of the seal metal body of FIG. 1, and FIG. 2 (b) is a view of the seal metal body as seen from the arrow A direction.

First, a semiconductor sensor 108 made of a silicon single crystal is bonded to a hollow support 107 made of, for example, a Fe-Ni alloy or a Fe-Ni-Co alloy. Although the bonding method may use a bonded body such as a gold-silicon eutectic alloy, the semiconductor sensor 108, the glass layer, and the support 107 may be formed by interposing a thin glass layer between the bonding surfaces of both. Joining by a known anode bonding method is effective in terms of airtightness, static pressure, and bias pressure. The support 107 may be formed of a material having substantially the same thermal expansion coefficient as that of the semiconductor sensor 108 and having the same properties as the Young's modulus. On the other hand, the semiconductor sensor 108 has a thick circumferential portion and a central portion bonded to the support 107, and the resistance pattern is opposite to the support 107, that is, the surface of the ceramic protective cover 110 side. In other words, the flesh is formed into a thick central part and a thinner part closer to the periphery. In addition, the semiconductor sensor 108 is an n-type single crystal silicon, and the crystal plane is a plane of 110, and the resistance pattern is preferably formed along the radial direction of the <111> axis direction where the sensitivity is maximized by a p-type gauge. The resistance pattern is wired by a donut-shaped ceramic substrate 109 disposed on the seal metal body 103 so as to surround the semiconductor sensor 108 to form a Wheatstone bridge. Wiring between the semiconductor sensor 108 and the ceramic substrate 109 is made by a lead wire 111 coupled with a wire. On the other hand, the lead wire 113, which takes out an electrical signal from the ceramic substrate 109 to the outside, penetrates the seal metal body 103 and one end portion thereof comes out to the outside, and the seal between the seal metal body 103 and the outside is mechanical By the seal 114. The other end of the lead wire 113 is soldered to the ceramic substrate 109. A ceramic protective cover for protecting the resistance pattern of the semiconductor sensor 108 or the lead wire 111 is attached to the seal metal body 103 by the push pin 112.

In this way, the seal metal body 103 on which the semiconductor sensor 108 is mounted is joined to the connecting metal body 102 by electron beam welding, and then the plate 115 is also sealed by electron beam welding. It is bonded to 103. The seal metal body 103 or the plate 115 is preferably made of stainless steel.

As a result, the space in which the high pressure fluid pressure and the low pressure fluid pressure acting on both surfaces of the semiconductor sensor 108 is completely partitioned and also completely sealed to the outside, and both spaces are sealed as described above. The fluid pressure on the low pressure side acts on one side of the semiconductor sensor 108 through the pressure path 106, the pressure path 116 formed of the sealing metal body 103 and the plate 115, and the hollow portion of the support 107. do. On the other hand, the fluid pressure on the high pressure side is divided into the pressure path 105, the space partitioned by the connecting metal body 102 and the ceramic protective cover 110, the ceramic protective cover 110 and the other side of the semiconductor sensor 108 It acts on the other side of the semiconductor sensor 108 through space.

With such a structure, since no organic substance exists at all in the space filled with the encapsulating liquid, adverse effects on the semiconductor sensor 108 due to the organic substance can be prevented. Further, by thickening the central portion of the semiconductor sensor 108, good results were obtained that the polarization effect and the static pressure effect were very small. This is considered to be for the following reason.

That is, when a positive pressure is applied to the semiconductor sensor 108, a strain component that is compressed and a strain component that is tensioned in the radial direction are generated in the resistance pattern caused by the action of the thick portion. However, these two strains cancel each other out, resulting in no variation in output. Of course, the same applies to the bias.

Thus, the semiconductor sensor with a thick central portion has the following advantages as a differential pressure transmitter. The high pressure fluid inlet and the low pressure fluid inlet are not always fixed, and may be used by switching between high pressure and low pressure. In this case, the conventional device does not have the same output characteristics as when the low pressure is applied and when the high pressure is applied, so it is necessary to install a control mechanism for adjusting this, and the time-consuming adjustment is necessary. there was. However, if the present embodiment is employed, the output characteristics do not change even when either low or high pressure is applied, so that the conventional adjusting mechanism is unnecessary and not cumbersome.

Here, the overload protection will be described. The central diaphragm 4 is a hydraulic diaphragm 2 or ( Even if it is seated in 3), the center diaphragm 4 has rigidity of a predetermined size so that the center diaphragm 4 does not seat in the hydraulic part body 2 or (3). Moreover, the volume of the high pressure side import chamber 9, the high pressure side isolation core 5, or the low pressure side hydraulic pressure chamber 10, and the low pressure side isolation chamber 6 is formed so that an isolation chamber side may become large. Therefore, even if the high pressure side or the low pressure side diaphragm 7, 8 is seated on the hydraulic body 2, 3 by the overload pressure, the central diaphragm 4 is the hydraulic body 2, 3. Don't sit on As a result, since an increase in the pressure of the encapsulating liquid is prevented, the overload pressure does not act on the semiconductor sensor 108, and deterioration and damage of the characteristics of the semiconductor sensor 108 can be prevented.

Then, when a high pressure fluid such as a process fluid is introduced from the high pressure fluid tool 18 of the high pressure side flange 14, the pressure of the high pressure fluid is the high pressure side diaphragm 7, the pressure path 11, and the high pressure side isolation chamber 5. And acts on one side of the semiconductor sensor 108 via the conducting furnaces 22 and 105. Similarly, when the low pressure fluid is also introduced from the low pressure fluid inlet 20 of the low pressure side flange 15, the pressure of the low pressure fluid is controlled by the low pressure side diaphragm 8, the pressure path 12, the low pressure side isolation chamber 6, and the pressure path. It acts on the other side of the semiconductor sensor 108 via (23), (106), (116). As a result, the semiconductor sensor 108 is bent in accordance with the pressure difference of the semiconductor sensor 108, thereby changing the resistance value of the resistance pattern. This resistance change reaches the amplifier through the lead wire 111, the ceramic substrate 109, and the lead wire 113, and the pressure difference is displayed. This prevents excessive fluid pressure from being transferred to either side of the semiconductor sensor 108 through the encapsulation liquid, thereby preventing damage or destruction of the semiconductor sensor 108.

And as shown in FIG. 1, even if the sealing metal body 103 uses materials with good corrosion resistance, such as stainless steel, it is exposed to high temperature in the mechanical seal 114, a number of welding places, etc. And corrosion resistance may fall. Differential pressure transmitters are often used in places where the environment of chemical plants is not very good, and corrosion resistance must be considered. The seal metal cover 117 of FIG. 1 is a protective cover of stainless steel used for that purpose. The detail of this seal metal body cover 117 is shown in FIG. Fig. 3 (a) is a cross sectional view thereof, and Fig. 3 (b) is a view as seen from the direction of arrow B. As shown in the drawing, a thick portion and a thin portion are formed, and the thick portion is a groove having a zero ring 122 formed therein. Is formed. The tip of the thin portion is joined to the connecting metal body 102 shown in FIG. 1 by electron beam welding.

As shown in FIG. 1, the connector cover 118 is electromagnetic beam welded to the end of the thick portion of the seal metal cover 117, and the connector cover 118 forms the connector airflow housing 104. As shown in FIG. The connecting airflow storing unit 104 includes a lead wire 113 and a compensating substrate 120 mounted with dermistors for compensating an electric signal of the semiconductor sensor 108 spoken by the lead wire 113 by temperature. And a flexible printed circuit board 119 for electrically connecting them, and a binder 121 for electrically connecting with an amplifier (not shown). The amplifying unit is to be housed in the amplifying unit body case 200. The amplifier unit amplifies an electric signal corresponding to the differential pressure between the high pressure fluid and the low pressure fluid detected by the semiconductor sensor 108 to generate a signal displayed on the meter, or to generate an output signal for transmission to the outside.

The amplification part body case 200 is fixed to the connecting metal body 102 by a fixing screw 201 via the 0 ring 122.

4 is a partial detailed view of the hydraulic unit. As described above, the hydraulic subsidiary body 2 is formed in a substantially C-shape, the hydraulic subsidiary body 3 is fitted to the hydraulic subsidiary body 2, and both are joined by electron beam welding. The electron beam welding prevents the hydraulic pressure unit body from being deformed under the condition of positive pressure and partial pressure. That is to increase the rigidity of the body. However, when the pressure is relatively low, there is no problem. However, when the pressure is high, the upper and lower portions of the hydraulic pressure unit 2 deform, and an error appears. To prevent this, increase the rigidity of the body. That is, although the thickness of a main body may be thickened, there exists a problem of becoming large. Therefore, it has been found that the electron beam welding depth D may be deepened, and furthermore, the welding depth D may be 4 mm or more to freeze within 0.2% of the error required for maintaining the long-term stability performance as the differential pressure transmitter.

Next, mounting of the center diaphragm 4 is demonstrated. What is required as the center diaphragm is that the same characteristics are applied when the same pressure is applied from the high pressure side and the low pressure side, and for this purpose, it is necessary to solve the following two problems.

(1) Match the movable area of the center diaphragm with the high pressure side and the low pressure side.

(2) Tension is applied to the center diaphragm to remove the deflection of the center diaphragm.

For this purpose, the projected part 3 is provided with the protrusion part 3A in the hydraulic-pressure part main body 3, and it presses the inside of the welding part of the center diaphragm 4 with this protrusion part 3A. As a result, since the movable area of the center diaphragm 4 is determined by the protrusion part 3A, it can match with the high pressure side and the low pressure side. Moreover, about the subject (2), it achieved by setting the welding width W with respect to the hydraulic part main body 2 of a central diaphragm to an optimal value. That is, as shown in FIG. 6, when the welding width W is widened, the tension of the center diaphragm increases. The ideal tension of the center diaphragm 4 is 5-10 kg / mm ² , and the welding width W for releasing this tension is preferably equal to the plate thickness B of the center diaphragm 4, and the welding width W ) Is set to 0.5-2 times the thickness of the center diaphragm 4, so that the ideal tension range in FIG.

As described above, the pressure receiving unit 1 having the pressure receiving unit bodies 2 and 3 and the sensor unit 100 including the connecting metal body 102, the sealing metal body 103, and the connecting airflow storing unit 104. ), The differential pressure transmitter is configured by separating and stacking each function separately, so that it is easy to manufacture and has a compact structure.

FIG. 7 is a view of the pressure-receiving surface of the pressure-receiving portion main body 2 without the high-pressure side diaphragm shown in FIG. That is, the groove 29 is formed in the radial direction passing through the damper 13 and the liquid sealing passage 24. For example, in the structure in which the groove 29 is not provided, the high pressure side pressure receiving chamber 9 and the high pressure are formed. The pressure passage communicating with the side isolation chamber 5 is the only one pressure passage 11 provided at the center of the hydraulic pressure main body 2. For this reason, when fluid pressure acts, delivery of the sealing liquid enclosed in the hydraulic chamber 9 may become slow, and responsiveness may worsen. For this reason, as shown in FIG. 7, the groove 29 is formed in the hydraulic pressure main body 2, and the delay of delivery of a sealing liquid is improved.

Of course, in Fig. 7, the pressure receiving main body 2 on the high pressure side is shown, but the same groove is formed in the pressure receiving main body 3 on the low pressure side.

As described above, according to the present invention,

First, there is no organic substance in the space filled with the encapsulation liquid.

Second, the bias and static pressure effects are very small.

Third, it has overload protection.

In addition to excellent stability, a differential pressure transmitter using a semiconductor sensor which is easy to manufacture and compact can be obtained.

Claims (1)

(Correction) A hydraulic pressure unit main body, two seal diaphragms forming a hydraulic pressure chamber of high pressure fluid and a low pressure fluid on both side surfaces of the hydraulic pressure main body, and the hydraulic pressure chamber inside the hydraulic pressure main body. A pressure receiving portion having a central diaphragm which forms an isolation chamber in communication with each other, a silicon single crystal semiconductor sensor having a resistance pattern formed on one side thereof, and having a peripheral portion and a central portion thickened on the other side thereof, and the other side of the semiconductor sensor. A support having a hollow portion joined to the periphery of the first portion, the support being fixed to the first preservation furnace for guiding a first fluid pressure to the other side of the semiconductor sensor through the hollow portion of the support. A seal metal body for forming a second conduction path for guiding a second fluid pressure on one side of the semiconductor sensor and the second conduction path of the seal metal body; A ceramic substrate arranged in contact with the conductor sensor and wired to take out an electrical signal according to the pressure obtained by the semiconductor sensor, and a mechanical seal mounted on the seal metal body to take out an electrical signal from the ceramic substrate to the outside. Third and fourth pressure pressures for guiding the fluid pressure from one hydraulic chamber to each of the first and second pressure paths, and the connector housing portion for storing the lead wire, the connector air connected to the lead wire, and the first and second pressure paths. It is configured as a sensor unit having a connecting metal body forming a furnace, and an incompressible sealing liquid having insulation is enclosed in a space in which fluid pressure is guided on both sides of the semiconductor sensor, and the surface on which the resistance pattern of the semiconductor sensor is formed is A differential pressure transmitter, characterized in that disposed so as to face the pressure receiving body.

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