JPH05142078A - Differential pressure measuring device - Google Patents

Abstract

PURPOSE:To protect a sensor body from instantaneous excessive pressure and improve an input/output characteristics in a wide measuring range by setting a center diaphragm and a leaf spring to be contact under a normal measuring range. CONSTITUTION:When excessive pressure is applied from high-pressure side, a center diaphragm 21 and a leaf spring 22 works being contact with each other up to the specified pressure more than normal measuring range, a liquid partition diaphragm 12 is fitted on a housing 1 at the specified pressure, thus preventing a silicone diaphragm 8 from being pressed by the pressure more than the specified pressure. When excessive pressure is applied from low-pressure side, the diaphragm 21 and the spring 22 works in contact with each other up to the specified pressure more than the normal measuring range, only the diaphragm 21 shifts at the specified pressure, and a liquid partition diaphragm 13 is fitted on the housing 1 at constant pressure more than the specified pressure, thus preventing the diaphragm 8 from being pressed by the pressure more than the constant pressure.

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 capable of protecting a sensor main body against momentary excessive pressure from a high pressure side and a low pressure side and having a wide measuring range and improved input / output characteristics. Is.

[0002]

2. Description of the Related Art FIG. 4 is an explanatory view of the configuration of a conventional example which has been generally used, for example, JP-A-55-12212.
No. 6 is shown. 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. The high-pressure fluid inlet 4 and the pressure P of a pressure P _H to be measured are measured on both the flanges 2 and 3. _{An L} low pressure fluid inlet 5 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 it is preferable that the total number of holes is 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, and when the differential pressure ΔP (= pressure P _H −pressure P _L ) acts from the diaphragm 7A side, it should be immediately received by the two diaphragms 7A and 7B. ..

Further, the diaphragms 7A and 7B are formed in similar shapes 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 flexed, 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 coefficient of thermal expansion difference 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 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, respectively.
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 formed by the diaphragms 12 and 13 and the back plates 10A and 11A and the pressure measuring chamber 6 are connected to each other through communication holes 14 and 15. Filling liquid 101, 102 such as silicone oil is filled between the diaphragms 12, 13, and the filling liquid reaches the upper and lower surfaces of the silicon diaphragm 8 through the communication ports 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 filled 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 filled liquid amount. Is useful for.

The stiffness of the diaphragms 12 and 13 is preferably as small as possible in terms of response to pressure and absorption of thermal expansion of the enclosed liquid. Between the pressure receiving diaphragm 7 and the liquid diaphragms 12, 13, the pressure receiving diaphragm 7 is back plate 6A, 6B before the liquid diaphragms 12, 13 contact the back plates 10A, 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 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 measuring chamber 6 is Δ
If V _H , ΔP _H = P _H −P _L , then the relationship between ΔP _H and ΔV _H is as shown in FIG.

That is, although ΔV _H also increases with the increase of ΔP _H , ΔV _H does not increase at the point a (ΔP ₁ , ΔV ₁ ). This point a is the time when the diaphragm diaphragm 12 contacts the back plate 10a. 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 ΔV _L is the volume change amount of the right half of the pressure measuring chamber 6, 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 understood from FIG. 5, a larger differential pressure ΔP ₁ is obtained for the stronger silicon diaphragm.
Alternatively, a small pressure difference ΔP ₂ can be applied to the weaker one, and a pressure difference in a wide range of ΔP _{1 to} ΔP ₂ with improved input / output characteristics can be detected. Further, since a pressure of ΔP ₁ or ΔP ₂ or more is not applied to the silicon diaphragm, it is possible to measure the differential pressure regardless of the pressure of the measurement fluid.

[0017]

However, in such a device, since the hardness of the center diaphragm changes within the measurement pressure range, the drop amount of the input pressure due to the movement of the seal diaphragm changes, and the input / output is changed. The characteristics deteriorate. 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 momentary excessive pressures from the high pressure side and the low pressure side and having a wide measurement range and improved input / output characteristics.

[0018]

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. A movement preventing means provided so that the diaphragm is not displaced toward the housing side by a certain amount or more, a silicon diaphragm having a pressure-electricity conversion element provided in the housing, and a high pressure side chamber and a low pressure side chamber in the housing together with the silicon diaphragm. A center diaphragm provided so as to divide the low pressure side chamber into a first chamber and a second chamber which divides the low pressure side chamber into a first chamber and a second chamber. In the measurement range of (1), the center diaphragm and the leaf spring are in contact with each other, which constitutes a differential pressure measuring device.

[0019]

In the above structure, the center diaphragm and the leaf spring are in contact with each other and operate with respect to the measured pressure difference in the normal measurement range. When an overpressure is applied from the high pressure side, the center diaphragm and the leaf spring come into contact with each other up to a predetermined pressure above the measurement range during normal operation, the diaphragm diaphragm is seated on the housing at a predetermined pressure, and a pressure higher than that is applied. Prevents it from being applied to the silicon diaphragm.

When an overpressure is applied from the low pressure side,
The center diaphragm and leaf spring come into contact with each other up to a specified pressure above the normal measurement range, and only the center diaphragm moves at a specified pressure, and the diaphragm diaphragm sits on the housing at a specified pressure above the specified pressure. Prevents pressure from being applied to the silicon diaphragm. Hereinafter, detailed description will be given based on examples.

[0021]

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. 4 represent the same functions. Only parts different from FIG. 4 will be described below. 21 is
A 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 and a low pressure side chamber.

Reference numeral 22 is a leaf spring provided in the low pressure side chamber so as to divide the low pressure side chamber into a first chamber 23 and a second chamber 24. Reference numeral 25 is a communication hole that is provided in the leaf spring 22 and connects the first chamber 23 and the second chamber 24. The leaf spring 22 may have a waveform similar to that of the center diaphragm 21 or a flat plate. Further, the diameter may be the same as that of the center diaphragm 21.

In the above-mentioned structure, the center diaphragm 21 with respect to the measured differential pressure in the normal measurement range.
And the leaf spring 22 come into contact with each other to operate. When an excessive pressure is applied from the high pressure side, the center diaphragm 21 and the leaf spring 22 are operated in contact with each other up to a predetermined pressure above the measurement range in the normal state, and the diaphragm diaphragm 12 is seated on the housing 1 at the predetermined pressure. , Prevents a higher pressure from being applied to the silicon diaphragm 8.

When an overpressure is applied from the low pressure side,
The center diaphragm 21 and the leaf spring 22 come into contact with each other up to a predetermined pressure above the normal measurement range, and only the center diaphragm 21 moves at a predetermined pressure, and the diaphragm diaphragm 13 is seated on the housing 1 at a constant pressure above the predetermined pressure. However, it prevents the pressure higher than that from being applied to the silicon diaphragm 8.

FIG. 2 shows the relationship between the pressure P and the volume change amount ΔV in this embodiment. In response to an input from the high pressure side, the center diaphragm 21 and the leaf spring 22 move while being in contact with each other, and the diaphragm diaphragm 12 is moved to the housing 1 at the point f.
To prevent any further pressure from being applied to the silicon diaphragm 8.

In response to an input from the low pressure side, the center diaphragm 21 and the leaf spring 22 move in contact with each other, only the center diaphragm 21 moves from the point e, and the diaphragm diaphragm 12 moves to the housing 1 at the point g. It is seated and prevents any further pressure from being applied to the silicon diaphragm 8. Within the measurement range (ΔP _{1 to} ΔP ₂ ), since the center diaphragm 21 and the leaf spring 22 move while being in contact with each other,
The rigidity of the center diaphragm 21 and the leaf spring 22 is uniform, that is, the pressure drop due to the movement of the diaphragms 12 and 13 is also uniform.

As a result, (1) Since the center diaphragm 21 and the leaf spring 22 move while being in contact with each other within the measuring range, the hardness can be made uniform and the input / output characteristics can be improved. Can be done. (2) Within the measurement range, the center diaphragm 21 and the leaf spring 22 are configured to move while being in contact with each other even with respect to the L-side input.
02 because the amount of movement of 02 becomes small,
Since the filling amount of the can be reduced, the stress generated in the center diaphragm 21 can be reduced and the durability can be improved.

Further, temperature error due to expansion and contraction of the enclosed liquid 102 can be reduced. FIG. 3 is an explanatory diagram of a main part configuration of another embodiment of the present invention. In this embodiment, the housing 1 is provided with a communication hole 26 that connects the first chamber 23 and the second chamber 24.

[0029]

As described above, according to the present invention, the housing filled with the enclosed 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. Movement preventing means provided so as not to be displaced, and a silicon diaphragm having a pressure-electric conversion element provided in the housing,
A center diaphragm provided in the housing together with the silicon diaphragm to divide into a high pressure side chamber and a low pressure side chamber, and a low pressure side chamber provided in the low pressure side chamber to divide the low pressure side chamber into a first chamber and a second chamber. And a leaf spring provided in the flat spring, and the center diaphragm and the leaf spring are in contact with each other in a normal measurement range.

As a result, (1) Since the center diaphragm and the leaf spring are configured to move while being in contact with each other within the measurement range, the hardness can be made uniform and the input / output characteristics can be improved. .. (2) In the measurement range, the center diaphragm and the leaf spring are configured to move while being in contact with each other even with respect to the L-side input, so that the hardness becomes harder than the conventional example,
Since the movement amount of the filled liquid 102 is reduced, the filled amount of the filled liquid 102 can be reduced accordingly, so that the stress generated in the center diaphragm 21 can be reduced and the durability can be improved.

Further, temperature error due to expansion and contraction of the enclosed liquid 102 can be reduced. Therefore, according to the present invention, it is possible to realize a differential pressure measuring device capable of protecting the sensor main body portion against momentary excessive pressures from the high pressure side and the low pressure side and having a wide measurement range and improved input / output characteristics. Can be done.

[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 explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 4 is an explanatory diagram of a configuration of a conventional example that is generally used in the past.

5 is an operation explanatory diagram of FIG. 4;

[Explanation of symbols]

 1 ... Housing 2 ... High-pressure side flange 3 ... Low-pressure side flange 4, 5 ... Inlet port 6 ... Pressure measuring chamber 6A, 6B ... Back plate 8 ... Silicon diaphragm 9 ... Support body 10, 11 ... Pressure introducing chamber 10A, 11A ... Back plate 12,13 ... Separation diaphragm 14,15,16,17 ... Communication port 21 ... Center diaphragm 22 ... Plate spring 23 ... First chamber 24 ... Second chamber 25,26 ... Communication holes. 80 ... Strain gauge

Claims (1)

[Claims] 1. A housing filled with an enclosed liquid, a pair of diaphragms provided on both sides of the housing, and a movement preventing member provided so that the diaphragms are not displaced toward the housing for a certain amount or more. Means, a silicon diaphragm having a pressure-electric conversion element provided in the housing, a center diaphragm provided in the housing together with the silicon diaphragm to divide into a high-pressure side chamber and a low-pressure side chamber, and the low-pressure side The low-pressure side chamber is provided inside the chamber, and the low-pressure side chamber
A differential pressure measuring device comprising: a chamber and a leaf spring provided so as to be divided into two parts, and the center diaphragm and the leaf spring are in contact with each other in a normal measurement range.