JPH04320939A - Differential pressure transmitter - Google Patents

Abstract

PURPOSE:To simplify the constitution of a differential pressure transmitter and to protect static pressure and excessive pressure by applying high and low pressures to a pair of pressure receiving diaphragms to detect the strain based on the displacement of the pressure receiving diaphragms corresponding to the differential pressure of said pressures and filling the periphery of a support block to which static pressure is applied with a filler. CONSTITUTION:Receiving diaphragms 21, 22 having diaphragm chambers 23,24 provided on the rear sides thereof are fixed to a main body 20 on both sides thereof. Low and high pressures to be measured are applied to the diaphragms 21, 22 to be guided to both sides of a pressure receiving diaphragm 29 through liquid passages 15,16 and the diaphragm 29 is displaced corresponding to the differential pressure of both pressures and converts the differential pressure to an electric signal on the basis of the resistance change due to strain to measure the differential pressure. In this case, since the outer peripheries of support blocks 32,33 to which static pressure is applied are packed with a filler 42 with low volume elasticity to which predetermined compression strain is applied, the deformation of the blocks 32,33 is suppressed low and external compression force receives no effect of a strain change.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a differential pressure transmitter that receives measured pressures of high pressure and low pressure and detects the differential pressure between them. This invention relates to an improved differential pressure transmitter.

0002

2. Description of the Related Art A differential pressure transmitter is configured to apply measuring pressure to pressure receiving diaphragms on the high-pressure side and low-pressure side, respectively, and to extract the movement of sealing liquid due to this pressure as an electrical signal by, for example, distortion of a semiconductor sensor. There is. However, this type of differential pressure transmitter is sometimes subject to excessive pressure or static pressure, which may reach the semiconductor sensor and damage it, making further measurements impossible. .

[0003] Therefore, various structures have been proposed to protect the sensor from this excessive pressure and static pressure. Figure 3
is a sectional view of a conventional differential pressure transmitter having this type of overpressure/static pressure protection structure. The explanation will be given below based on the same figure. A pressure receiving diaphragm 2 on the high pressure side and a pressure receiving diaphragm 3 on the low pressure side, which are formed in the shape of a corrugated disc, are attached to both sides of the half-split body 1.
, 3 have covers 4 on both sides bolted to the body 1.
A high pressure and a low pressure are applied by the fluid flowing in from the holes 5 and 6 between the body 1 and the body 1, respectively.

On the other hand, the sensor capsule 7 above the body 1
A semiconductor sensor 8 connected to a terminal (not shown) is bonded and held to a substrate 9 in a sensor chamber inside the sensor chamber. It is connected to the high pressure side and the low pressure side of the body 1 via passages 10 and 11. The reason why the sensor 8 has a high pressure side 8a and a low pressure side 8b is because the sensor 8 is bonded to the substrate 9, so it is weak against pressure from the upper side to the lower side, and is weak against pressure from the opposite direction. This is because it is relatively strong against pressure, and its pressure resistance strength is directional.

Reference numeral 12 denotes a center diaphragm formed in the shape of a corrugated disk, and the center diaphragm 12 has an inner chamber provided at the central joint of the body 1, which is divided into a high-pressure side inner chamber 13 and a low-pressure side inner chamber 14. It is fixed to the body 1 so as to be spaced apart from each other. The liquid passages 10 and 11 are connected to the main body interior 1.
3 and 14, respectively. Further, the gaps formed between the pressure receiving diaphragms 2 and 3 and the body 1 are communicated with the main body interior chambers 13 and 14 through liquid passages 15 and 16, respectively.

[0006] Liquid passages 15 and 16 and internal chambers 13 and 14 are connected from the gaps between the pressure receiving diaphragms 2 and 3 and the body 1.
A sealing liquid such as silicone oil 1 is provided between the high pressure side 8a and the low pressure side 8b of the sensor 8 via the liquid passages 10 and 11.
7 is included.

In the above configuration, the pressure receiving diaphragm 2
, 3 as measurement pressures, the pressure receiving diaphragms 2 and 3 are bent and the sealing liquid 17 moves by the amount of compression caused by this, and the difference in the amount of movement of the sealing liquid 17 due to the pressure difference on both sides is compensated for. The differential pressure is measured by detecting it with the sensor 8 and transmitting it as an electric signal. In this case, the center diaphragm 12 is deformed due to the pressure difference on both sides, but does not come into contact with the wall surfaces of the interior chambers 13 and 14 of the main body. Furthermore, the pressure receiving diaphragms 2 and 3 do not come into contact with the body 1 within the normal differential pressure measurement range.

Here, for example, when excessive pressure acts on the high pressure side, the pressure receiving diaphragm 2 on the high pressure side deforms greatly and comes into full contact with the body 1, so that the pressure on the high pressure side is no longer transmitted to the inside. Since the pressure receiving diaphragm 2 is seated on the body 1, the sensor 8 is protected from excessive pressure. This protective function also applies when excessive pressure is applied to the low pressure side.

[0009]

[Problems to be Solved by the Invention] However, the differential pressure transmitter described above has a structure in which the sealing liquid 17 is also filled outside the sensor 8 to protect the sensor 8 from static pressure. The amount of sealing liquid increases, and as a result, the pressure exerted on the center diaphragm 12 and sensor 8 due to expansion of the sealing liquid 17 and excessive pressure when the temperature rises increases, making it difficult to design the strength of these parts.

On the other hand, in order to obtain an advantage in terms of strength, it is necessary to increase the outer diameter of the center diaphragm 12, which becomes an obstacle to miniaturization and cost reduction. It is also assumed that if the sensor 8 is housed inside the body 1 instead of the center diaphragm 12 and these sensors are directly connected through the liquid passages 15 and 16, the amount of sealing liquid 17 will be reduced and the characteristics will be improved. Then, the movement of the sensor 8 due to the pressure increases, making it difficult to realize this due to stress.

[0011]

[Means for Solving the Problems] In order to solve the above problems, the present invention includes a pair of pressure receiving diaphragms that receive measurement pressure covering diaphragm chambers provided on both sides of a main body, and a pressure receiving diaphragm provided inside the main body. A pair of internal chambers of the main body are connected to a diaphragm chamber and separated into two chambers by a center diaphragm, a capsule has an internal space and is fixed to the first main body, and a capsule is provided in the first main body and is provided in the first main body. A pair of support blocks that hold the outer periphery so as to sandwich a pressure diaphragm to form a pair of sensor pressure chambers, and a volumetric shrinkage ratio sealed with a predetermined compressive strain applied to the periphery of these support blocks. This device includes a large filler, a pair of communication holes that communicate the diaphragm chamber and the sensor pressure chamber, and a sealing liquid sealed inside these communication holes.

0012

[Operation] Normally, a pair of pressure-receiving diaphragms receives high and low measurement pressures, and this measurement pressure is led to the interior of each main body and both sides of the pressure-sensitive diaphragm through each communication hole, and the differential pressure between them is This is converted into an electrical signal by distortion based on the displacement of the pressure-sensitive diaphragm corresponding to the pressure, and the differential pressure is thereby measured.

Furthermore, the static pressure based on the measured pressure is applied to the inside of the pair of support blocks, and the capsule is sealed with a predetermined compressive strain applied between the outer periphery of the support blocks and the capsule. Since a filler having a high volumetric shrinkage rate is enclosed, deformation of the support block can be suppressed to a small level.

Furthermore, when excessive pressure is applied, the pressure-receiving diaphragm contacts the back-up plate on the back side, but since there is no sealed liquid circulating around the outside of the sensor section, there is very little sealed liquid as a whole, and the center diaphragm The volume required by the pressure-sensitive diaphragm to absorb the remainder of the excess pressure absorbed by the pressure-sensitive diaphragm is also smaller than that of a conventional differential pressure transmitter having a center diaphragm, and as a result, the characteristics are improved compared to the conventional one.

[0015]

[Embodiments] Hereinafter, embodiments of the present invention will be explained with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention.

Reference numeral 20 denotes a main body having a cylindrical outer shape, and pressure receiving diaphragms 21 and 22 are fixed on both sides of the main body 20 with diaphragm chambers 23 and 24 on the back side thereof. The pressure receiving diaphragm 21 side is a low pressure side, and the pressure receiving diaphragm 22 side is a high pressure side.

In the center of the main body 20, a high-pressure side main body interior 13 and a low-pressure side main body interior 14 are provided separated by a center diaphragm 12, and these are connected to liquid passages 15, 16.
It is communicated with. A cylindrical capsule 25 is fixed to the upper side surface of the main body 20. The interior of the capsule 25 is a cylindrical cavity 27 whose one end is closed with a lid 28. Inside this cavity 27, a pressure-sensitive diaphragm 29 is maintained at a predetermined interval to form sensor pressure chambers 30, 31, and a pair of support blocks 32, 3 are arranged.
3, it is fixed from the periphery and housed as a sensor section 34.

The pressure sensitive diaphragm 29 needs to be bent to some extent due to the differential pressure, and the sensing method for this differential pressure may be a strain gauge method using the pressure sensitive diaphragm 29 as a silicon semiconductor, or a capacitance method. I don't care about that.

These sensor pressure chambers 30 and 31 are formed in the main body 20 and are connected to diaphragm chambers 23 and 2, respectively.
Tubes 35, 36 communicating with 4 and liquid passages 15, 16
It communicates with the diaphragm chambers 23 and 24 via. A sealing liquid 41 such as silicone oil is sealed inside these.

[0020] Furthermore, a filler 42 is sealed in the empty chamber 27 outside the sensor section 34 with a predetermined strain applied thereto. This filler 42 is selected from a compressible resin having a large deposition shrinkage rate, that is, a small bulk modulus.

Next, the operation of the embodiment configured as described above will be explained using the characteristic diagram shown in FIG. Under normal conditions, the pair of pressure receiving diaphragms 21 and 22 receive low and high pressure measurement pressures, and this measurement pressure is applied to the liquid passages 16 and 1.
5 and the pressure sensitive diaphragm 2 via the tubes 35 and 36.
Guided by both sides of 9.

The pressure-sensitive diaphragm 29 is displaced in response to the differential pressure between these low and high pressures, and for example, resistance changes due to strain based on this displacement, or this pressure-sensitive diaphragm 29
The change in capacitance between electrodes (not shown) provided on the inner surfaces of the support blocks 32 and 33 due to the displacement of the support blocks 32 and 33 is converted into an electrical signal, and the differential pressure is thereby measured.

Static pressure due to the measurement pressure is applied inside the pair of support blocks 32, 33, and acts to separate the support blocks 32, 33 into two. Since a filler 42 having a high volume shrinkage rate is sealed under a predetermined compressive strain between the outer periphery and the capsule 25, deformation of the support blocks 32 and 33 is suppressed to a small level. No errors occur.

Furthermore, generally support blocks 32, 33
Various errors occur due to thermal distortion caused by temperature changes due to differences in the coefficient of thermal expansion of the filler 42 and the filler 42, which is made of a resin with a small bulk modulus.
Since the compressive force Pc is applied from the outside of the support blocks 32 and 33 with a sufficient displacement, the compressive force Pc is hardly affected by changes in strain due to thermal expansion of the sensor section 34, and does not become a factor of error.

FIG. 2 shows the displacement (strain) of the filler 42 and the compressive force P.
This is a characteristic diagram showing the relationship with c. As shown in the figure,
Since the filler material 42 has a characteristic of having a small bulk elastic modulus, even if there is a large expansion ΔLT due to a temperature change in the sensor section 34, the change ΔPc in the compressive force Pc applied to the filler material 42 due to this expansion is small. The external pressure applied to 34 hardly changes and does not become an error factor.

When excessive pressure is applied to the high pressure side or the low pressure side, the pressure receiving diaphragms 21 and 22 contact the corrugated backup plate on the back side and the sealing liquid 41 moves. Compared to the amount of the conventional sealing liquid 17 shown in FIG. The volume absorbed by the pressure-sensitive diaphragm 29 is also smaller than that of the conventional differential pressure transmitter shown in FIG. 3, and as a result, the characteristics are improved compared to the conventional one.

Although the description has been made based on a pressure-sensitive diaphragm 29 made of a semiconductor such as silicon, a capacitive type in which the pressure-sensitive diaphragm 29 is a metal diaphragm and the support blocks 32 and 33 are made of an insulating material such as glass may be used. When using the sensor section 45 (not shown), when excessive pressure is applied, the pressure sensitive diaphragm 29
Can be applied directly to an insulating support block.

[0028] By doing this, the effect of overpressure becomes a little large, but it becomes easier to downsize the sensor section.
The amount of sealing liquid in the diaphragm chambers 23, 24 can be further reduced, resulting in improved temperature characteristics. In this case as well, the sensor part is hardly affected by static pressure due to the compressive force applied by the filler from outside. .

[0029]

Effects of the Invention As described above in detail using the embodiments, according to the present invention, a pair of main bodies provided inside the main body, communicated with a diaphragm chamber, and separated into two chambers by a center diaphragm. In addition to providing a chamber, the sensor unit is housed inside the empty chamber, and the surrounding area is filled with a filling material with a high volumetric shrinkage rate that is sealed with a predetermined compressive strain applied, so static pressure and excessive The sensor can be protected from pressure, and the amount of sealing liquid is much smaller than before, so the amount of expansion of the sealing liquid, which is the main cause of temperature errors, is reduced.
The rigidity of the pressure-receiving diaphragm that absorbs this does not need to be reduced so much, and therefore, the outer diameter of the pressure-receiving diaphragm can be reduced, making it possible to achieve downsizing and cost reduction.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing the configuration of one embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the characteristics of the filler in the example shown in FIG. 1;

FIG. 3 is a longitudinal cross-sectional view showing the configuration of a conventional differential pressure transmitter.

[Explanation of symbols]

1 Body 2, 3, 21, 22 Pressure receiving diaphragm 4 Cover 7 Sensor capsule 8 Sensor 12 Center diaphragm 13, 14 Inside the main body 17, 41 Sealing liquid 20 Main body 25 Capsule 27 Vacancy 29 Pressure sensitive diaphragm 30, 31 Sensor pressure chamber 32, 33 Support block 34 Sensor part

Claims (1)

[Claims] Claim 1: A pair of pressure receiving diaphragms that receive measurement pressure covering diaphragm chambers provided on both sides of a main body, and a pair of pressure receiving diaphragms provided inside the main body and communicating with the diaphragm chambers and separated into two chambers by a center diaphragm. A pair of sensor pressure chambers are formed by forming a pair of main body chambers, a capsule having an internal chamber and fixed to the main body, and holding the outer periphery so as to sandwich a pressure-sensitive diaphragm provided in the chamber. a pair of support blocks, a filler having a large volumetric shrinkage rate sealed with a predetermined compressive strain applied around these support blocks, and the diaphragm chamber and the sensor pressure chamber, respectively, communicating with each other. A differential pressure transmitter comprising a pair of communication holes and a sealing liquid sealed inside the communication holes.