JP3039141B2 - Differential pressure measuring device - Google Patents

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 having improved corrosion resistance.

[0002]

2. Description of the Related Art FIG. 3 is an explanatory view of the structure of a conventional example generally used in the prior art.
No. 42. In the figure, reference numeral 1 denotes a housing, a columnar neck 1A, and an end outer peripheral edge 1C of the neck 1A.
, A pressure-receiving portion 1B in the form of a block connected by welding. A high-pressure side flange 2 and a low-pressure side flange 3 are fixed to both sides of the housing 1 by welding or the like. The two flanges 2 and 3 have an inlet 5 for a high-pressure fluid at a pressure PH to be measured and a low-pressure fluid at a pressure PL. An inlet 4 is provided.

[0003] 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 measuring chamber 6 and the silicon diaphragm 8 divide the pressure measuring chamber 6 into two parts. Back plates 6A and 6B are formed on the wall of the pressure measurement chamber 6 facing the center diaphragm 7.

[0004] The center diaphragm 7 is welded to the housing 1 in a ring shape at the periphery thereof. The silicon diaphragm 8 is formed entirely of a single crystal silicon substrate. An impurity such as boron is 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 concave diaphragm as a whole. The four strain gauges 80 are such that when the silicon diaphragm 8 deflects due to the differential pressure ΔP, two are pulled and two are subjected to compression, which are connected to a Wheatstone bridge circuit, The resistance change is detected as a change in the differential pressure ΔP.

A lead 81 has one end attached to the strain gauge 80. Reference numeral 82 denotes a hermetic terminal to which the other end of the lead 81 is connected. The support 9 has a hermetic terminal, and a silicon diaphragm 8 is bonded and 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. A pressure introducing chamber 1 is provided between the housing 1 and the high-pressure side flange 2 and the low-pressure side flange 3.
0 and 11 are formed.

[0006] Separating liquid 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 liquid diaphragms 12 and 13 is formed on the walls 10A and 11A 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 measurement chamber 6 communicate with each other through communication holes 14 and 15.

The space between the liquid diaphragms 12 and 13 is filled with liquids 101 and 102 such as silicon oil.
The sealed liquid reaches the upper and lower surfaces of the silicon diaphragm 8 through the communication holes 16 and 17, and the sealed liquid 101, 1
02 is a center diaphragm 7 and a silicon diaphragm 8
However, care is taken to make the amounts substantially equal. Reference numeral 21 denotes sealing means provided in the pressure receiving portion 1B for sealing the sealed liquids 101 and 102 in the housing 1. In this case, it is composed of a sealing hole 211, a sealing ball 212 and a sealing screw 213.

In the above configuration, when a pressure acts from the high pressure side, the pressure acting on the diaphragm 12 becomes:
The liquid is transmitted to the silicon diaphragm 8 by the filling liquid 101. On the other hand, when pressure acts from the low pressure side, the pressure acting on the liquid diaphragm 13 is transmitted to the silicon diaphragm 8 by the filling liquid 102.

As a result, the silicon diaphragm 8 is distorted in accordance with the pressure difference between the high pressure side and the low pressure side, and the amount of this distortion is electrically taken out by the strain gauge 80, and the differential pressure is measured. .

[0010]

However, in such an apparatus, since the center diaphragm 7 generates a large stress, a material having a high proof stress is used. Generally, high strength steel is used. Such materials are
Poor corrosion resistance. On the other hand, since the pressure receiving portion of the differential pressure measuring device is exposed to a corrosive atmosphere, a material having good corrosion resistance is used, and generally, stainless steel such as SUS316 is used. Thus, since the weld 71 is an alloy of stainless steel and steel tensile steel, the corrosion resistance is reduced, and is protected by a silicon coating material or the like, but sufficient corrosion resistance cannot be obtained with this level. The present invention solves this problem.

An object of the present invention is to provide a differential pressure measuring device having improved corrosion resistance.

[0012]

In order to achieve this object, the present invention comprises a center diaphragm made of a material having low corrosion resistance but high strength, and a material having high corrosion resistance sandwiching the center diaphragm. A housing,
In a differential pressure measuring device having a ring-shaped weld provided at a joint between the housing and the center diaphragm, a first weld having a penetration section that is long in the ring surface direction and short in a direction perpendicular to the ring surface is provided. And a second welded portion formed after the formation of the first welded portion and having a penetration cross-sectional shape that is shorter in the direction of the ring surface and longer in the direction perpendicular to the ring surface. This is a device configuration.

[0013]

In the above construction, when pressure acts from the high pressure side, the pressure acting on the liquid diaphragm is transmitted to the silicon diaphragm by the sealed liquid. On the other hand, when pressure acts from the low pressure side, the pressure acting on the liquid diaphragm is transmitted to the silicon diaphragm by the sealing liquid. Therefore, the silicon diaphragm is distorted in accordance with the pressure difference between the high pressure side and the low pressure side, and the amount of this distortion is electrically extracted due to the strain gauge, and the differential pressure is measured.

Thus, the first welded portion having a penetration section longer in the ring surface direction and shorter in the direction perpendicular to the ring surface is formed after the formation of the first welded portion, and the penetration section shape is shorter in the ring surface direction and is perpendicular to the ring surface. Since the welded portion including the second welded portion that is long in the direction is configured, a differential pressure measuring device that can ensure the welding strength of the welded portion and has improved corrosion resistance can be obtained.
Hereinafter, a detailed description will be given based on embodiments.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
FIG. 2 is a detailed explanatory diagram of FIG. In the figure, the configuration of the same symbol as in FIG. 3 represents the same function. Hereinafter, only differences from FIG. 3 will be described. 31 is a first welding portion 32 whose penetration cross section is long in the ring surface direction and short in the direction perpendicular to the ring surface.
And a second cross-sectional shape formed after the formation of the first welded portion 32 is short in the direction of the ring surface and long in the direction perpendicular to the ring surface.
This is a welded portion including a welded portion 33. In this case, welding is performed with an electron beam.

In the above configuration, when pressure acts from the high pressure side, the pressure acting on the diaphragm 12 becomes:
The liquid is transmitted to the silicon diaphragm 8 by the filling liquid 101. On the other hand, when pressure acts from the low pressure side, the pressure acting on the liquid diaphragm 13 is transmitted to the silicon diaphragm 8 by the filling liquid 102. Accordingly, the silicon diaphragm 8 is distorted according to the pressure difference between the high pressure side and the low pressure side, and the amount of this distortion is electrically extracted by the strain gauge 80, and the differential pressure is measured.

Thus, the first welded portion 32 and the first welded portion 32 whose penetration cross section is long in the ring surface direction and short in the direction perpendicular to the ring surface.
The second welded portion 3 formed after the formation of the welded portion 32 and having a penetration cross-sectional shape that is short in the ring surface direction and long in the direction perpendicular to the ring surface
3, the welding pressure of the welded portion 31 can be ensured and the differential pressure measuring device with improved corrosion resistance can be obtained.

That is, in the first welded portion 32, the penetration shape is made thinner and deeper in order to obtain welding strength and reduce thermal deformation. In the second welded portion 33, the penetration shape is made shallow and wide in order to improve the corrosion resistance of the surface of the pressure receiving portion. Here, the first welded portion 32 is made of SUS31 having good corrosion resistance.
The stainless steel No. 6 and the steel tensile steel having poor corrosion resistance are uniformly mixed by about half. For this reason, the concentrations of chromium and nickel, which are elements that improve the corrosion resistance of SUS316 stainless steel, are reduced to about half. As a result, the first weld 3
Part 2 has reduced corrosion resistance.

In the second welding portion 33, the first welding portion 32 and S
Since about half of the US316 stainless steel is mixed, the concentration of chromium and nickel is about 3/4 of that of the SUS316 stainless steel, and the corrosion resistance is improved as compared with the case where only the first welded portion 32 is used. , Sufficient corrosion resistance is obtained. Generally, effective corrosion resistance is obtained at a chromium concentration of 10% or more.

[0020]

As described above, according to the present invention, a center diaphragm made of a material having low corrosion resistance but high proof strength, a housing made of a material having high corrosion resistance sandwiching the center diaphragm, A differential pressure measuring device comprising: a ring-shaped weld provided at a joint with the center diaphragm; a first weld having a penetration cross-sectional shape longer in the ring surface direction and shorter in a direction perpendicular to the ring surface; A differential pressure measurement device comprising a second welded portion formed after the formation of the first welded portion and having a second welded portion whose penetration cross section is shorter in the direction of the ring surface and longer in the direction perpendicular to the ring surface. did.

As a result, the first welded portion whose penetration cross section is long in the ring surface direction and short in the direction perpendicular to the ring surface is formed after the formation of the first welded portion, and the penetration cross section is short in the ring surface direction and is perpendicular to the ring surface. Since the welding portion including the second long welding portion is configured, the welding strength of the welding portion can be secured, and a differential pressure measuring device with improved corrosion resistance can be obtained.

Therefore, according to the present invention, a differential pressure measuring device with improved corrosion resistance can be realized.

[Brief description of the drawings]

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

FIG. 2 is a detailed explanatory view of a main part of FIG. 1;

FIG. 3 is an explanatory diagram of a configuration of a conventional example generally used in the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Housing 1A ... Neck 1B ... Pressure receiving part 1C ... Welding 2 ... High-pressure side flange 3 ... Low-pressure side flange 4 ... Inlet 5 ... Inlet 6 ... Pressure measuring chamber 6A ... Back plate 6B ... Back plate 7 ... Center diaphragm 8 ... Silicon diaphragm 9 ... Support 10 ... Pressure introduction chamber 10A ... Back plate 11 ... Pressure introduction chamber 11A ... Back plate 12 ... Separation diaphragm 13 ... Separation diaphragm 14 ... Communication hole 15 ... Communication hole DESCRIPTION OF SYMBOLS 16 ... Communication hole 17 ... Communication hole 31 ... Welded part 32 ... 1st welded part 33 ... 2nd welded part 80 ... Strain gauge 101 ... Filled liquid 102 ... Filled liquid

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-125937 (JP, A) JP-A-61-2033 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01L 13/06

Claims (1)

(57) [Claims] 1. A center diaphragm made of a material having low corrosion resistance but high strength, a housing made of a material having high corrosion resistance sandwiching the center diaphragm, and a joint between the housing and the center diaphragm. A differential pressure measuring device comprising a ring-shaped welded portion, a first welded portion having a penetration cross section longer in the ring surface direction and shorter in a direction perpendicular to the ring surface, and a penetration formed after the formation of the first welded portion. A differential pressure measuring device, comprising: a welding portion having a second welding portion having a sectional shape shorter in the ring surface direction and longer in a direction perpendicular to the ring surface.