JPS6042351Y2 - pressure gauge - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a pressure gauge.

More specifically, a diaphragm that is displaced in response to the pressure of the fluid to be measured is used as a moving capacitance electrode, and a fixed capacitance electrode is placed opposite to this diaphragm. This relates to a pressure gauge that detects changes.

FIG. 1 shows a conventional example of a pressure gauge that has been commonly used.

In the figure, 1 is a disk-shaped measuring diaphragm that is attached with a large tension applied in the radial direction, and 2 is a cylindrical body that clamps the periphery of the measuring diaphragm 1, and a recess 21 is provided on the circumferential surface. It is being

22 and 23 are spherical recesses provided on both sides of the measuring diaphragm 1 of the body 2.

Reference numerals 24 and 25 are connection holes that connect the recess and the outside.

31 and 32 are fixed capacitance electrodes provided on the surfaces of the recesses 22 and 23 facing the measurement diaphragm 1.

Reference numeral 4 denotes an insulator that insulates the fixed electrodes 31 and 32 from the body 2, and in this case, a glass material is used.

Reference numeral 5 denotes a cylindrical housing, into which the body 2 is inserted and fixed.

51 is a recess provided in the housing 5 opposite to the recess 21.

Thus, the recess 21 and the recess 51 constitute a chamber 52.

Seal diaphragms 6 and 7 cover the outer surfaces of the body 2 and the housing 5 and form chambers 61 and 71, respectively.

Reference numerals 62 and 72 denote presser rings that fix the peripheral edge of the seal diaphragm 6.7 to the housing 5, respectively.

63 and 73 are the recesses 22 and 23 and the communication hole 24.
25 and chambers 61 and 71, such as silicone oil.

Reference numerals 8 and 9 denote covers that respectively cover the seal diaphragm 6.7 and the presser ring 62.72 to form a measurement chamber 81.91.

Numerals 10 and 11 are bolts and nuts for tightening the covers 8 and 9.

In such a device, when the fluid to be measured is introduced into the measurement chamber 81.91, respective pressures are applied to both sides of the measurement diaphragm 1 via the seal diaphragm 6.7 and the filled liquid 63.73, and the measurement The diaphragm 1 is displaced depending on the differential pressure.

This displacement is measured by using the measurement diaphragm 1 as a moving capacitance electrode,
By detecting the difference in capacitance with the fixed capacitance electrodes 31 and 32, it can be detected as an electrical signal.

■The output of a pressure gauge with such a spherical electrode.

0. is generally expressed by the following formula.

a2 I ott"↑・Ding ΔP (1) ■ o □; Output ΔP; Input pressure due to differential pressure; Constant T; Tension of diaphragm 1 (large tension is applied in advance, so the change due to differential pressure input ΔP is It is negligibly small and considered constant.

) a; radius d of diaphragm 1 ; spherical depth from the position of diaphragm 1 in the undisplaced state; However, when used under high static pressure, due to high static pressure,
The area of the body 2 and the housing 5 that receives pressure from the recesses 22 and 23 is the area of the seal diaphragm 6.
Since the area that receives pressure from the diaphragm 7 side is large, a compressive load is applied to the joint part of the body 2 between the measurement diaphragm 1 and the body 2, and although the joint part is small, it is elastically deformed in the direction perpendicular to the diaphragm 1, and The diaphragm 1 also deforms in the radial direction.

Figure 4 shows the deformation.

The deformation caused by the above-mentioned compressive load is symmetrical with respect to the diaphragm 1, so FIG. 4 shows only the deformation of the body 2 on one side.

To simplify the explanation, the welded portion between the diaphragm 1 and the body 2 is omitted.

The solid line shows the deformed state when high static pressure is not applied, and the dashed line shows the deformed state when high static pressure is applied.

Due to the compressive load, the outer peripheral end of the body 2 is extended by δ.

In addition, in the direction perpendicular to the diaphragm 1, it contracts by Ad,
Accordingly, the wall surface of the recess 22 and the circumferential edge of the measuring diaphragm 1 come into contact, and the effective radius a of the measuring diaphragm 1 also increases by Δa.
Decrease.

Due to the radial extension δ of the body 2, the tension T of the diaphragm 1 changes by AT.

This change in tension T cannot be ignored.

That is, in a diaphragm to which a large tension is applied in advance, changes in the tension T of the diaphragm 1 due to the differential pressure ΔP can be ignored, but changes in the tension T due to elastic deformation due to high static pressure cannot be ignored.

Therefore, under high static pressure, the output ■.

ut-s is expressed as equation (2).

K (Foundation) 4-variant ΔP (2) IoUL-8-T+ΔTd-Ad Now, the static pressure is 100 kg/al! When this occurs, the compressive load applied to the body 2 is approximately 500 to 1000 kg, and the deformation of the body 2 due to this is both δ and Δd.
It is approximately 0.5 μm or less.

Even if the depth change Δd″==0.5 μm, it becomes large as Δd=30 μm because the radius of the spherical surface is large.

Therefore, if we ignore δ with respect to Δa, if the spherical surface is formed with a radius of curvature R as shown in Figure 2, then (
3) The formula holds true.

(Equation (3) will be explained later.

) Including two-haired day C- d-Ad-d-2R (31 (2), (From equation 31, I out-s under high static pressure becomes equation (4).

K a2 ■o,, -”=T+ AT” dΔP(4), that is, (1
), it is affected by the tension change ΔT.

○ Explanation of equation (3) When static pressure is O R2= (R-d) 2 +a2 0=-2Rd+d2+a2 Because d<a 2 Ding=water Under high static pressure R2= (R-(d-Ad))"+(a-Δa) 0=-2R(d-Ad)+ (a-Δa)2 (d-Ad)<(a-Δa) (a-Δa)2 d-Δd=water (d-Ad) Because it is , quantity value the=C=8 "d-Δdd The present invention solves this problem.

An object of the present invention is to provide a pressure gauge with good characteristics and less error due to the influence of high static pressure.

In the present invention, the radius a of the diaphragm 1 does not change much under high static pressure, and the changes in the tension T and the spherical depth d of the diaphragm 1 cancel each other out.

That is, the aim is to achieve T-d=(T+ΔT)(d-Δd).

FIG. 3 is an explanatory diagram of the main part of an embodiment of the present invention.

In the figure, the same symbols as in FIG. 1 indicate the same functions.

Hereinafter, only the differences from FIG. 1 will be explained. 221.23
Reference numeral 1 denotes a step-like stepped portion having a surface perpendicular to the diaphragm 1, which is provided in a ring shape on the periphery of the recesses 22 and 23 at the junction with the measurement diaphragm 1.

FIG. 5 shows how the device of the present invention is modified.

Similar to the conventional example described above, only the deformation of the body 2 on one side is shown.

The solid line shows the deformed state when no high static pressure is applied, and the dashed line shows the deformed state when high static pressure is applied.

Due to the compressive load, it contracts by δ in the radial direction and Δd in the orthogonal direction.

According to calculations, when the depth m of the stepped portions 221 and 231 in the direction perpendicular to the diaphragm 1 is approximately m<50 μm, δ becomes a value of 0.5 μm or less, as in the conventional example.

The tension T changes by ΔT depending on δ, but as shown in Fig. 5,
The radius a of the measuring diaphragm 1 (usually a = 15
~20Trr! Changes in n) can be ignored.

The tension T and the change in the spherical depth d are designed to cancel each other out.

As a result, as in the conventional example, the change in the tension T of the diaphragm 1 due to the static pressure Ps is the output ■.

0. It is possible to obtain a product with few errors and to greatly improve the characteristics without directly affecting the performance.

In the above-mentioned embodiment, the stepped portions 221 and 231 are described as having a step-like shape, but the present invention is not limited to this. Bye.

Moreover, even if the radius a changes very slightly,
The degree of contribution to improving the characteristics of the device is large, and the practical effects are large.

As explained above, according to the present invention, it is possible to realize a pressure gauge with good characteristics and fewer errors due to the influence of static pressure.

[Brief explanation of drawings]

Fig. 1 is a conventional example of a pressure gauge that has been commonly used in the past, Fig. 2 is an explanatory diagram of the original version of Fig. 1, Fig. 3 is a diagram showing the main part of an embodiment of the present invention, and Fig. 4 is a diagram showing the main parts of an embodiment of the present invention. 1 is an explanatory diagram of the operation of FIG. 1, and FIG. 5 is an explanatory diagram of the operation of FIG. 3. 1...Diaphragm, 2...Body,
22, 23... recess, 221, 231...
...Stepped portion, 24, 25...Communication hole, 31.32
... Fixed capacitance electrode, 4 ... Insulator, 5
...Housing, 52...Room, 6.7
... Seal diaphragm, 61, 71...
... Chamber, 63, 73... Filled liquid, 8, 9...
...Cover 81.91...Measurement chamber, 10...
...Bolt, 11...Natsuto.

Claims (1)

[Scope of utility model registration request] A pressure receiving area comprising a plate-shaped measurement diaphragm to which a required tension is applied in the radial direction and a body having a spherical recess constituting the diaphragm chamber, and receiving measurement pressure on the outer surface of the body. In a pressure gauge in which the spherical recess has a small pressure-receiving area for receiving measurement pressure, a ring-shaped step having a surface perpendicular to the diaphragm is provided at the joint of the measurement diaphragm of the recess. Features a pressure gauge.