JPH0643057A - Excessive-pressure protecting mechanism of differential-pressure transmitter - Google Patents

Abstract

PURPOSE:To protect the excessive pressure of a differential-pressure transmitter by outputting the differential pressure between the first pressure, which is applied to a recess part, and the second pressure, which is applied to the other side of a single- crystal substrate and obtained through a pressure guiding hole, into a sensor part. CONSTITUTION:When a low pressure PL is applied to a sealing diaphragm 57, the pressure is applied on sealed liquid 73 in an excessive-pressure protecting mechanism 23 and also applied to a recess part 38. Meanwhile, when a high pressure PH is applied to a sealing diaphragm 31, the pressure is applied to sealed liquid 44 in an excessive- pressure protecting mechanism 22 and also applied to a recess part 64. When the pressure difference DELTAP between the low pressure PL and the high pressure PH is in the specified range, valves 69 and 43 do not close through holes 66 and 32. Therefore, the pressure difference DELTAP is applied to a thin part 52 of a sensor part 26, and the corresponding signal is outputted. When the high pressure PH is applied, a coupling part 42 closes a through hole 40 and prevents the excessive pressure for the sensor part 26. When the excessive pressure is applied to the side of the low pressure PL, the valve 69 closes the through hole 66, and the transmission of the excessive pressure to the sensor part 26 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention receives a high pressure and a low pressure (or reference pressure) measured pressure, and a differential pressure (or pressure) between them.
The present invention relates to an overpressure protection mechanism of a differential pressure transmitter for detecting a pressure difference, and more particularly to an overpressure protection mechanism of a differential pressure transmitter improved so as to enable static pressure / overpressure protection with a small and inexpensive structure.

[0002]

2. Description of the Related Art A differential pressure transmitter is configured to apply a measuring pressure to a pressure-receiving diaphragm on a high-pressure side and a pressure-receiving diaphragm on a low-pressure side, and to take out the movement of a sealing liquid by this pressure as an electric signal due to, for example, distortion of a semiconductor sensor. There is. However, this type of differential pressure transmitter may sometimes be subjected to excessive pressure or static pressure, and this excessive pressure or static pressure may reach the semiconductor sensor and damage it, making subsequent measurement impossible. .

Therefore, conventionally, various structures have been proposed to protect the sensor from the excessive pressure and static pressure. Figure 1
Reference numeral 0 is a sectional view of a conventional differential pressure transmitter having this type of overpressure / static pressure protection structure. Hereinafter, description will be given based on FIG. A high-pressure side pressure-receiving diaphragm 2 and a low-pressure side pressure-receiving diaphragm 3 formed in a corrugated disc shape are mounted on both sides of the body 1 in a half-divided shape. High pressure and low pressure are applied by the fluids flowing in through the holes 5 and 6 between the cover 4 and the body 1 on both sides which are bolted to 1.

On the other hand, the sensor capsule 7 above the body 1
In the inside of the sensor chamber, a semiconductor sensor 8 connected to a terminal (not shown) is joined and held by a substrate 9, and a high pressure side 8a below the sensor 8 and a low pressure side 8b above the sensor 8 It is connected to the high pressure side and the low pressure side of the body 1 via passages 10 and 11. In this way, the sensor 8 has a high voltage side 8a.
Since the sensor 8 is bonded to the substrate 9, the low pressure side 8b is weak against the pressure in the direction from the upper side to the lower side.
This is because the pressure from the opposite direction is relatively strong and the pressure resistance is directional.

Reference numeral 12 denotes a center diaphragm formed in the shape of a corrugated disc. The center diaphragm 12 has an inner chamber provided at the central joint portion of the body 1 as a high pressure side inner chamber 13 and a low pressure side inner chamber 14. It is fixed to the body 1 so as to be separated from and. The liquid passages 10 and 11 are the inner chamber 1 of the main body.
3 and 14 are opened respectively. Further, the gaps formed between the pressure receiving diaphragms 2 and 3 and the body 1 and the main body inner chambers 13 and 14 are connected by liquid passages 15 and 16, respectively.

Then, the liquid passages 15 and 16 and the inner chambers 13 and 14 are inserted through the gaps between the pressure receiving diaphragms 2 and 3 and the body 1.
Further, between the high pressure side 8a and the low pressure side 8b of the sensor 8 via the liquid passages 10 and 11, a sealing liquid 1 such as silicone oil is provided.
7 is enclosed.

In the above structure, when a high pressure and a low pressure are applied to the pressure receiving diaphragms 2 and 3, respectively, as measuring pressures, the pressure receiving diaphragms 2 and 3 bend and the sealing liquid 17 moves by the amount of compression due to the bending, and the pressure on both sides is increased. Sealing liquid due to the difference 17
The sensor 8 detects the difference in the amount of movement of the sensor and sends it as an electric signal to measure the differential pressure. In this case, the center diaphragm 12 is deformed by the pressure difference between the two sides, but does not contact the wall surfaces of the main body inner chambers 13 and 14. Also,
The pressure receiving diaphragms 2 and 3 also do not contact the body 1 in the normal differential pressure measurement range.

Here, for example, when an excessive pressure acts on the high pressure side, the pressure receiving diaphragm 2 on the high pressure side is largely deformed and comes into full contact with the body 1, so that the pressure on the high pressure side is further transmitted to the inside. The sensor 8 is protected from overpressure due to the elimination of the pressure-receiving diaphragm 2 on the body 1. Such a protective function is the same when an overpressure is applied to the low pressure side.

[0009]

However, in the differential pressure transmitter as described above, since the metal pressure receiving diaphragm is seated on the metal body to realize the overpressure protection of the sensor, the form is different. It gets bigger and heavier,
In addition, there is a problem in that the characteristics of the material itself cause plastic deformation and adversely affect the characteristics of the differential pressure transmitter.

[0010]

In order to solve the above problems, the present invention provides a thin-walled portion formed by forming a recess on one side of a thick single-crystal substrate and a single-crystal substrate. A pressure guiding hole provided therethrough, a fixing part provided in the thick part of the single crystal substrate, a coupling part that is coupled to the thin part above, and a valve part provided opposite to the pressure guiding hole. And a beam-shaped beam provided on the other side of the previous single crystal substrate, and the first pressure applied to the previous recess and the other side of the previous single crystal substrate. The differential pressure from the second pressure obtained through the pressure guiding hole is output to the sensor section to protect the differential pressure transmitter from excessive pressure.

[0011]

[Operation] When no differential pressure is applied, the pressure guide hole and valve are open, and when the first pressure is applied, the thin wall part is displaced and the beam fixing part is used as a fulcrum through the connecting part. The valve portion is displaced toward the pressure guiding hole side to close the pressure guiding hole and cut the overpressure as an overrange.

Here, when the second pressure is further applied, the operation reverse to the above is performed and the valve portion is displaced in the direction of opening the pressure guiding hole with the fixed portion of the cantilever as the fulcrum through the coupling portion. ,
When the differential pressure between the first pressure and the second pressure enters a predetermined range, the valve section opens the pressure guiding hole and outputs the differential pressure to the sensor section as usual.

In this way, when the excessive pressure is applied, the valve portion is prevented from closing the pressure guiding hole and the excessive pressure is prevented from being applied to the sensor portion, and the static pressure is applied to the pressure guiding hole. The valve section opens to output the differential pressure between the first pressure and the second pressure to the sensor section.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention. Numerals 20 and 21 are, for example, cylindrical bodies made of kovar or the like, and inside these bodies 20 and 21, there are cylindrical vacant chambers 2 for accommodating overpressure protection mechanisms 22 and 23.
4, 25 are formed. In the body 20, a vacant chamber 27 for accommodating the sensor section 26 is formed near the vacant chamber 24. These bodies 20 and 21 have a joint surface 28.
Are joined together at.

A circular recess 30 is formed in the center of an upper pressure receiving surface 29 opposite to the joint surface 28 of the body 20.
A thin seal diaphragm 3 formed inside the
1 is covered. A through hole 32 is formed from the recess 30 toward the empty room 24.

The overpressure protection mechanism 22 is bonded to a plate-shaped substrate 33 made of Pyrex glass by anodic bonding or the like, and the substrate 33 is bonded to the bottom of the vacant chamber 24 by low-melting glass bonding or the like. In addition, this substrate 33
A through hole 34 for introducing the low pressure P _L and a through hole 35 for introducing the high pressure P _H are formed through the substrate 33.

The overpressure protection mechanism 22 is composed of a silicon substrate 36 made of a plate-shaped single crystal of silicon and a cantilever beam 37 made of polysilicon formed thereon. The silicon substrate 36 has a thin portion 39 that functions as a diaphragm by etching a portion near the right end of the silicon substrate 36 to form a recess 38.
A through hole 34 is opened in the. Further, a through hole 40 communicating with the through hole 35 is formed in a portion of the silicon substrate 36 away from the recess 38.

The fixed portion 41 of the cantilever 37 is a silicon substrate 3
The thin portion 39 of the silicon substrate 36 and the beam portion of the cantilever 37 corresponding thereto are fixed to one end of the thick portion 6 of the connecting portion 4
Are joined by two. The portion of the cantilever beam 37 near the end portion on the opposite side of the fixed portion 41 and the portion facing the through hole 40 are closely arranged so that the through hole 40 can be closed.
Are formed.

A sealing liquid 44 such as silicon oil is enclosed in the recess 30, the through holes 32 and 35, the chambers 24 and 27, and the through hole 40.

Further, from the bottom of the vacant chamber 24 to the through holes 34, 3
Through-holes 45, 46 communicating with 5 are formed toward the joint surface 28, and the through-hole 46 is also opened in the vacant chamber 27 via the through-hole 47.

The excessive pressure protection mechanism on the body 21 side is basically constructed in substantially the same manner as the body 20 side. However, the central upper surface portion 50 on the joint surface 28 side of the body 21 is formed so that the sensor portion 26 is housed in the empty chamber 27.
It is affixed on top of 0 by low melting glass bonding.

The sensor portion 26 has a silicon substrate 53 having a thin portion 52 formed by a recess 51 formed by etching the central portion, and a strain sensing element (such as a vibration type sensor) formed in the thin portion 52 ( (Not shown) and a glass substrate 54 made of Pyrex glass or the like which is joined to the thick portion of the silicon substrate 53 by anodic bonding or the like. The glass substrate 54 has a through hole 55 in the central portion and is bonded to the central upper surface 50 of the body 21 with a low melting point glass.

A circular recess 56 is formed in the center of the lower pressure receiving surface 55 on the side opposite to the joint surface 28 of the body 21.
Formed on the inside of the thin seal diaphragm 5
7 covers. A through hole 58 is formed from the recess 56 toward the empty chamber 25.

The overpressure protection mechanism 23 is bonded to a plate-shaped substrate 59 made of Pyrex glass by anodic bonding or the like, and the substrate 59 is bonded to the upper part of the chamber 25 by low-melting glass bonding or the like. In addition, this substrate 59
A through hole 60 for introducing the low pressure P _L and a through hole 61 for introducing the high pressure P _H are formed through the substrate 59.

The overpressure protection mechanism 23 comprises a silicon substrate 62 made of a plate-shaped single crystal of silicon and a cantilever beam 63 made of polysilicon formed thereon. The silicon substrate 62 has a thin portion 65 that functions as a diaphragm by etching a portion near the left end of the silicon substrate 62 to form a recess 64.
A through hole 61 is opened in the. Further, a through hole 66 communicating with the through hole 60 is formed in a portion of the silicon substrate 62 which is apart from the recess 64.

The fixed portion 67 of the cantilever 63 is a silicon substrate 6
The thin-walled portion 65 of the silicon substrate 62 and the corresponding beam portion of the cantilever 63 are fixed to one end of the thick-walled portion 2 of the connecting portion 6.
Connected by eight. The portion of the cantilever 63 facing the through hole 66 in the vicinity of the end portion on the opposite side of the fixed portion 67 is closely arranged so that the through hole 66 can be closed.
Are formed.

Further, from the bottom of the vacant chamber 25 to the through holes 45, 4
Through holes 70, 71 communicating with 6 are formed toward the joint surface 28, and the through hole 70 is also opened in the recess 51 via the through hole 72. These recesses 56 and through holes 5
8, vacant chamber 25, through holes 66, 60, 70, 72, 55,
A sealing liquid 73 such as silicon oil is sealed in the recess 51, the through holes 45 and 34, and the recess 38.

In these structures, the thin portions 39, 65
The valve 43, 69 can be largely displaced even if the valve is thicker, even if the pressure difference is minute due to the lever principle of the cantilevers 37, 63. Further, since the valves 43 and 69 are sealed by the shearing force, it is possible to prevent leakage at these parts by increasing this area. In these cases, even if the thin portions 39 and 65 are largely bent by excessive pressure, appropriate thicknesses and widths of the cantilever beams 37 and 63 should be selected to prevent excessive stress. You can also

FIG. 2 is a perspective view showing the structure of the overpressure protection mechanism 22 described above. The overpressure protection mechanism 23 has a similar structure.

In the above structure, when the low pressure P _L is applied to the seal diaphragm 57, this pressure is applied to the sealing liquid 73 outside the overpressure protection mechanism 23 and the recess 38.
Is also applied. On the other hand, when the high pressure P _H is applied to the seal diaphragm 31, this pressure is applied to the sealing liquid 44 outside the overpressure protection mechanism 22 and also to the recess 64.

The differential pressure ΔP between these low pressure P _L and high pressure P _H
Is within a predetermined range, the displacement of the coupling portions 68, 42 of the cantilever beams 63, 37 is small, so that the valves 69, 43
Does not close the through holes 66, 32, respectively, but is in an open state. Therefore, the differential pressure ΔP is directly applied to both sides of the thin portion 52 of the sensor unit 26, and a signal corresponding to this differential pressure ΔP is output from the strain sensing element.

However, for example, when the high pressure P _H is applied as a large overpressure exceeding a predetermined range, the connecting portion 4
2 is displaced in the direction of closing the valve 42 and closes the through hole 40, thereby preventing an excessive pressure from being applied to the sensor portion 26. When an overpressure is applied to the low pressure P _L side, the valve 69 closes the through hole 66 to prevent the overpressure from being transmitted to the sensor unit 26 in the same manner as the high pressure side. As described above, the overpressure prevention is executed.

FIG. 3 is a process diagram showing an outline of a manufacturing process for manufacturing the portion of the overpressure protection mechanism by a semiconductor process. The excessive pressure protection mechanism 22 will be described as an example. 3 (a) is oxidized over a silicon substrate 74, using a mask after the window opened to a cantilever 37 oxide film a gap portion opposed to the silicon substrate 36 thick of (S _i O ₂₎ The first oxidation step for securing as 75 and 76 is shown.

FIG. 3B shows a second oxidation step of forming a thin oxide film 77 connected to the outside of the oxide film 75 on the chip obtained in the first oxidation step. This oxide film 77
Determines the size of the gap formed between the bulb 43 and the silicon substrate 36. In this step, the through hole 40 is further formed in the silicon substrate 74 by, for example, laser processing.

FIG. 3C shows a depositing step of depositing polysilicon 78 on the oxide films 75, 76 and 77 for the chips obtained in the second oxidizing step. By this step, the prototype of the cantilever beam 37 is formed. FIG. 3D shows an etching process for removing the oxide films 75, 76, 77 from the chip obtained in the depositing process of FIG. 3C. The cantilever beam 37 is formed by this process.

FIG. 3E shows a diaphragm forming step for forming the thin portion 39. In this process, the silicon substrate 74
The thin portion 39 is formed by etching from a predetermined position on the lower side to form the concave portion 38. As described above, the overpressure protection mechanism 22 is manufactured in the semiconductor manufacturing process.

FIG. 4 is a vertical sectional view showing the construction of the second embodiment of the overpressure protection mechanism formed on the substrate. FIG. 5 is a perspective view of the overpressure protection mechanism shown in FIG. In the embodiment shown in FIG. 1, overpressure protection is realized by using a cantilever beam, but in this configuration, it is realized as a support beam at both ends.

Reference numeral 80 denotes a plate-shaped substrate made of Pyrex glass or the like. The substrate 80 has a through hole 81 penetrating at the center and a pair of through holes 8 penetrating on both sides thereof.
2, 83 are formed. A plate-shaped silicon substrate 84 is bonded onto the substrate 80 by anodic bonding or the like, and a pair of recesses 85 and 86 is formed in the bottom of the silicon substrate 84 by etching or the like to form a thin portion 87 that functions as a diaphragm. 88 is formed. Further, a through hole 89 communicating with the through hole 81 is formed in the central portion of the silicon substrate 84.

On the silicon substrate 84, both-end supporting beams 90 made of polysilicon or the like are provided at both end portions 91, 92.
It is fixed in one. A flat valve portion 9 is formed in the center of the both-ends supporting beam 90 so as to face the through hole 89 and slightly project.
3 is formed. Both ends 9 of this both-end support beam 90
Coupling portions 94 and 95 connected to the thin portions 87 and 88 are formed near the portions 1 and 92.

According to this structure, the lateral displacement due to the displacement of the thin portion when an excessive pressure is applied can be eliminated, and the force for opening the closed through hole 89 can be increased. In addition, the valve part 9
The material of 3 may be a single crystal silicon nitride film other than polysilicon.

FIG. 6 is a longitudinal sectional view showing the structure of a peripheral structure including an overpressure protection mechanism according to the present invention, and FIG. 7 is an A- line shown in FIG.
It is the top view seen from A '. In these structures, each part is partially formed in a wafer shape, and these wafers are bonded to each other by, for example, direct bonding to form an overpressure protection mechanism.

In this embodiment, the center point P of XX 'in FIG.
On the other hand, the upper and lower structures are formed point-symmetrically. That is, silicon single crystal wafers-96A, 97A, 98A
The wafers 96B, 97B and 98B are point-symmetrical. These wafers are bonded to each other by, for example, direct bonding.

The wafer 96A has a concave portion 100A formed on the pressure receiving surface 99A side, and a thin seal diaphragm 101A is fixed on the concave portion 100A in a liquid-tight manner. Recess 100A
A through hole 102A is formed in the central portion of the above so as to penetrate a vacant chamber 103A formed on the side opposite to the pressure receiving surface 99A.

The wafer 97A has a hole 104A formed in the center thereof, and the hole 104A is sized so as to coincide with the side surface of the vacant chamber 103A. The wafer 98A is formed with a through hole 105A for leading out the high pressure P _H and a through hole 106A for leading out the low pressure P _L.
Pressure lead-out holes _TH and _TL leading to the sensor section corresponding to the sensor section 26 are provided on the XX 'surface side of 5A and 106A.

Wafer 98A vacant chamber 103A, hole 104
In A, an overpressure protection mechanism 22A similar to the overpressure protection mechanism 22 is provided. A sealing liquid 107A is sealed outside the overpressure protection mechanism 22A. Sign B in the numbers
The lower side marked with is also configured similarly to the A side, and the operation is almost the same as that described in FIG.

FIG. 8 is a longitudinal sectional view showing the structure of another peripheral structure including the overpressure protection mechanism according to the present invention. In the configuration shown in FIG. 1, a pair of overpressure protection mechanisms are arranged vertically, and the sensor section is arranged at the center of these, but in the configuration shown in FIG. 8, a pair of overpressure protection mechanisms are arranged left and right. However, the sensor unit is separately prepared.

Like the body 20, the body 108 is made of metal such as kovar. On this upper part, a metal flange 10 for introducing high pressure P _H and low pressure P _L
9 are connected. The flange 109 is formed with pressure introduction holes 110A and 110B on the left and right, respectively, and recesses 111A and 111B are formed on the lower side thereof.

At the upper end of the body 108 corresponding to the recesses 111A and 111B, a pair of seal diaphragms 112A and 112B are formed below the recesses 11 respectively.
It is fixed in a liquid-tight manner by covering 3A and 113B. A through hole 114A is formed in the center of these recesses 113A and 113B.
114B communicates with a pair of empty chambers 115A and 115B formed inside the body 108.

Substrate 117 is provided with overpressure protection mechanisms 116A and 116B similar to overpressure protection mechanisms 22 and 23 shown in FIG. 1 at the bottoms of chambers 115A and 115B, respectively.
It is fixed through A and 117B. Further, high pressure P _H ,
Through holes 116A, 117A and 116 for leading out the low pressure P _L
B and 117B penetrate the bottom of the body 108. The through-holes 116A and 116B are led out through the pipe 118, and the through-holes 117A and 117B are led out through the pipe 119 to the high pressure P _H and the low pressure P _L , respectively, and supply them to a sensor unit (not shown) similar to the sensor unit 26.

FIG. 9 shows an outline of a manufacturing process for manufacturing an example of a structure for enhancing the sealing property between the valve and the through hole when the valve of the overpressure protection mechanism is closed.
In this case, a case where the fitting portion between the valve 43 and the tip of the through hole 40 shown in FIG. 1 is manufactured will be described as an example.

FIG. 9A shows an etching process for forming a fitting portion 121 by anisotropically etching the silicon substrate 120 from above and below to form holes. Figure 9
FIG. 9B shows a fitting portion 1 for the chip obtained in FIG.
21 shows a film forming step of oxidizing the periphery of 21 to form an oxide film 122 (or oxide film deposition).

FIG. 9C shows a deposition process of depositing polysilicon 123 on the chip obtained in this film forming process to form a portion corresponding to the valve 43. After this, an etching process of etching and removing the oxide film 122 is performed, and finally, a structure near the valve having a structure as shown in FIG. 9D is obtained. According to this structure, since the seal cross-sectional area can be increased, the seal performance as a closing function when an overpressure is applied can be improved.

[0053]

As described above in detail with reference to the embodiments, according to the present invention, since silicon is used as the structural material of the overpressure protection mechanism, there is no plastic deformation and the elastic characteristics are very good. Therefore, an overpressure protection mechanism with very good reproducibility can be provided. Further, according to the present invention, since it is possible to fabricate in a batch process by utilizing the fine processing technology of silicon, it is possible to fabricate a large number of overpressure protection mechanisms at the same time, which is small and inexpensive and has good reproducibility. Further, according to the present invention, since all the joint surfaces to which the excessive pressure is applied are in the compression direction, they do not peel off and are strong.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing the configuration of an embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of an overpressure protection mechanism in the embodiment shown in FIG.

FIG. 3 is a process drawing showing an outline of a manufacturing process for manufacturing the overpressure protection mechanism shown in FIG.

FIG. 4 is a vertical sectional view showing a configuration of a second embodiment of an overpressure protection mechanism formed on a substrate.

5 is a perspective view of the overpressure protection mechanism shown in FIG. 4. FIG.

FIG. 6 is a vertical cross-sectional view showing a configuration of a peripheral structure including an overpressure protection mechanism according to the present invention.

FIG. 7 is a plan view seen from AA ′ shown in FIG.

FIG. 8 is a vertical cross-sectional view showing the configuration of another peripheral structure including an overpressure protection mechanism according to the present invention.

FIG. 9 is a manufacturing process diagram illustrating the outline of the manufacturing process in the vicinity of the valve of the overpressure protection mechanism.

FIG. 10 is a vertical cross-sectional view showing the configuration of a conventional differential pressure transmitter.

[Explanation of symbols]

 1, 20, 21, 108 Body 2, 3 Pressure receiving diaphragm 4 Cover 7 Sensor capsule 8 Sensor 12 Center diaphragm 13, 14 Main body chamber 17, 44 Sealing liquid 26 Sensor part 22, 23 Overpressure protection mechanism 24, 25, 27 Vacancy 37, 63 Cantilever 39, 65 Thin portion 41, 67 Fixed portion 40, 66 Through hole 42, 68 Coupling portion 43, 69 Valve

Claims (1)

[Claims] 1. A thin portion formed by forming a recess on one side of a thick single crystal substrate, pressure guiding holes penetrating the single crystal substrate, and a thickness of the single crystal substrate. A beam provided on the other side of the single crystal substrate, which has a fixing portion provided on the wall portion, a connecting portion for connecting to the thin portion, and a valve portion provided to face the pressure guiding hole. And a second pressure applied to the other side of the single crystal substrate and obtained through the pressure guiding hole, the differential pressure being output to the sensor unit. Overpressure protection mechanism for differential pressure transmitter.