JPS59145940A - Differential pressure and pressure transmitting device - Google Patents

Abstract

PURPOSE:To simplify the structure of a titled device and to make it small- sized by providing a measuring diaphragm having a thick part formed on the surface, and a substrate which is placed opposingly on one side or both sides of this diaphragm and forms a chamber together with this diaphragm, or the like. CONSTITUTION:A differential pressure and pressure transmitting device has a measuring diaphragm 18 having thick parts 18a, 18b and 18c formed at plural parts on the surface of a pressure measuring part, substrates 19, 20 which are placed oppositely on one side or both sides of this diaphragm 18 and form a chamber together with this diaphragm 18, and measured pressure leading-in paths 19a, 20a provided on at least one of these substrates, etc. According to such constitution, a gap between the center thick part 18a and electrodes 23, 24 is varied by a displacement of the measuring diaphragm 18, an electric signal corresponding to a differential pressure is obtained from a variation of an electrostatic capacity during that time, and the structure can be simplified and made small-sized as compared with a conventional one.

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application The present invention relates to the improvement of differential pressure/pressure transmitters, and particularly to the improvement of differential pressure/pressure transmitters having a mechanism for protecting the measuring diaphragm from excessive pressure. Regarding.

b. Conventional Example A conventional device having a mechanism for protecting the measuring diaphragm from excessive pressure is known as shown in Japanese Patent Application Laid-open No. 79582/1982. FIG. 1 shows the differential pressure transmitter in the known example. In this figure, 1.2 is a member forming the main body of the differential pressure transmitter, and pressure receiving diaphragms 5 and 6 are attached to outer end surfaces 3 and 4, respectively. A recess is formed in the center of the abutting surfaces of the members 1 and 2, respectively. 7 is a compensating diaphragm for overpressure protection, which is held by the outer peripheral end surface of the abutting surface and covers the space formed by the recessed portion 2.
Divided into two compensation chambers 8.9.

Reference numerals 10 and 11 denote pressure receiving chambers formed between the pressure receiving diaphragms 5 and 6 and the outer end surfaces 3 and 4 of the member 1.degree. 2, respectively. The pressure receiving chamber 10 and the compensation chamber 8 are connected by a passage 12, and the pressure receiving chamber 11 and the compensation chamber 9 are connected by a passage 13.

14 is a measurement chamber provided in the member 1, with passages 15 and 16.
via channels 12 and 13, respectively. Reference numeral 17 denotes a measurement diaphragm made of, for example, a semiconductor, provided in the measurement chamber 14.

Compensation room 8, 9. Pressure receiving chambers 10, 11. , measurement chamber 14 passage 1
2, 13, 15, and 16 are filled with incompressible sealing liquid, such as silicone oil.

In such a device, for example, when a high pressure side pressure pT is applied to the pressure receiving diaphragm 5, but a low pressure side pressure Pr+ is applied to the pressure receiving diaphragm 72, the pressure applied to each pressure receiving diaphragm is measured via a sealing liquid. Pressure P) applied to diaphragm 17 and compensating diaphragm 7)1. The measuring diaphragm 17 is displaced according to the differential pressure of PL.

For example, in the case of a semiconductor measuring diaphragm in which a silicon diaphragm is used as the measuring diaphragm 17 and a piezoresistive element is formed by diffusion on the surface (C), the displacement of the measuring diaphragm 17 distorts the piezoresistive element, resulting in a resistance value of K. An electrical signal corresponding to the displacement can be obtained from the change.

On the other hand, if excessive pressure is applied to the pressure receiving diaphragm 5 due to an operational error or the like, the pressure receiving diaphragm 5 deforms and comes into close contact with the outer end surface of the member 1. At this time, the sealing liquid displaced by the pressure receiving diaphragm 72 is absorbed by the compensating diaphragm 7 as the volume of the compensating chamber 8 increases. Oka, compensation diaphragm 7
is dimensioned so that even if the pressure receiving diaphragm 5 (6) comes into close contact with the outer end surface 3 (4) due to excessive pressure, it will not come into contact with the surrounding wall.

Once the pressure-receiving diaphragm 5 is in close contact with the outer end surface 3, the pressure-receiving diaphragm 5 will not deform even if more pressure is applied, so the sealing liquid will not move and the measurement diaphragm 1
7 and the compensation dial 7. No further pressure is applied to the ram 7. Therefore, if the pressure is received within the permissible pressure of the measuring diaphragm 17, and the diaphragms 5 and 6 are set in close contact with the outer end surfaces 3 and 4, even if excessive pressure is applied, the measuring diaphragm 17 will not be damaged or destroyed. There isn't.

However, in such a differential pressure transmitter, the contact portion that is not directly involved in pressure measurement, that is, the compensation diaphragm 7
, compensation room 8, 9. It is necessary to provide passages 12 and 13 communicating with these, which complicates the structure and makes it difficult to downsize.

C1 Objective of the Invention The technical problem to be solved by the present invention is to apply measuring pressure to both sides or one side of a measuring diaphragm, and convert the differential pressure or the displacement of the measuring diaphragm according to the pressure into an electrical signal. The present invention aims to reduce the size of a differential pressure/pressure transmitter by eliminating an overpressure prevention mechanism provided separately from the pressure measuring section.

D0 Structure of the Invention The structure of the present invention consists of: (1) a measuring diaphragm having a pressure measuring portion on its surface with a plurality of thick-walled portions formed thereon; a substrate disposed oppositely on one or both sides of the diaphragm and forming a chamber together with the diaphragm; It consists of a measuring pressure introduction path provided on at least one side of the substrate, and a means for converting the displacement of the measuring diaphragm due to differential pressure/pressure into an electrical signal, and when excessive pressure is applied to the measuring diaphragm, The diaphragm has a structure in which the thick inner part of the diaphragm contacts the wall surface of the substrate to prevent the diaphragm from being destroyed.

■1 action The above technical means works as follows.

That is, when measurement pressure is introduced into the measurement chambers provided on both sides or one side of the measurement diaphragm, the thin wall portion between the thick wall portions of the measurement diaphragm is bent, and the contact between the thick wall portion and the wall surface is caused to bend. The gap changes.

The displacement of the measurement diaphragm is detected, for example, as a change in the resistance value of a piezoresistor provided in the thin part, or as a change in the capacitance between the thick interior using a conductive member and electrodes provided on the wall surface. .

When excessive pressure is applied, the thin portion continues to flex until the thick interior contacts the wall surface. When the thick portion touches the wall surface, it will not bend any further. If the width and thickness of the thin section are selected to be sufficient to withstand excessive pressure, the measuring diaphragm will not be destroyed.

F. EXAMPLE The present invention will be described in detail below with reference to the drawings. Fig. 2 is a longitudinal sectional view showing the pressure measuring part in the present invention, Fig. 3 is a cross sectional view of the diaphragm shown in Fig. 2 taken along the A-A plane, and Fig. 4 is shown in Fig. 2. FIG. 2 is a cross-sectional view of a differential pressure transmitter according to the present invention including a pressure measuring section. 'First, in FIGS. 2 and 3, reference numeral 18 denotes a measurement diaphragm, which has a plurality of annular thick-walled parts 1 concentrically surrounding a central disk-shaped thick-walled part 18a.
sb18C! 75! G is being kicked. The measurement diaphragm 18 is made of single crystal silicon or Ni-5PANO.
A conductive elastic material such as Zapphire or an insulating elastic material such as Zaphire is used, and in the latter case, a conductive film is formed for the central thick portion 18aK electrode.

Reference numeral 19.20 denotes an insulating substrate made of Pyrex glass, ceramic, etc., which is provided opposite both sides of the measurement diaphragm 18, and is connected to the thick peripheral portion 18 (l) of the measurement diaphragm 18.
It is fixed by anodic bonding and isostatic pressure. These boards include a high pressure side pressure introduction path 19a and a low pressure side pressure introduction path 20.
a is provided, and measurement chambers 2 are provided on both sides of the measurement diaphragm 18.
1.22 is formed.

23.24 An electrode is provided in the center of the vertical substrate 19.20, facing the thick part 23 of the measuring diaphragm 18, and is made of gold or aluminum. .

25 and 26 are thick portions 181) of the measurement diaphragm 18;
An annular stopper 27 and 28 is provided on the substrate 19 opposite to 180, and an annular stopper 27 and 28 is provided on the substrate 20 opposite to the thick portions 1sb and 1scK.

FIG. 4 shows a differential pressure transmitter according to the present invention, which includes the pressure measuring section described in FIG. 2. In this figure, 29.30
is a member forming the main body of the differential pressure transmitter, and the outer end surfaces 31, 3
Pressure-receiving diaphragms 33 and 34 are attached to 2, respectively. Four central portions KFi of the abutting surfaces of the members 29 and 30 are formed, and the pressure measuring portion described in FIG. 2 is distributed in the cavity 35 formed by these four portions.

36 pieces, pressure receiving diaphragm 33 and outer end surface 3 of part side 29
1, a passage provided between the pressure receiving chamber 37 formed between the pressure receiving diaphragm 34 and the high pressure side pressure introduction path 19a of the front distribution pressure measuring section, 38, between the pressure receiving diaphragm 34 and the outer end surface 32 of the part 30. This is a passage formed between the pressure receiving chamber 39 and the cavity 35.

Similarly, the low-pressure side pressure introduction path 20a of the pressure measuring section is the hollow space 3.
It is open at 5.

Of the 40 leads from the pressure measuring section, one is pulled out from the V measuring diaphragm 18, and the rest are connected to the substrate 19.2.
It is drawn out from electrodes 23 and 24 provided at 0.

Sorry, blank space 35. Pressure receiving chambers 37, 39. The passages 36 and 38 are filled with an incompressible sealing liquid, such as silicone oil.

Next, the operation of this embodiment device will be explained.

When the pressure receiving diaphragm 33 receives the high pressure side pressure pH and the pressure receiving diaphragm 34 receives the low pressure side pressure PL, these pressures are transmitted to the measuring diaphragm 7 ram 18 via the sealing liquid. In the measurement diaphragm 18, the thick parts 18a, 18b, 18
A strain occurs in the thin section between 0 and the peripheral thick section 184, displacing the measuring diaphragm 18. This is from K.
The gap between the central thick portion 18a and ff1Th23.24 changes, and an electrical signal corresponding to the differential pressure is obtained from the change in capacitance during this time.

On the other hand, if excessive pressure is applied due to a misoperation, the measuring diaphragm 18 will be damaged by the thick portions 18al and 18b.

It is necessary to have a size that can flex until 18C touches the substrate 19 or 21C and can withstand the maximum excessive pressure. In a differential pressure transmitter for industrial measurement, the maximum value of excessive pressure is about 300 or more, so it is necessary to have a size and pressure that can withstand such excessive pressure. For example, measuring diaphragm 1
If single-crystal silicon is used for 8, the etching method of semiconductor manufacturing technology can be used, and the thickness of the thin part 1, the thickness of the thick part 1
The widths of 8a, 18b, and 180 can be controlled with extremely high precision.

However, if the thick portion 18a of the measurement diaphragm 18 comes into contact with the electrodes 23, 24 on the substrate 19 or 20, a short circuit may occur between them and the output may become uncertain. In order to avoid such a situation, there is a method of changing the configuration of the output circuit so that when the short circuit accident occurs, the output is swung to the high side, for example.

Another simple method is to form an insulating film on the surface of the measurement diaphragm 18. Specifically, the gap between the thick part 18a of the Fl+ constant diaphragm 18 and the outer shuttle 2B, 24 is about 5 microns, and when the measurement diaphragm I8 is made of single crystal silicon and a silicon oxide film is formed on the surface, this gap is approximately 5 microns. The thickness of the film is approximately 0.4 microns, making it possible to form an ideal insulating film. @Accidents can be prevented.

In addition, when such an insulating film is formed, short circuit accidents caused by conductive dust entering between the thick inside 18a of the measurement diaphragm 18 and the electrodes 23 or 24 can be prevented.

Other embodiments of the present invention will be described below. FIG. 5 is a sectional view of the sensor section when the pressure measuring section is of a resistance type. In this figure, elements K that are the same as those in FIG. 2 are denoted by the same reference numerals, and explanations thereof will be omitted. 41.42 is thick part 1
8a, stoppers 43 and 44 are provided on the substrates 19 and 20, respectively, and 44 are strain resistance elements provided on the v and jaw portions of the measuring diaphragm 18. These strain resistance elements are thermally bonded or pasted, or a measuring diaphragm, 18
If is single A silicon, then Ki [conductor! ! Diffusion formation using manufacturing techniques.

When the thin portion of the measurement diaphragm 18 bends in response to the differential pressure, the resistance values of the strain resistance elements 43 and 44 change, which is detected as an electrical signal. Similarly, the manner of preservation against excessive pressure is exactly the same as in the case shown in FIG.

, FIG. 6 shows the thick part 18a of the measurement diaphragm 18.

1, Rb, and 180 are longitudinal cross-sectional views of a capacitive pressure measuring section formed so that they appear only on one side of a diaphragm. In this figure, the same elements as in FIG. 2 are given the same reference numerals.

In the case of this specific example as well, the manner of maintaining stability against excessive pressure is substantially the same as in the case of FIG. 2 or FIG. 5.

FIG. 7 is a cross-sectional view of a single capacitance type pressure measuring section in which electrodes are provided on only one side of the measuring diaphragm 18 facing each other. In this figure, the same elements as those in FIGS. 2 and 6 are given the same reference numerals. 45 is an fcR-shaped cavity formed by partially cutting out the peripheral thick wall fli+I Rd of the measurement diaphragm 18, and 46 is an F' in this cavity.
A substrate 1 facing the constant diaphragm 18 at a constant distance.
9 is an annular negative electrode provided on the top.

The portion of the measuring diaphragm 18 facing the pole is an extension of the circumference FJl'F and the flesh portion 1B+1, and is not displaced by the differential pressure, and the electrostatic capacity between them does not change. The capacitance of this portion is used as a reference capacitance when measuring the capacitance change between the thick portion 18a and the electrode 23.

FIG. 8 is a cross-sectional view of a diaphragm section showing another example of the measuring diaphragm 18. The intermediate thick portion 18t) of the measurement diaphragm 18 is not limited to the 180mm annular shape,
It may be a dot-shaped thick portion 18e as shown in this figure.

FIG. 9 is a cross-sectional view of a diaphragm portion showing still another specific example of the measurement diaphragm 18.

In the specific example shown in this figure, the overall shape of the measurement diaphragm 18 and the thick portions 18/, 18, and 18h are formed into a rectangular shape. Such a shape can be easily fabricated by anisotropic etching when single crystal silicon is used for the measurement diaphragm 18.

In all of the specific examples of the measuring diaphragm 18 up to now, a thick wall part is formed surrounding a central thick wall part, and the outermost periphery is a thick wall trap. Even if the diaphragm is formed thin, it can be used as the measurement diaphragm 18.

FIG. 10 is a longitudinal sectional view of a capacitive pressure measuring section using such a measuring diaphragm 18. In this figure, the second
Elements that are the same as in the figures are given the same reference numerals.

19' and 20' are insulating substrates with a recess formed in the center, and electrodes 23, 24 and stoppers 25, 25, 27 are provided in the recess.
．． 28 are provided. The measuring diaphragm 18 and the insulating substrates 19', 20' are connected to each other at the peripheral thin portion 181 of the measuring diaphragm 18. =IP+joint, etc.

In the case of anodic bonding, the above peripheral edge is firmly bonded, so
Even if repeated stress is applied to the inner periphery of the joint by displacement of the measuring diaphragm 18, the joint will not come apart.

In the case of this specific example, the appearance of acceleration against excessive pressure is similar to that of the second
tl is substantially the same as in the specific examples shown in FIGS. 5 to 7.

Since the displacement of the measurement diaphragm 18 is different between the central part and the peripheral part, in relation to this, the thick parts 18a and 1
The thickness of the parts on the substrate 19, 20 that are hit by the parts 8b, . ? '
In addition to the misalignment, excessive pressure retention of the measuring diaphragm 18 becomes a problem.

Further, in all of the above-described embodiments of the present invention, measurement pressure is introduced to both sides of the measurement diaphragm 18, and the differential pressure transmitter measures the differential pressure between them, but the present invention is not limited to this. Il
Even in the case of a pressure transmitter in which the substrates are arranged opposite to each other on both sides of the diaphragm 18 and the diaphragm 18, constant pressure is applied to only one side of the diaphragm, and reference pressure or atmospheric pressure is applied to the other side. The present invention can be practiced without any problems.

G0 Effect of the invention According to the invention, the pressure measuring section itself has a measuring diaphragm 1.
8 has a function to protect the membrane from excessive pressure, so the overpressure membrane mechanism that was previously provided separately from the pressure measurement part is no longer necessary, and the transmitter can be made smaller compared to conventional ones. .

Furthermore, since the sealing liquid filled in the chamber for the overpressure protection mechanism no longer has any force, the total amount of sealing liquid can be reduced, and temperature errors due to thermal expansion of the sealing liquid can be kept small.

Furthermore, the fluid whose pressure is to be measured is not corrosive;
If there is no dust or other material that could damage the measurement diaphragm 18, K lj, the measurement diaphragm 18.
In this case, the KIi transmitter can be further downsized since the KIi can be constructed to directly receive the fluid to be measured, and the pressure receiving diaphragms 33, 34, etc. are not required.

tfj:' Explanation of the cylindrical piece on page 1. The first figure is a vertical cross-sectional view showing a conventional differential pressure transmitter. The second figure is a vertical cross-sectional view showing the pressure measuring part in the present invention. The third figure is a second vertical cross-sectional view. FIG. 4 is a cross-sectional view of the measuring diaphragm taken along the A-A plane; FIG. 4 is a vertical cross-sectional view showing the differential pressure transmitter of the present invention equipped with the pressure measuring section shown in FIG. 2; FIG. 7 and 10 are vertical cross-sectional views showing other specific examples of the pressure measuring section in the present invention, and FIGS.
The figure shows another example of the measurement diaphragm according to the present invention.
FIG. 1 is a cross-sectional view of a diaphragm.

18...Measurement diaphragm 1, i8a, 18b.

18C! , 18θ, 18f, 18f...thick part, 19
, 20.19', 20'...substrate 23.24...
Electrode, 43.44°°° Strain resistance element Patent applicant Hokushin Electric Manufacturing Co., Ltd. Representative Masahiro Shimizu No. a1 1 19α 1918 Do0 No. 71'& 12ooL Fig. 8 Fig. 9 Fig. 8 Fig. 110

Claims (1)

[Claims] A measurement diaphragm with thick-walled parts formed in multiple places on the surface, and a measurement diaphragm arranged opposite to each other on one or both sides of this diaphragm,
It consists of a substrate forming a chamber together with this diaphragm, means for introducing measuring pressure to one or both sides of the measuring diaphragm, and means for converting the displacement of the measuring diaphragm due to differential pressure or pressure into an electrical signal, A differential pressure/pressure transmitter comprising a pressure measuring section having a structure in which the thick portion hits the wall surface of the one substrate to prevent destruction of the diaphragm when applied to the measuring diaphragm.