KR830002334B1 - Differential pressure detector - Google Patents

Abstract

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Description

Differential pressure detector

1 is a cross-sectional view of the overall structure of the differential pressure detector according to an embodiment of the present invention.

2 is a detailed cross-sectional view of the differential pressure detection unit.

3 is a plan view of the measuring diaphragm.

4 is a strain distribution diagram when pressure is applied to the measuring diaphragm.

5 is a view showing the effect of hydrostatic pressure when changing the diameter of the support member to the diameter of the glass washer.

6 is a detailed cross-sectional view of the differential pressure detection unit according to another embodiment.

Fig. 7 shows the piezoelectric resistance coefficient on the {110} plane.

8 shows the piezoelectric resistance coefficient in the {211} plane;

The present invention relates to a differential pressure detector for detecting the pressure of a difference between a high pressure fluid and a low pressure fluid by converting it into an electrical signal using a measuring diaphragm of a semiconductor.

Measuring diaphragm of semiconductors such as Si, which are used for differential pressure detection, having a thick outer periphery and a central part as shown in US Pat. The diaphragm in which the gauge resistance was installed by the diffusion method or the ion plantation method is known. This measuring diaphragm has an advantage that roughly the same characteristics can be obtained even if the pressure application direction (gauge side or the opposite side) is different.

However, although the gauge resistance is insulated by the PN junction with respect to the measuring diaphragm of Si, the insulation resistance of the PN junction is relatively small. For this reason, it is very difficult to prevent electrical disturbances on the gauge resistance from the outside. In the above-mentioned U.S. Patent No. 4,135,408, the configuration in which the measurement diaphragm of Si is electrically insulated is not employed. Therefore, in such a configuration, the gauge resistance is disturbed unless the differential pressure detection conductor is electrically insulated. You can't prevent it from being affected.

For this reason, when only a measuring diaphragm is insulated, insulation is easy, and it was examined to attach a measuring diaphragm to the support member of glass which has a thermal expansion coefficient close to a measuring diaphragm. However, in the differential pressure detector, a high line pressure (hydrostatic pressure) of about 100 kg / cm ^{2 is applied} to both sides of the measuring diaphragm, and a small differential pressure of about 0.1 kg / cm ² needs to be measured therebetween. Under these conditions, when the differential pressure detector having the above-described configuration was used, the measuring diaphragm and glass were deformed under a constant compressive force due to a high hydrostatic pressure, and an output by the hydrostatic pressure occurred, resulting in a measurement error. On examination of this, it was found that the measuring diaphragm was composed of Si and had a Young's modulus different from that of glass, and the difference in the Young's modulus was due to the difference in the amount of deformation between the measuring diaphragm and the glass.

Accordingly, an object of the present invention is to provide a differential pressure detector in which only the measuring diaphragm is electrically insulated from the differential pressure detection base body, and which is not influenced by the hydrostatic pressure.

The present invention allows the measurement diaphragm of a semiconductor such as Si to be attached to the differential pressure detecting base body by a first support member made of glass and a second support member made of metal. The measuring diaphragm is made thick in the outer periphery and the center, and the gauge resistance is provided in the thin part. As the first supporting member of glass, one having a thermal expansion coefficient close to that of Si such as borosilicate glass is used. As the second supporting member of the metal, one having a thermal expansion coefficient and a Young's modulus, such as Fe-Ni or Fe-Ni-Co alloy, close to that of Si is used. Therefore, the measuring diaphragm, glass, and glass and metal can also be bonded by Anodic Bonding.

1 is an overall structural sectional view of the differential pressure detector, and the magnetic pressure detector is composed of a hydraulic pressure section 10 and a differential pressure detection section 12. As shown in FIG. The hydraulic subsidiary body 14 welds and secures around the high pressure side hydraulic diaphragm 16 and the low compression hydraulic diaphragm 18 of stainless steel (monel, Hastelloy, tantalum, etc.) on both sides thereof. The high pressure side hydraulic chamber 20 and the low pressure hydraulic chamber 22 are formed between the hydraulic body 14. The center diaphragm 24 made of stainless steel with high stiffness is fixed at the center of the hydraulic part body 14 by the high pressure side and the low pressure side pressure diaphragms 16 and 18. The high pressure side containment chamber 26 and the low pressure side containment chamber 28 are formed between 14 and 14. The high pressure side pressure chamber 20 and the high pressure side isolation chamber 26 have a pressure path 32 having an aperture 30, and the low pressure side pressure chamber 22 and the low pressure side isolation chamber 28 are pressure paths. Communication through 34). In the pressure receiving portion 14, the high pressure side isolation chamber 26 and the low pressure side isolation chamber 28 communicate with the differential pressure detection unit, respectively, and the pressure paths 36 and 38 are provided, and the hydraulic pressure unit 10 and the differential pressure detection unit ( 12) There are provided openings 40 and 42 for incompressible sealing liquids, such as silicone oil, which are enclosed in the chamber. In addition, the high pressure side seal diaphragm 16 and both sides of the hydraulic part body 14 are provided. A high pressure side flange 46 having a high pressure fluid inlet 44 to cover the low pressure side seal diaphragm 18, and a low pressure side flange 50 having a low pressure fluid inlet 48 are provided near the inner ear. 52 and a nut 54 are fixed to each other.

The differential pressure detecting section 12 is composed of n-type single crystal Si of (110) plane in the center of the diaphragm 56, and the degree of confirmation 56 is the center angle at the center thereof as shown in FIGS. A thin portion 62 having a thick portion of the fixing portion 60 in the circumference 58 and the circumference and causing deformation in an annular shape is formed. The thickness of the central rigid body 58 is formed thinner than the fixing part 60, and the clearance gap is formed between the glass washers 66. As shown in FIG. In the portion 62 causing the thin deformation, the P-type gauge resistor 64 is formed by a plurality of diffusion methods or ion implantation methods in connection with the radial direction of the <111> axial direction where the maximum sensitivity is obtained. The measuring diaphragm 56 is formed by forming a gauge resistor 64 on one side and then machining the other side by machining or etching. The positions of the gauge resistors 64 are two near the outer periphery 60 and two near the central coil 58. These resistors are woven with a Wheatstone bridge and are differentially formed. To get the output. The output of the gauge resistor 64 is taken out by the aluminum wiring 65. At this time, the aluminum wiring of the gauge resistance provided in the vicinity of the center rigid body 58 is once attracted to the center rigid body, and reaches the outer periphery 60 after passing over the part causing the deformation at the gauge resistance position. That is, the aluminum wiring is also provided on the surface of the portion 62 causing deformation, but since the aluminum wiring is provided at a position away from the gauge resistance, the influence on the gauge resistance can be eliminated.

The measuring diaphragm 56 is a stainless steel differential pressure through two support members, a disk-shaped glass washer 66 having a pressure path 67 and a cylindrical metal retaining chain 68 having a pressure path 69. It is installed to protrude from the detection unit body 70. The glass washer 66 is made of a material having roughly the same material as the thermal window coefficient of Si (3.125 × 10 ⁻⁶ / ° C.), and the coefficient of thermal expansion and Young's modulus (1.732 × 10 ⁴ kg / mm ² ) of the holding metal fitting (68) Si. ), Roughly the same material on both sides is used. Specifically, the glass washer 66 is borosilicate glass (coefficient of thermal expansion 3.18 × 10 ⁻⁶ / ° C., Young's modulus 6.68 × 10 ³ kg / mm ² ), and the retaining bracket (68) is iron-nickel (Ni, 40%). (Coefficient of thermal expansion 3.6 × 10 ^-6 / ℃, Young's modulus 1.57 × 10 ⁴ kg / mm ² ) Alloy or iron-nickel-cobalt alloy (Ni 30%, Co, 17%) (Coefficient of thermal expansion 5.4 × 10 ^-6 / ℃, Young's modulus is 1.25 × 10 ⁴ kg / mm ² ). The measuring diaphragm 56, the glass washer 66, the glass washer 66, and the glass fitting 68 are joined by the anodic bonding method, and the retaining fitting 68 and the differential pressure detecting part main body 70 are each joined by arc welding. . The differential pressure detecting unit body 70 is provided with a print engine 72 made of a donut-shaped ceramic, and the print engine 72 and the measuring diaphragm 56 are configured to be roughly coplanar. The printed circuit board 72 is held by soldering to a conductor 76 passing through a plurality of through-holes 74 provided in the central axial direction along the same circumference of the differential pressure detecting portion main body. It is supported by the mechanical seal 78 provided in the conductor 76 through-hole 74. As shown in FIG. The gauge resistor 64 of the printed circuit board 72 and the measuring diaphragm 56 are brought into contact with the conductor 80, and the conductor 76 supported by the mechanical seal 78 is connected to the outer lead conductor 82. Connected. The hinge fitting 88 having the pressure paths 84 and 86 is welded and fixed to the hydraulic pressure portion 14, and the differential pressure detecting portion main body 70 is welded and fixed to the hinge fitting 88. The plate 90 is welded and fixed to the differential pressure detection unit body 70 so as to communicate the pressure path 86 and the pressure path of the holding metal fitting 68, and a printed circuit board between the measurement diaphragm 56 and the pressure path 84. A protective cover 92 of 72 is provided. The differential pressure detecting portion main body 70 is annealed when the mechanical seal 78 is applied, and the corrosion resistance of the differential pressure detecting portion main body 70 is lowered. ) Is installed. The amplification part (not shown) is connected to the upper part of the differential pressure detection part, but the amplification sub-body case 96 is fixed by the bolt 98 to the coupling fitting 88.

The volume of the high pressure side hydraulic chamber 20 and the high pressure side isolation chamber 26 or the low pressure side hydraulic chamber 22 and the low pressure side isolation chamber 28 is formed so that the isolation chamber side becomes large. That is, even if the high pressure side or the low pressure side diaphragms 16 and 18 seat on the hydraulic part body 14 by the overload pressure, the center diaphragm 24 does not sit on the hydraulic part body 14. have. As a result, since the overload pressure does not act on the measuring diaphragm 56, the characteristic deterioration damage of the measuring diaphragm 56 can be prevented.

In addition, when a high pressure fluid, such as a process fluid, is delivered from the high pressure fluid inlet 44 of the high pressure side flange 46, the pressure of the high pressure fluid is the ball bar side diaphragm 16, the pressure furnace 32, and the high pressure side containment chamber ( 26) acts on one side of the measuring diaphragm 56 through the pressure paths 36, 84. Similarly, when the low pressure fluid is also delivered from the low pressure fluid inlet 48 of the low pressure side flange 50, the pressure of the low pressure fluid is controlled by the low pressure side diaphragm 18, the pressure path 34, and the low pressure side isolation chamber 28. It acts on the other side of the measuring diaphragm 56 via the pressure paths 38, 86, 69, 67. As a result, the portion 62 causing the deformation of the measuring diaphragm 56 is bent in response to the pressure difference, whereby the resistance value of the gauge resistor 64 changes. This resistance change reaches the amplifier through the conductor 80, the printed circuit board 72, the conductors 76, and 82 and displays the pressure difference.

In FIG. 4, when pressure P is applied from the direction of the arrow, deformation as shown in the figure occurs on the surface of the portion 62 causing the deformation of the measuring diaphragm 56. The gauge resistors 64A, 64B, 64C, and 64D placed near the positions representing the maximum strains ε _m and -ε _m depend on the piezo-resistance effect, and 64B and 64D indicate tensile strain. The resistance value increases with 64A and 64C, and the resistance value decreases with compression deformation. Therefore, the output voltage corresponding to pressure is taken out differentially in the Wheatstone bridge which consists of these gauge resistors.

Next, when hydrostatic pressure is applied to the entire differential pressure detector, the Young's modulus of the measuring diaphragm 56 and the glass washer 66 are different, and therefore, the portion 62 causing deformation of the measuring diaphragm 56 is caused by joining with a member having different Young's modulus. In the part 62 which causes deformation of the measuring diaphragm 56 due to the deformability, the deformable component due to the joining of the member having different Young's modulus is generated. However, since the Young's modulus of the holding metal fitting 68 made of Fe-Ni is close to the Young's modulus of the measuring diaphragm 56 made of Si, the deformation of the glass washer 66 can be alleviated and the generation of the output voltage due to the hydrostatic pressure can be suppressed. have.

5 shows the influence of the hydrostatic pressure when the plate thickness of the glass washer 66 is used as a parameter and the diameter af of the retaining metal fitting 68 made of Fe-Ni with respect to the diameter ag of the glass washer 66 is changed. It is shown. T ₁ is one-half times the thickness of the sheet thickness measuring die application of a glass-washer (66), T ₂ is polished, T ₃ is doubled, T ₄ is the case of three times. As is apparent from the figure, in order to eliminate the influence of the hydrostatic pressure, it can be seen that as the plate thickness of the glass washer 66 increases, the diameter af of the retaining metal fitting 68 needs to be reduced. Moreover, when the plate | board thickness of the glass washer 66 becomes three times or more of the plate | board thickness of the measuring diaphragm 56, even if the diameter of the holding bracket 66 is made small, the influence by hydrostatic pressure cannot be eliminated. Therefore, in order to eliminate the influence of the hydrostatic pressure, the plate thickness of the glass washer 66 should be 3 times or less the plate thickness of the measuring diaphragm. Moreover, as the plate thickness of the glass washer 66 becomes smaller, the diameter of the retaining metal fitting 68 becomes larger. It needs to be selected by value.

FIG. 6 shows that the glass washer 66 is thinned (about tens to hundreds of micrometers) based on the result of FIG. 5, and one end portion of the retaining bracket 68 is formed as roughly as the elapse of the measuring diaphragm. . This section and the Young's modulus of the collecting member 68 are larger than the Young's modulus of the glass and are close to that of Si, so when the hydrostatic pressure is applied to the whole, the glass is stretched on both sides of the glass, and the measuring diaphragm 56 is based on the difference in Young's modulus. This one-way deformation is reduced. For this reason, the differential pressure detector of the present structure is no longer affected by the static pressure.

According to the experiments of the inventors, it was found that the effect of the thickness of the metal serving as the lining portion of the glass material was greater than at least twice the glass thickness.

Fig. 6 shows the piezoelectric resistance coefficient πl (piezoelectric resistance coefficient when the current direction and the stress direction of the element are parallel), πt (perpendicular) In this case, the effect of the <111> axis described above in this drawing is apparent. FIG. 7 shows a P-type piezoresistive element on the {211} plane as an example of the distribution of pi and pi on another peak surface. In the case of the {211} plane, the <111> axis is also valid as the {110} plane. In this structure, the output voltage is large, and since the deformation can be given in parallel to the gauge resistance, the characteristic is almost dominated by the characteristic with the longitudinal piezo resistance.

However, according to our experimental results, it is known that the temperature change of the output during constant current excitation is smaller in the longitudinal piezo resistance effect than in the horizontal piezo resistance effect. Moreover, although the magnitude | size of the nonlinear error in a deformation | transformation change is changed with respect to temperature, the amount of change also becomes smaller than using a transverse piezo resistance effect by using the longitudinal piezo resistance effect.

From the above, the measuring diaphragm of the present structure can produce a large output because the bridge can be formed by a gauge resistor in which the principal component is disposed in the radial direction, and the advantage of reducing the temperature dependency of both the span and the nonlinear error can be obtained. There is this.

According to the present invention as described above, since only the measuring diaphragm can be electrically insulated from the differential pressure detector main body, the insulation is simplified, and further, a differential pressure detector that is not affected by the hydrostatic pressure can be obtained.

Claims (1)

On the outer periphery of the differential pressure detecting unit main body 70 into which two fluids with different pressures are introduced, and on the outer periphery of the portion 62, which causes a thin deformation, in which the gauge resistor 64 is formed on the outer periphery of the thick portion; Between the holding diaphragm 56 of the semiconductor having the thickened portion 60 and the holding member bonded to the fixing portion 60 of the measuring diaphragm 56, the holding support, and the differential pressure detecting portion main body 70; A pressure differential detector (32) (34) provided with a fluid formed by communicating between a metal support provided between said holding support and said holding support.

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