JPS5866832A - Differential pressure measuring device - Google Patents

Abstract

PURPOSE:To decrease errors in static pressure span, temp. span and tightening span by constituting a capsule unit which supports a bellows with insulators in the form of isolating the same from a housing unit. CONSTITUTION:When a high measuring pressure PH is introduced through an introducing groove 611 into a measuring chamber and a low measuring pressure PL through an introducing groove 711, the pressures thereof are transmitted through sealing diaphragms 23, 24 to sealed liquids 4, 5. The pressure difference thereof is converted to force by the rear of a bellows 11, and the movable electrode 12 at the preceding end of the bellows moves rightward and increases the electric capacity between the electrodes 12 and 16, by which a differential pressure is detected. Since a capsule unit 1 is constituted afloat from the chamber 220 provided in a housing unit 2, that is, in a mutually isolated state, the errors in span owing to static pressure, temp. and tightening are decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a differential pressure measuring device. Specifically, the present invention relates to a differential pressure measuring device using a capacitance detection method that applies measuring pressure to the inside and outside of a Perot and detects displacement of the free end of the Perot as a change in capacitance.

In recent years, as a capacitance detection type differential pressure measuring device, a device using a stretch diaphragm as a pressure-displacement conversion element has been widely used.

In such devices, a constant tensile force must always be applied to the diaphragm ◎For this reason,
Fixing the diaphragm (fixing the capsule body and capsule) ・Using must be made of an expensive material that matches the coefficient of linear expansion of the diaphragm so that the tensile force of the diaphragm is not adversely affected by changes in ambient temperature, etc. It becomes expensive.

Next, differential pressure transmitters are often used with large static pressures. In such cases, the large static pressure causes the housing to bulge in the radial direction of the diaphragm, pulling the diaphragm. This causes the diaphragm to become stiffer, which causes static pressure span shift.In order to withstand large static pressure, the housing etc. are tightly tightened with melting etc., but this tightening force also increases. It affects the diaphragm and adversely affects the characteristics as a span shift.

Next, when a large static pressure or overpressure is applied, the housing will be displaced and the static pressure zero shift will result in an overpressure zero shift, or the static pressure or overpressure zero shift based on the IIO modification O residual of Company 7. There is a possibility that this may occur.

The present invention has solved these problems.The purpose of the present invention is to reduce static pressure span error, temperature span error, and tightening span error, and eliminate the risk of static pressure or overpressure zero shift. There is K, which provides differential pressure measuring devices.

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention. In FIG. Spacer 13. It consists of an insulator 14.15 and a fixed electrode 16.17. A plate-shaped movable electrode 12 is fixed to the free end 111 of the bellows 11 so as to be perpendicular to the axis of the bellows 110. As shown in FIG. 2, a large number of semicircular grooves 122 in the same Ib shape are provided near the fixing S of the movable electrode 12 to the free end 111 of the over-range flexible portion 1.
21 are configured. The insulators 14 and 15 have a disk shape and are arranged facing each other on both sides of the movable electrode 120.
A ring-shaped spacer 13 is sandwiched around the periphery. The fixed electrode 16.17 has a ring shape and is placed on the surface of an insulator 14, 15, facing the movable electrode 12, and in this case is formed by vacuum deposition. 1
Reference numeral 8 denotes a substantially disk-shaped support body which is welded and fixed to the fixed end 112 of the bellows and supports and holds the insulator 14. 2 is no.
Uji puffer fish 3. 2. In G, the cylindrical housing body 21.
22, a seal diaphragm 23, 24, and a ring-shaped seal presser 25, 26. Housing body 21.22
A chamber 220K formed by the bottom O recesses 211 and 221
s The capsule 1 is built in, and the outer periphery of the capsule 1 is KWj-contacted 27 so as to be integral with each other. The outer surface portion 212 of the housing body 21.22.
222 is formed with a concentric wavy surface. Capsule Enit 1 touches concave part 211.221 K! The tip of the a-110II fixed end 112 is fixed to the outer flat part 212 of the housing main body 21 without any problem. Thus, a chamber 31 is formed by the outside of the bellows 11, the housing body 21.22, the insulator 14.15, the spacer 13, and the seal diameter 23.2.
24 is the housing body 21.220 outer plane 212.22
2, respectively, and form chambers 231, 241 with the housing body 21, 22, respectively, and the peripheral edges thereof are fixed to the housing body 21, 22 by sealing holders 25, 26. 32F1 is a communication hole that communicates the inside of Be4-11 and the wealth 231. 33 is a communication hole that communicates the chamber 31 and the chamber 241. 4 is the inside of the belly 11, the communication hole 32 and the hole 23.
1 is a sealing liquid filled with silicone oil, and 5 is a sealing liquid such as Krikun oil that connects the chamber 31, the communication hole 33, and the groove 241. 6.7 are seal diaphragms 23.24 respectively
This is a cover that covers the seal presser foot 25, 26 and forms a measurement chamber 61, 71. 611.711 is measurement room 61.7
This is an introduction hole for introducing 1K measurement pressure.

Reference numerals 161 and 171 are leads drawn out from the fixed electrode 16.17, which are hermetically sealed at the outlet from the housing 2. Introduction hole 6
When a measurement pressure PH higher than 11 is introduced into the measurement IM 71 and a measurement pressure PL lower than the introduction hole 711 is introduced into the measurement IM 71, the pressure is applied to the filled liquid 4 through the seal diaphragm 23, 24.
, 5 is converted into force on the front and back surfaces of the bellows 11, and if the effective force of the bellows 11 is Ae, then (p
H-PL) generates AeO force. If the spring constant of bellows 11 is k, then the displacement of the tip of bellows 11 is δ-(PH-
PL) Ae/k. Since the movable electrode 12 is attached to the tip of the bellows 11, when pH>PL, the movable electrode 12 moves to the right in the figure, the capacitance between the electrodes 12 and 16 decreases, and the capacitance between the electrodes 12 and 17 decreases. The capacitance between increases. The relationship between bellows 11 and differential pressure (pH-pL) is
As long as the displacement is small, it is a humming air, and a highly accurate pressure→displacement characteristic can be obtained.

Therefore, if a large static pressure is added as the measurement pressure, 1
When a conventional stretch diaphragm is used as a measurement diaphragm, the housing supporting one stretch diaphragm tilts in the radial direction, and as a result, it pulls on the measurement diaphragm, making the measurement diaphragm itself rigid, resulting in a span error. The drawback of the stretch diaphragm method, which occurs, does not occur.

That is, since the bellows 11 was used as a pressure receiving element, even if the bellows end expands and contracts in the radial direction, only the portion near the bellows end is affected, and the average effective sides of the bellows hardly change. 0 In principle, bellows are considered to be thin-walled cylinders, but in thin-walled cylinders, the length in the axial direction where the deformation of the end of the cylinder casts a shadow on the inside of the cylinder is short, and the dimensions of the main part of the bellows have stable properties. Yes, do. Furthermore, the bellows end portion that is fixed to the pace usually has a slightly elongated cylindrical portion, which also prevents the strain of the pace from being transmitted to the bellows.

In short, even if the nozzle is distorted in the radial direction due to large static pressure, the distortion is absorbed by the cylindrical part of the bellows end.Furthermore, the installation uses a bellows that is inherently resistant to distortion in the part. Because of this, it is possible to obtain a device in which span errors due to static pressure are less likely to occur.

For the same reason, tightening using a bolt cape is resistant to span shift.

Furthermore, in the case of a stretch diaphragm type, if there is a material difference between the housing and the diaphragm, the tension of the diaphragm changes due to temperature changes, resulting in a large span change. Therefore, for example, if a constant elastic material is used as the diaphragm, the housing must also be made of the same material, which is expensive.

In the present invention, even if the housing and the bellows are made of different materials, the deformation of the housing will not be transmitted to the main body of the bellows, as described above, so the material can be selected freely and inexpensive materials can be used. Therefore, there is no temperature span error factor due to differences in linear expansion coefficients.

So, for example, if the bellows is made of a constant modulus material,
There is no material-related temperature span error, and the entire device has extremely small temperature span error, and can be made inexpensive.

Next, as a device, ogAva is required for the case where overpressure is applied as the measurement pressure.

In the present application, (when overpressure is applied, the seal diaphragms 23 and 24 contact the housing body 21 and 22K, respectively, so that the seal diaphragms 23 and 23 are protected from the overpressure.
．． Protect 24. However, in the bellows 11 of the measurement pressure receiving element, the sheath dial 2 area is larger than the area of the bellows, so the displacement of the bellows becomes very large in response to overpressure.

On the other hand, the fixed electrodes 16, 17 and the movable electrode 120 gears are small. Therefore, there is a high possibility that the movable electrode will be destroyed. For this reason, in the past, bellows could not be selected as the measurement pressure receiving element. In the present application, since the over-range flexible portion 121 is provided on the movable electrode 12, the over-range flexible portion 121 flexibly deforms and absorbs the displacement of the bellows 11, so that there is no risk of the movable electrode being destroyed. It will be done.

Next, if we consider the case where an overpressure pH of several 100 kg/cm is applied from the left side of the diagram in FIG. It becomes a thick disk that is supported from one side, and is deformed so that the center part protrudes as shown in FIG. When the overpressure reaches several hundred kg/cm2, this deformation results in a large displacement that cannot be said to be small compared to the measured displacement of Petl-12. Further, this shape of the housing 21 is also transmitted to the insulator 14, and the insulator 14 deforms into a donut-shaped disk whose periphery is supported by the force applied to the inner periphery. At that time, a shift occurs between the insulator 14 and the housing outer surface 212 or between the contact surface between the insulator 14 and the spacer 13, and the zero point does not return to its original state even after the excessive pressure is released, resulting in a shift. ◇ Contrary to this, in this application, the capsule 22 unit 1 is floating from the housing: L unit 2 middle O concave 211.221, and only at the tip of the bellow 11011 fixed end 112. Since it is welded to the housing 21 and the insulator 14 is integrally fixed to the fixed end 112 of the bellows 11 via the support 18, the central part of the outer surface part 212 is displaced and the %-V loss ) will not occur.

From the right side of the diagram in FIG. 1, overpressure p1. , there is a gap between the insulator 15 and the housing body 22, so that the displacement of the outer surface 222 does not affect the housing body 22.

Thus, in the present application, the capsule 22, 1 is arranged in a floating manner in a chamber 220 provided inside the housing unit 2, i.e.
Since the horizontal capsules 22 and 1 are constructed in an insulated manner, static pressure span errors, temperature span errors, tightening span errors, etc. can be reduced.

As explained above, 1. According to the present invention, it is possible to realize a differential pressure measuring device with small static pressure span error, temperature span error, and tightening span error, which is in danger of causing zero static pressure or overpressure (tough). I can do it.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the structure of one embodiment of the present invention O, and Fig. 2 is #1
Fig. 1 is an explanatory diagram of the main parts, and Fig. S is an explanatory diagram of the construction of the cost section of the conventional example. 1 fist... Capsule =, ), 11... Bellow, 111
...Free end, 112...Rigid end, 12...Movable electrode, 121...Overrange W II part, 122
... groove, 13... space? -114, 15...Insulator, 16. : L7... Fixed electrode, 18... Support body, 2... Housing unit, 21.22... Housing body, 220... Wealth, 211.221. ...
Concave portion, Sn2.222...oblique plane, 23.24...
Seal diaphragm, 231.241... fable, 31.
...Chamber, 32.33...Communication hole, 4,5...Filled liquid, 6.7...Cover, 61.71...Measurement chamber, 61
1.711--Introduction hole.

Claims (1)

[Claims] the bellows and the free end of the bellows
A plate-shaped movable electrode having an over-range flexible part formed by a groove provided near the fixed part with the il Luperot, and a plate-shaped movable electrode facing the movable electrode and disposed opposite to each other with a ring-shaped spacer interposed therebetween. a capsule unit consisting of a plate-shaped insulator, a fixed electrode provided on a surface of the insulator facing the movable electrode, and a support fixed to the fixed end of the base and supporting the insulator. The capsule unit is disposed inside the capsule unit without coming into contact with birds, and the fixed end of the perot is fixed, and a concentric wave-shaped surface is formed on the outer surface of the capsule unit. a housing 22, comprising a seal diaphragm whose horse face is fixed to the tongami-shaped cover face and is backed up by the tongami-shaped face in the event of overload; and the seal diaphragm 7.
A differential pressure measuring device comprising a cup (-) that covers the seal diaphragm and forms a measurement chamber.