JPH055666A - Differential pressure measuring device - Google Patents

Abstract

PURPOSE:To obtain the differential pressure measuring device enhanced in hysteresis and durability. CONSTITUTION:A sealing liquid type differential pressure measuring device is equipped with a housing consisting of a neck part 1A and a pressure receiving part 1B, the pressure-electric signal converter element provided to the neck part 1A, the center diaphragm 7 provided to the pressure receiving part 1B, the liquid separating diaphragms 12, 13 provided to both side surfaces of the pressure receiving part 1B and the back plates 6A, 6B provided to the pressure receiving part 1B in opposed relation to the liquid separating diaphragms 12, 13. The back plates 6A, 6B formed so that the reference positions of the liquid separating diaphragms 12, 13 at room temp. become a recessed state on the side of the center diaphragm 7 from the natural shapes of the liquid separating diaphragms 12, 13 are mounted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential pressure measuring device in which stress generated in a diaphragm of a diaphragm at a high temperature and overpressure is reduced, and hysteresis and durability are improved.

[0002]

2. Description of the Related Art FIG. 3 is an explanatory view of the configuration of a conventional example which has been generally used, for example, in the actual Japanese Utility Model Laid-Open No. 60-1816.
No. 42. In the figure, reference numeral 1 denotes a housing, which has a cylindrical neck portion 1A and an end outer peripheral edge portion 1C of the neck portion 1A.
In, the pressure receiving portion 1B is connected by welding and has a block shape. The high-pressure side flange 2 and the low-pressure side flange 3 are fixed to both sides of the housing 1 by welding or the like. The high-pressure fluid inlet port 4 of the pressure PH to be measured and the low-pressure fluid pressure PL An introduction port 5 is provided.

A pressure measuring chamber 6 is formed in the housing 1, and a center diaphragm 7 and a silicon diaphragm 8 are provided in the pressure measuring chamber 6. The center diaphragm 7 and the silicon diaphragm 8 are separately fixed to the wall of the pressure measuring chamber 6, and the center diaphragm 7 and the silicon diaphragm 8 both divide the pressure measuring chamber 6 into two parts. Back plates 6A and 6B are formed on the wall of the pressure measuring chamber 6 facing the center diaphragm 7.

A peripheral portion of the center diaphragm 7 is welded to the housing 1. The silicon diaphragm 8 is entirely formed of a single crystal silicon substrate. Selectively diffuse impurities such as boron on one surface of the silicon substrate 4
Then, a strain gauge 80 is formed, and the other surface is machined and etched to form a diaphragm having an overall concave shape. When the silicon diaphragm 8 bends under the pressure difference ΔP, two strain gages 80 pull two
Are connected to a Wheatstone bridge circuit, and the resistance change is a differential pressure ΔP.
Is detected as a change in.

Reference numeral 81 is a lead whose one end is attached to the strain gauge 80. Reference numeral 82 is a hermetic terminal to which the other end of the lead 81 is connected. The support 9 has a hermetic terminal,
A silicon diaphragm 8 is adhesively fixed to the end surface of the support 9 on the pressure measurement chamber 6 side by a method such as low-melting glass connection.
Pressure introducing chambers 10 and 11 are formed between the housing 1 and the high pressure side flange 2 and the low pressure side flange 3.

Separating diaphragms 12 and 13 are provided in the pressure introducing chambers 10 and 11, respectively.
A back plate having a shape similar to that of the diaphragms 12 and 13 is formed on the walls 10 A and 11 A of the housing 1 facing the housing 13. The space formed by the liquid diaphragms 12 and 13 and the back plates 10A and 11A and the pressure measuring chamber 6 are in communication with each other through communication holes 14 and 15.

Filling liquid 101, 102 such as silicone oil is filled between the diaphragms 12, 13.
The filled liquid 101, 1 reaches the upper and lower surfaces of the silicon diaphragm 8 through the communication holes 16, 17.
02 is a center diaphragm 7 and a silicon diaphragm 8
It is divided into two by and, but the amount is considered to be almost equal.

In the above structure, when pressure is applied from the high pressure side, the pressure acting on the diaphragm 12 is
It is transmitted to the silicon diaphragm 8 by the enclosed liquid 101. On the other hand, when pressure acts from the low pressure side, the pressure acting on the diaphragm diaphragm 13 is transmitted to the silicon diaphragm 8 by the enclosed liquid 102.

As a result, the silicon diaphragm 8 is distorted according to the pressure difference between the high pressure side and the low pressure side, and the strain amount is electrically taken out by the strain gauge 80, and the differential pressure is measured. ..

[0010]

In such an apparatus, a principle configuration explanatory view is shown in FIG. 4 and a principle explanatory view is shown in FIG. Here, VB1 is the amount of the enclosed liquid between the diaphragm and the back plate, Vs is the amount of the enclosed liquid around the center diaphragm, and VB1 is the amount of the enclosed liquid around the sensor portion and in the communication hole. .. Here, as shown in the figure, when the liquid diaphragm 12 receives the pressure P, the pressure P is transmitted to the center diaphragm 7 and the silicon diaphragm 8 via the filled liquid 101, and the center diaphragm 7 is
It deforms convexly on the right side of the figure. Therefore, VB1 on the left side of the figure decreases and VB1 on the right side of the figure increases by the excluded volume of the center diaphragm 7. When the pressure P reaches a preset pressure P1, the diaphragm diaphragm 12 comes into close contact with the back plate 10A, and no further pressure is transmitted to the silicon diaphragm 8, and the sensor portion is protected.
In this case, the initial positions of the diaphragms 12 and 13 are
It is the position of the shape of the diaphragm in its natural state. The following relationships are established at room temperature. (1) Excluded Volume of Left Separating Diaphragm = Excluded Volume of Center Diaphragm = Excluded Volume of Right Diaphragm Diaphragm (2) Maximum value of excluded volume of each diaphragm = VB1 Now, when the temperature rises, the enclosed liquid 101, Since the expansion coefficient of 102 is generally much larger than that of metal, the filling liquid 10
The volume of 1,102 increases by the volume expansion. When the volume expansion coefficient of the enclosed liquid is α, VB1 when the temperature rises by ΔT is as follows. VB1 at T ℃ = VB1 + (VB1 + Vs + VB2) × α × ΔT (3) This is because the pressure is zero and the diaphragms 12 and 13 are already convex by (VB1 + Vs + VB2) × α × ΔT (4). Show a thing. Further, by receiving the overpressure P1, each of the diaphragms 12 and 13 eliminates the volume of VB1 at T ° C. (5). Therefore, the diaphragm diaphragm 13 on the right side of the figure is (4) +
Only (5) is convex to the right of the figure. (4) + (5) = (VB1 + Vs + VB2) × α × ΔT + VB1 at T ° C. = (VB1 + Vs + VB2) × α × ΔT + VB1 + (VB1 + Vs + VB2) × α × ΔT = VB1 + 2 (VB1 + VS2) × VB1 + VB2 + Vs2 From the above, the maximum excluded volume of the diaphragm is as follows. Separating diaphragm 13 (convex in this case) = (6) formula = VB1 + 2 (VB1 + Vs + VB2) × α × ΔT (7) Separating diaphragm 12 (concave in this case). ) = VB1 atRT (contacts the back plate 10A at VB1 atRT.) (8) Therefore, the diaphragm diaphragm 13 side (convex side) is more than the diaphragm diaphragm 12 side (concave side) 2 (VB1 + Vs + VB2) ×
Exclude a large amount of enclosed liquid by α × ΔT. FIG. 6 shows the relationship between the excluded volume of the diaphragm and the maximum stress. As the excluded volume increases, the stress increases exponentially, and as the stress increases, the diaphragm of the diaphragm deforms plastically, which appears as input / output hysteresis in the differential pressure measuring device. This hysteresis becomes the largest at the time of high temperature and pressure at which the repulsion volume becomes maximum, and the hysteresis at this time is mainly generated by the convex diaphragm. Therefore, in the conventional structure in which the reference position of the diaphragm at normal temperature is the natural shape of the diaphragm, the expansion amount of the enclosed liquid is large when the whole enclosed liquid is large, and the expansion amount at high temperature and overpressure is large. The stress of the diaphragm on the convex side increases, the hysteresis increases, and the durability decreases. In the differential pressure measuring device adopting the center diaphragm method, the amount of filled liquid is inevitably increased and the above-mentioned problems occur. Further, in a high-accuracy, for example, differential pressure measuring device having an overall error of ± 0.1%, the influence of the presence of the above-mentioned hysteresis on the overall error becomes large, and it is necessary to make the hysteresis as small as possible. The present invention is
This problem is solved.

An object of the present invention is to provide a differential pressure measuring device in which the stress generated in the diaphragm of the diaphragm at a high temperature and overpressure is reduced, and the hysteresis and durability are improved.

[0012]

To achieve this object, the present invention provides a housing comprising a neck portion and a pressure receiving portion,
A pressure-electrical signal conversion element provided on the neck portion, a center diaphragm provided on the pressure receiving portion, a liquid diaphragm provided on both side surfaces of the pressure receiving portion, and the pressure receiving surface facing the liquid diaphragm. In a sealed liquid type differential pressure measuring device having a back plate provided in the section, the reference position of the diaphragm of the diaphragm at room temperature is concave to the center diaphragm side from the natural shape of the diaphragm of diaphragm. The differential pressure measuring device is characterized by comprising the formed back plate.

[0013]

In the above structure, when pressure is applied from the high pressure side, the pressure acting on the diaphragm is transmitted to the silicon diaphragm by the enclosed liquid. On the other hand, when pressure acts from the low pressure side, the pressure acting on the diaphragm is transmitted to the silicon diaphragm by the enclosed liquid. As a result, the silicon diaphragm is distorted according to the pressure difference between the high pressure side and the low pressure side, and this strain amount is a strain gauge.
It is taken out electrically and the differential pressure is measured.

Since the back plate is formed so that the reference position of the diaphragm at room temperature is concave toward the pressure receiving portion side from the natural shape of the diaphragm, the diaphragm is separated at high temperature and overpressure. The stress generated in the diaphragm can be made smaller than in the conventional example. Hereinafter, detailed description will be given based on examples.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of the essential structure of an embodiment of the present invention.
FIG. 2 is an explanatory diagram of the principle of FIG. In the figure, the same symbols as those in FIG. 3 represent the same functions. Only parts different from FIG. 3 will be described below. The reference positions of the diaphragms 12 and 13 of the diaphragms 21 and 13 at room temperature are the diaphragms 1 and 21.
The back plate is formed so as to be concave toward the center diaphragm 7 side from the natural shapes 2 and 13. In FIG. 2, the dotted line shows the shape of the diaphragms 12 and 13 in the natural state.

In the above structure, when pressure is applied from the high pressure side, the pressure acting on the diaphragm 12 is
It is transmitted to the silicon diaphragm 8 by the enclosed liquid 101. On the other hand, when pressure acts from the low pressure side, the pressure acting on the diaphragm diaphragm 13 is transmitted to the silicon diaphragm 8 by the enclosed liquid 102. As a result, depending on the pressure difference between the high pressure side and the low pressure side, the silicon diaphragm 8
Is strained, and the strain amount is electrically taken out by the strain gauge 80, and the differential pressure is measured.

Thus, the diaphragm 1 at room temperature
Since the back plates 12 and 13 are formed such that the reference positions of 2 and 13 are recessed toward the center diaphragm side from the natural shape of the diaphragms 12 and 13, they are generated in the diaphragm at high temperature and overpressure. The applied stress can be made smaller than in the conventional example. That is, according to the equations (7) and (8), the maximum excluded volume in which the diaphragm is deformed into a convex shape is 2 (VB1 + Vs + VB2) times the excluded volume in the case of being deformed into a concave shape.
There are many α × ΔT. Therefore, in order to make the convex amount and the concave amount the same, the back plates 21 and 22 are designed so that the initial positions of the diaphragms 12 and 13 are (VB1 + Vs + VB2) × α × ΔT from the natural shape. In this case, ΔT =
Designed as 100 ° C. The displacement volume on the convexly deformed side of the diaphragm at high temperature and overpressure is VB1 at T ° C = VB1 atRT + 2 (VB1 + Vs + VB2) × α × ΔT according to equation (6), which is the diaphragm diaphragm. Since the initial position is concave, when viewed from the natural shape, only VB1 + 2 (VB1 + Vs + VB2) × α × ΔT− (VB1 + Vs + VB2) × α × ΔT = VB1 + (VB1 + Vs + VB2) × α × ΔT are excluded. The generated stress can be further reduced.

As a result, the stress generated in the diaphragms 12 and 13 at high temperature and high pressure can be reduced, so that the high temperature and overpressure hysteresis can be reduced.
And durability is improved.

In the above-mentioned embodiments, the back plates 21 and 22 are designed to have a ΔT of 100 ° C., but the invention is not limited to this. The reference position is
Center diaphragm 7 based on the natural shape of the diaphragm
It is sufficient if the back plate is formed so as to be concave on the side. This is because if the diaphragms 12 and 13 are assembled in a concave shape, the stress at the time of excessive pressure can be reduced as much as possible.

[0020]

As described above, according to the present invention, a housing including a neck portion and a pressure receiving portion, a pressure-electric signal converting element provided on the neck portion, a center diaphragm provided on the pressure receiving portion, A sealed liquid type differential pressure measuring device comprising a diaphragm diaphragm provided on both side surfaces of the pressure receiving portion and a back plate provided on the pressure receiving portion facing the diaphragm diaphragm, at room temperature. A differential pressure measuring device comprising a back plate formed such that a reference position of the diaphragm is concave toward the center diaphragm with respect to a natural shape of the diaphragm.

Since the back plate is formed such that the reference position of the diaphragm at room temperature is concave to the center diaphragm side from the natural shape of the diaphragm, the diaphragm diaphragm at high temperature and overpressure is formed. It is possible to reduce the stress generated in the case compared to the conventional example.

As a result, the stress generated in the diaphragm at high temperature and high pressure can be reduced, so that the high temperature and high pressure hysteresis can be reduced and the durability can be improved.

Therefore, according to the present invention, it is possible to realize the differential pressure measuring device in which the stress generated in the diaphragm of the diaphragm at the time of high temperature and overpressure is reduced, and the hysteresis and the durability are improved.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention.

FIG. 2 is an explanatory view of the principle of FIG.

FIG. 3 is a diagram illustrating a configuration of a conventional example that is generally used in the past.

FIG. 4 is an explanatory diagram of the principle configuration of FIG.

5 is a diagram illustrating the principle of FIG.

FIG. 6 is an operation explanatory diagram of FIG. 3;

[Explanation of symbols]

 1 ... Housing 1A ... Neck 1B ... Pressure receiving part 1C ... Welding 2 ... High pressure side flange 3 ... Low pressure side flange 4 ... Inlet port 5 ... Inlet port 6 ... Pressure measuring chamber 6A ... Back plate 6B ... Back plate 7 ... Center diaphragm 8 ... Silicon diaphragm 9 ... Support 10 ... Pressure introducing chamber 11 ... Pressure introducing chamber 12 ... Separating diaphragm 13 ... Separating diaphragm 14 ... Communication hole 15 ... Communication hole 16 ... Communication hole 17 ... Communication hole 21 ... Back prep -Tote 22 ... Back plate 80 ... Strain gauge 81 ... Lead 82 ... Hermetic terminal 101 ... Encapsulating liquid 102 ... Encapsulating liquid

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenichi Yoshioka 2-9-32 Nakamachi, Musashino-shi, Tokyo Yokogawa Electric Co., Ltd.

Claims (1)

Claim: What is claimed is: 1. A housing comprising a neck portion and a pressure receiving portion, a pressure-electric signal conversion element provided on the neck portion, a center diaphragm provided on the pressure receiving portion, and a pressure receiving portion of the pressure receiving portion. Separating diaphragms provided on both side surfaces, and a back plate provided on the pressure receiving portion so as to face the separating diaphragms.
And a back plate formed so that the reference position of the diaphragm at room temperature is concave toward the center diaphragm from the natural shape of the diaphragm. A differential pressure measuring device characterized by being provided.