JPH0783778A - Differential pressure measuring device - Google Patents

Abstract

PURPOSE:To prevent the welding inferiority of center diaphragms by moving a seal liquid through the communication hole of the second center diaphragm having a smaller diameter fixed to a first center diaphragm. CONSTITUTION:When pressure is applied on the high pressure side, the center part of a first center diaphragm 21 is prevented from deformation by the second center diaphragm 24 attached to the first center diaphragm 21 and deformation is mainly generated in the outer peripheral part of the diaphragm 21 to suppress the quantity of the deformation of the diaphragm 21 low. When pressure is applied on a low pressure side, a seal liquid 102 is moved through the communication hole 26 of the diaphragm 24 and the overlapped part of the diaphragms 21, 24 is deformed to obtain the large quantity of displacement. Therefore, the volumetric change quantity based on the deformation of the diaphragms 21, 24 due to the pressures on the high and low pressure sides is made high on the high pressure side and low on the low pressure side in order to obtain definite displacement. As a result, since only one thin diaphragm 21 is held between housings to be welded and fixed, welding and fixing become easy and welding inferiority can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can protect the sensor main body from instantaneous overpressure, and prevent the occurrence of welding defects in the housing of the center diaphragm.
The present invention relates to a differential pressure measuring device capable of reducing hysteresis.

[0002]

2. Description of the Related Art FIG. 5 is a structural explanatory view of a conventional example which has been generally used, for example, Japanese Patent Laid-Open No. 55-1221.
No. 26 is shown. This structure shows a structure of a differential pressure measuring device that has different overpressure protection characteristics on the high-pressure side and the low-pressure side because the pressure resistance strength varies depending on the direction of the pressure applied to the semiconductor diaphragm.

In the figure, a high pressure side flange 2 and a low pressure side flange 3 are fixed to both sides of a housing 1 by welding or the like, and a pressure P to be measured on both flanges 2 and 3 is measured.
Inlet 4 for high-pressure fluid _H and inlet 5 for low-pressure fluid P _L
Is provided.

A pressure measuring chamber 6 is formed in the housing 1, and a pressure receiving diaphragm 7 and a silicon diaphragm 8 are provided in the pressure measuring chamber 6. The pressure receiving diaphragm 7 and the silicon diaphragm 8 are separately fixed to the wall of the pressure measuring chamber 6, and the pressure measuring chamber 6 is divided into two by both the pressure receiving diaphragm 7 and the silicon diaphragm 8.

The pressure receiving diaphragm 7 is a diaphragm 7A.
And a diaphragm 7B having a hole 70. Of course, the number of diaphragms may be three or more, and the diameter of the hole is preferably small, and the number is not limited. It is advantageous in processing that the hole 70 is formed on a flat surface. The gap between the diaphragms 7A and 7B should be as small as possible so that when the differential pressure ΔP (= pressure P _H -pressure P _L ) acts from the diaphragm 7A side, it is immediately received by the two diaphragms 7A and 7B. .

Further, the diaphragms 7A and 7B are formed in a similar shape so that the space formed between both diaphragms is reduced. The walls 7A and 6B of the pressure measuring chamber 6 facing the diaphragms 7A and 7B have diaphragms 7A and 7B, respectively.
A back plate similar in shape to B is formed. The back plates 6A and 6B are effective in reducing the volume of the pressure measuring chamber 6.

The silicon diaphragm 8 is entirely formed of a single crystal silicon substrate. Impurities such as boron are selectively diffused on one surface of the silicon substrate to form four strain gauges 80, and the other surface is machined and etched to form a diaphragm having an overall concave shape. In the 4 strain gauge 80, the silicon diaphragm 8 has a differential pressure Δ.
When P is bent and deflected, two are pulled and two are compressed. These are connected to a Wheatstone bridge circuit, and a resistance change is detected as a change in the differential pressure ΔP.

The housing 1 is generally made of stainless steel, and has a considerable difference in coefficient of thermal expansion from the silicon diaphragm 8. Therefore, between the housing 1 and the silicon diaphragm 8, a hollow support 9 having a thermal expansion coefficient substantially the same as that of silicon is provided so that the silicon diaphragm 8 projects into the pressure measuring chamber 6. If a heat-resistant glass such as borokei glass is used for the support 9, the silicon diaphragm 8, the support 9 and the housing 1 can be bonded by the three-anodic bonding method, and firm bonding can be achieved without slippage of the bonding surface between the respective members.

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, and the separating diaphragm 1 is provided.
A back plate having a shape similar to that of the diaphragms 12 and 13 is formed on the walls 10A and 11A of the housing 1 which are opposed to the diaphragms 2 and 13.

The space defined by the 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. Then, filled liquid 101, 102 such as silicone oil is filled between the diaphragms 12, 13, and the filled liquid reaches the upper and lower surfaces of the silicon diaphragm 8 through the communication holes 16, 17. Although 102 is divided into two by the pressure receiving diaphragm 7 and the silicon diaphragm 8, it is taken into consideration that the amounts are substantially equal.

The amount of the enclosed liquid 101, 102 is preferably as small as possible in order to reduce the influence of the ambient temperature change as much as possible, but the back plates 6A, 6B, 10A, 11A reduce the amount of the enclosed liquid. Is useful to.

The stiffness of the diaphragms 12 and 13 is preferably as small as possible in terms of responsiveness to pressure and absorption of thermal expansion of the enclosed liquid. Between the pressure receiving diaphragm 7 and the diaphragms 12 and 13, the pressure receiving diaphragm 7 is provided between the back plates 6A and 6B before the diaphragms 12 and 13 come into contact with the back plates 10A and 11A.
Make sure that the relationship does not come into contact with.

In such a differential pressure converter, the inlets 4, 5
When the fluid to be measured having the pressure P _{H and} the fluid to be measured having the pressure P _L are introduced into the housing 1 from the above, the pressures P _H and P _L of the fluid are respectively filled via the diaphragms 12 and 13.
1, 102, and the silicon diaphragm 8 detects the differential pressure ΔP = | P _H −P _L | between the two fluids.

At this time, if P _H > P _L , the diaphragm 12 and the pressure receiving diaphragm 7 move to the right in the figure. Then, the volume change amount of the left half of the pressure measurement chamber 6 is set to Δ
If V _H , ΔP _H = P _H −P _L , then the relationship between ΔP _H and ΔV _H is as shown in FIG.

[0015] That is, [Delta] V _H also increases with increasing [Delta] P _H, a point _{(ΔP 1, ΔV 1) ΔV} H does not increase the boundary. This point a is the time when the diaphragm diaphragm 12 comes into contact with the back plate 10a, and since the diaphragm diaphragm 12 does not move to the right any more, ΔV _H does not increase, and the silicon diaphragm 8 also has ΔP ₁ The above pressure will not be applied.

Similarly, if P _L > P _H , ΔP _L = P _L −P _H , and the volume change amount of the right half of the pressure measuring chamber 6 is ΔV _L , Δ
The relationship between P _L and ΔV _L is shown in FIG. Point b (ΔP ₂ , Δ
In V ₂ ), the diaphragm 13 has a back plate 11A.
Is the point of contact with.

As can be seen from FIG. 5, a large differential pressure ΔP ₁ ,
Alternatively, a small differential pressure ΔP ₂ can be applied to the weaker one, and a differential pressure in a wide range of ΔP _{1 to} ΔP ₂ with improved input / output characteristics can be detected. Further, since the pressure of ΔP ₁ or ΔP ₂ or more is not applied to the silicon diaphragm, the differential pressure measurement can be performed regardless of the pressure of the measurement fluid.

[0018]

However, in such an apparatus, since the measured differential pressure is large and a single center diaphragm cannot provide sufficient rigidity, the hole 70 is provided in addition to the diaphragm 7A. The one diaphragm 7B which it has is used together.

The two diaphragms 7A and 7B are overlapped with each other and the outer peripheral portion is sandwiched between the housings 1 and fixed by welding. In a model with a high measured differential pressure, the thickness of the diaphragm 7B becomes thicker, and when combined with the diaphragm 7A, it becomes several mm.

Therefore, the following problems occur. (1) Two diaphragms 7A and 7B having a size of several mm are sandwiched by the housing 1 and welded and fixed together A. In order to ensure this welding fixation, the weld penetration depth needs to be a certain level or more. For this deep welding, for example, an electron beam is used, but it is difficult to stably secure a welding width above a certain level, and welding defects frequently occur.

(2) The thick plate-shaped diaphragm 7A is sandwiched and fixed in the housing 1 by welding, and is displaced when a differential pressure is applied, but the stress at the fulcrum portion (point B) increases during displacement, At the time of displacement, it becomes a characteristic error factor such as hysteresis, zero drift, and input / output error.

The present invention solves this problem. An object of the present invention is to provide a differential pressure measuring device capable of protecting the sensor main body portion against a momentary excessive pressure, preventing occurrence of welding failure in the housing of the center diaphragm, and reducing hysteresis. It is in.

[0023]

In order to achieve this object, the present invention provides a housing filled with an enclosed liquid, a pair of diaphragms provided on both sides of the housing, and the diaphragm. In a differential pressure measuring device comprising a displacement limiting means provided so that the diaphragm is not displaced toward the housing side by a certain amount or more, and a silicon diaphragm having a pressure-electric conversion element provided in the housing,
A first center diaphragm provided in the housing along with the silicon diaphragm so as to be divided into a high-pressure side chamber and a low-pressure side chamber, and an outer peripheral portion provided in the low-pressure side chamber and fixed to the first center diaphragm. A second center diaphragm having a diameter smaller than that of the center diaphragm and not contacting the chamber wall of the low-pressure side chamber at the time of measurement, and a communication hole penetrating the second center diaphragm and capable of moving the enclosed liquid are provided. A differential pressure measuring device characterized by the above.

[0024]

In the above structure, when pressure is applied from the high pressure side, the first center diaphragm is restrained by the second center diaphragm, and the center portion of the first center diaphragm is prevented from being deformed. Therefore, the deformation of the first center diaphragm is mainly caused by the deformation of the outer peripheral portion than the portion where the second center diaphragm is attached, and the displacement amount can be suppressed to be small.

When the pressure is applied from the low pressure side, the enclosed liquid moves through the communication hole of the second center diaphragm, the overlapping portion of the first center diaphragm and the second center diaphragm is deformed, and the pressure from the high pressure side is changed. A large displacement amount can be obtained as compared with the case where is applied.

Therefore, the amount of change in the volume due to the deformation of the center diaphragm due to the pressure on the high pressure side and the pressure on the low pressure side, the pressure for obtaining a constant displacement (the pressure capable of protecting against excessive pressure) is high on the high pressure side, and on the low pressure side. It can be kept low. Hereinafter, detailed description will be given based on examples.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of the essential structure of an embodiment of the present invention. In the figure, the same symbols as those in FIG. 5 represent the same functions. Only parts different from FIG. 5 will be described below. 21 is
The first center diaphragm is provided in the housing 1 along with the silicon diaphragm 8 so as to be divided into a high pressure side chamber 22 and a low pressure side chamber 23.

Reference numeral 24 denotes a chamber wall of the low pressure side chamber 23, which is provided in the low pressure side chamber 23, has an outer peripheral portion welded and fixed to the first center diaphragm 21, and has a diameter smaller than that of the first center diaphragm 21. The second center diaphragm is not in contact with the back plate 6B. Reference numeral 26 is a communication hole which is provided so as to penetrate the second center diaphragm 24 and through which the enclosed liquid 102 can move.

In the above structure, when pressure is applied from the high pressure side, as shown in FIG. 2, the first center diaphragm 21 is constrained by the second center diaphragm 24, and the central portion of the first center diaphragm 21 is Deformation is hindered. Therefore, the deformation of the first center diaphragm 21 is mainly due to the deformation of the outer peripheral portion rather than the portion where the second center diaphragm 24 is attached, and the displacement amount can be suppressed to be small.

When the pressure is applied from the low pressure side, as shown in FIG. 3, the communication hole 2 of the second center diaphragm 24 is formed.
The filled liquid 102 moves through 5, and the overlapping portion of the first center diaphragm 21 with the second center diaphragm 24 is deformed, so that a large displacement amount can be obtained as compared with the case where pressure is applied from the high pressure side.

Therefore, the amount of change in the volume due to the deformation of the center diaphragms 21 and 24 due to the pressure on the high pressure side and the pressure on the low pressure side is, as shown in FIG. 4, a pressure for obtaining a constant displacement (pressure capable of protecting against excessive pressure). Is as high as ΔP ₁ on the high pressure side,
It can be kept as low as ΔP ₂ on the low voltage side. In FIG. 4, ΔV ₁ = ΔV ₂ .

As a result, (1) the overpressure protection on the high pressure side and the low pressure side can be performed in the same manner as in the conventional example. (2) Unlike the conventional case, the fixed part of the center diaphragm is configured such that only one thin center diaphragm 21 is sandwiched in the housing 1 and fixed by welding. Does not occur, the welding reliability is high, and the yield is improved, so that the manufacturing cost can be reduced.

(3) Since the deformation of the center diaphragm 21 at the fulcrum portion to which the center diaphragm 21 is fixed is reduced, the hysteresis caused by the deformation friction as in the conventional example is reduced and the hysteresis characteristic is greatly improved. . In addition, in the above-mentioned embodiment, in order to make the explanation of the operation easy to understand, the explanation has been made with respect to the flat plate-shaped diaphragm, but the present invention is not limited to this, and for example, a corrugated corrugated diaphragm may be used. I wish I had it.

[0034]

As described above, according to the present invention, the housing filled with the filled liquid, the pair of diaphragms provided on both sides of the housing, and the diaphragms having a certain number or more on the housing side. In a differential pressure measuring device comprising a displacement limiting means provided so as not to be displaced to a high pressure side and a silicon diaphragm having a pressure-electricity conversion element provided in the housing, a high pressure side chamber and a low pressure chamber together with the silicon diaphragm in the housing A first center diaphragm provided so as to divide into a side chamber and an outer peripheral portion provided in the low pressure side chamber and fixed to the first center diaphragm and having a diameter smaller than that of the first center diaphragm. A second center diaphragm that does not contact the chamber wall of the side chamber, and the second center diaphragm Filled liquid provided through constituted the differential pressure measuring apparatus characterized by comprising a movable passage.

As a result, (1) the overpressure protection on the high pressure side and the low pressure side can be performed in the same manner as in the conventional example. (2) Unlike the conventional case, the fixed part of the center diaphragm is configured such that only one thin center diaphragm 21 is sandwiched in the housing 1 and fixed by welding. Does not occur, the welding reliability is high, and the yield is improved, so that the manufacturing cost can be reduced.

(3) Since the deformation of the center diaphragm 21 at the fulcrum portion to which the center diaphragm 21 is fixed is small, the characteristics such as hysteresis, zero drift, input / output error, etc. due to deformation friction as in the conventional example are large. Will be improved.

Therefore, according to the present invention, it is possible to protect the sensor main body portion against a momentary excessive pressure and prevent the welding failure of the center diaphragm to the housing.
Further, it is possible to realize a differential pressure measuring device that can reduce hysteresis.

[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 operation explanatory diagram of FIG.

FIG. 3 is an operation explanatory diagram of FIG. 1.

FIG. 4 is an operation explanatory diagram of FIG. 1.

FIG. 5 is an explanatory diagram of a configuration of a conventional example that is generally used in the past.

FIG. 6 is an operation explanatory diagram of FIG. 5;

[Explanation of Codes] 1 ... Housing 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 8 ... Silicon diaphragm 9 ... Support Body 10 ... Pressure introducing chamber 10A ... Back plate 11 ... Pressure introducing chamber 11A ... Back plate 12 ... Separating diaphragm 13 ... Separating diaphragm 14 ... Communication hole 15 ... Communication hole 16 ... Communication hole 17 ... Communication hole 21 ... 1st center diaphragm 22 ... High pressure side chamber 23 ... Low pressure side chamber 24 ... Second center diaphragm 25 ... Welding fixing 26 ... Communication hole 80 ... Strain gauge

Claims (1)

[Claims] 1. A housing in which a filled liquid is filled,
A pair of liquid diaphragms provided on both sides of the housing, a displacement limiting means provided so that the liquid diaphragms are not displaced toward the housing side by a certain amount or more, and a pressure-electricity conversion element provided in the housing. In a differential pressure measuring device including a silicon diaphragm, a first center diaphragm provided in the housing so as to be divided into a high pressure side chamber and a low pressure side chamber together with the silicon diaphragm, and an outer peripheral portion provided in the low pressure side chamber. Is fixed to the first center diaphragm, has a diameter smaller than that of the first center diaphragm, and does not come into contact with the chamber wall of the low-pressure side chamber at the time of measurement, and is provided so as to penetrate the second center diaphragm. A differential pressure measuring device having a communication hole through which the filled liquid can move. .