JPH09318480A - Pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent distortion from occurring at the pressure receiving part of a diaphragm at the time of installing the diaphragm into the pressurized reservoir. SOLUTION: This pressure sensor comprises a tubular diaphragm 22 that a distortion detecting part 27 is provided for a pressure receiving part 25 and a pressurized reservoir 21 to which the diaphragm 22 is attached. A flange- shaped overhanging part 30 is formed at the outer circumference of the diaphragm 22. An engagement recessed part 32 in which the overhanging part 30 is engaged with minute clearance 31 is formed at the inner circumference of the pressurized reservoir 21. An O ring 36 is provided between the inner circumference of the engagement recessed part 32 and the outer circumference of the overhanging part 30. Therefore, as the overhanging part 30 is not pressed by the engagement recessed part 32 at the time of installing of the diaphragm 22 into the pressurized reservoir 21, distortion does not occur at the pressure receiving part 25. By this reason, pressure measurement with high accuracy can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor for measuring the pressure of fluid.

[0002]

2. Description of the Related Art Conventionally, as a pressure sensor for measuring the pressure of a fluid, one disclosed in Japanese Utility Model Publication No. 3-63835 or Japanese Utility Model Publication No. 5-19797 is known.

The pressure sensor disclosed in Japanese Utility Model Laid-Open No. 3-63835 will be described with reference to FIG. A diaphragm 2 is mounted in the casing 1. A flange-shaped protruding portion 3 is formed on the outer peripheral portion of the diaphragm 2, and the protruding portion 3
Is fixed by tightening with an annular fixing nut 5 via an annular fixing ring 4. A screw portion 6 for attaching the casing 1 to an object to be measured (not shown) is formed on the outer peripheral portion of the casing 1.

The diaphragm 2 has a pressure receiving portion 7 which receives pressure, and a strain gauge 8 is provided at the center of the pressure receiving portion 7. The strain gauge 8 includes a lead wire 9, a circuit board 10, and a terminal 1.
1 to an external circuit (not shown). An annular groove 12 is formed in a portion of the casing 1 facing the overhanging portion 5, and an O-ring 13 is provided in the annular groove 12.

In this pressure sensor, when the pressure of the fluid acts on the pressure receiving portion 7 through the through hole 14, the strain gauge 8 is deformed in accordance with the pressure, and the amount of deformation of the strain gauge 8 is determined by the circuit board 10.
To convert it to an electric signal and output it to an external circuit to measure the fluid pressure.

The pressure sensor disclosed in Japanese Utility Model Publication No. 5-19797 will be described with reference to FIG. In this pressure sensor, a diaphragm 15 is mounted in a case member 18 together with two O-rings 16 and 17 arranged on the upper surface side and the lower surface side thereof. A strain gauge 20 is provided at the center of the pressure receiving portion 19 of the diaphragm 15.

[0007]

In the case of a pressure sensor using a strain gauge, the strain gauge is 0.1% generated on the surface of the pressure receiving portion.
The following slight strain ε (K · ε = ΔR / R, where K: gauge ratio, ΔR / R: resistance change rate) is converted into an electric signal to measure the pressure. Therefore, if the output error is set within 3%, the strain generated on the surface of the pressure receiving portion due to the clamping, fixing, or mounting of the diaphragm is 0.1 × 0.03 =
It must be 0.003 (%) or less.

According to the pressure sensor shown in FIG. 17, the overhanging portion 3 of the diaphragm 2 is fastened and fixed by the fixing nut 5 via the fixing ring 4. Therefore, due to this tightening and fixing, the pressure receiving portion 7 of the diaphragm 2 is distorted, the zero point position fluctuates, and accurate pressure measurement cannot be performed. In particular, when the position of the overhanging portion 3 approaches the pressure receiving portion 7 for downsizing of the pressure sensor, the amount of fluctuation of the zero point position increases.

Further, in order to ensure the reliability of the pressure seal, the outer peripheral surface of the diaphragm 2 and the inner peripheral surface of the casing 1 must be accurately kept parallel to each other. However, since the fixed nut 5 having a threaded portion is used,
When the fixing nut 5 is tightened, the diaphragm 2 tends to tilt, and the reliability of the pressure seal becomes low.

According to the pressure sensor shown in FIG. 18, almost no external force acts on the diaphragm 15 at the time of mounting, and the pressure receiving portion 19 of the diaphragm 15 is not distorted. But,
When the pressure of the fluid is applied from the upper surface side of the diaphragm 15, the upper O-ring 16 is directly applied with the pressure, and elastic deformation is repeated, which causes a problem of rapid deterioration.

The lower surface of the diaphragm 15 is a surface that comes into contact with other members during manufacturing and transportation, and is easily scratched. Therefore, it is not appropriate to set such a surface as the place where the O-ring 17 is provided.

O-ring 17 on the lower surface side of diaphragm 15
Since it does not undergo the severe elastic deformation unlike the O-ring 16 on the upper surface side, the durability is secured. However, strain gauge 20
Since the O-ring 17 exists around the surface forming the bridge, the conductive wire for extracting the bridge output may come into contact with the O-ring 17, and the degree of freedom in designing the bridge circuit pattern is limited.

Further, when an attempt is made to seal the lower surface of the diaphragm 15 on which the strain gauge 20 is formed with a protective cap or the like in order to protect it from the intrusion of foreign matter such as moisture from the outside, the sealing surface of the protective cap is the pressure receiving portion. It becomes the upper surface of 19. Then, the pressure receiving portion 19 of the diaphragm 15 is distorted by the attachment of the protective cap.

Therefore, the invention according to claim 1 provides a pressure sensor capable of preventing the pressure receiving portion of the diaphragm from being distorted when the diaphragm is mounted in the pressure vessel, and performing highly accurate pressure measurement.

Further, the invention according to claim 2 provides a pressure sensor capable of easily mounting the diaphragm in the pressure vessel.

Further, the invention according to claim 3 provides a pressure sensor capable of easily attaching and detaching the diaphragm mounted in the pressure vessel.

According to the invention of claim 4, when a protective cap for protecting the strain detecting portion is attached to the diaphragm,
Provided is a pressure sensor capable of preventing the pressure receiving portion from being distorted by mounting a protective cap.

[0018]

According to the first aspect of the present invention,
In a pressure sensor having a diaphragm having a strain detecting portion in a pressure receiving portion and a pressure vessel having the diaphragm attached, a flange-shaped protruding portion is formed on an outer peripheral portion of the diaphragm, and the protruding portion engages with a minute gap. An engagement recess was formed in the inner peripheral portion of the pressure vessel, and an O-ring was provided between the inner peripheral surface of the engagement recess and the outer peripheral surface of the overhanging portion.
Therefore, it is possible to prevent the pressure receiving portion of the diaphragm from being distorted when the diaphragm is mounted in the pressure vessel, and it is possible to perform accurate pressure measurement.

According to a second aspect of the invention, in the first aspect of the invention, pressure is applied by a container body having an insertion portion for inserting the diaphragm and a lid portion attached to an end of the container body on the insertion side of the diaphragm. An engaging wall formed on the container body so as to form a container and mount one end surface of the overhang portion, and an engaging wall portion formed on the lid portion so as to face the other end surface of the overhang portion. And were opposed to form an engaging recess. Therefore, it is possible to provide a pressure sensor that can easily attach the diaphragm to the pressure container.

According to a third aspect of the present invention, in the first aspect of the invention, a pair of engaging walls are opposed to each other to form an engaging recess, and at least one of the engaging walls is an inner peripheral portion of the pressure vessel. It is detachably attached to. Therefore, the diaphragm attached to the pressure vessel can be easily attached and detached.

According to a fourth aspect of the present invention, in the first, second or third aspect of the present invention, a protective cap for covering the strain detecting portion is provided, and the joint portion is provided on the outer peripheral portion of the diaphragm below the pressure receiving portion. Was formed, and the protective cap was joined to this joint. Therefore, when the protective cap that protects the strain gauge bridge circuit provided in the pressure receiving portion is attached to the diaphragm, it is possible to prevent the pressure receiving portion from being distorted due to the attachment of the protective cap.

[0022]

FIG. 1 shows a first embodiment of the present invention.
7 will be described with reference to FIG. FIG. 1 is a vertical sectional front view showing a pressure sensor in which a diaphragm 22 is attached inside a pressure vessel 21, and FIG. 2 is a plan view of the pressure sensor. As shown in FIG. 2, the pressure vessel 21 is made up of divided vessels 21a and 21b which are divided into left and right halves.
The pressure vessel 21 is formed by bonding or welding a and 21b at the joint surface 21c. At the time of this bonding or welding, the pressure sensor is completed by mounting the diaphragm 22 to which the protective cap described later is bonded or welded in the pressure vessel 21.

A threaded portion 23 for attaching the pressure sensor to an object to be measured (not shown) is formed on the outer peripheral portion of the pressure vessel 21 on the lower end side. A pressure introducing hole 24 for guiding the pressure of the fluid to be measured to the diaphragm 22 is formed inside the pressure vessel 21.

The diaphragm 22 is formed of a metal material such as duralumin, aluminum, or stainless in a cylindrical shape, and has a thin plate-shaped pressure receiving portion 25 at one end thereof which is distorted when a fluid pressure is applied. As shown in FIG. 3, an insulating film 26 made of an organic material such as polyimide resin is formed on the surface of the diaphragm 22 including the pressure receiving portion 25 on one end side, and the insulating film 26 is formed on the insulating film 26 as shown in FIG. A strain gauge bridge circuit 27, which is a strain detector, is formed, and a protective film 28 for protecting the strain gauge bridge circuit 27 is formed on the strain gauge bridge circuit 27 with an organic material such as a polyimide resin. A conductive wire 29 is connected to the strain gauge bridge circuit 27.

On the outer peripheral portion of the diaphragm 22 on the other end side, a flange-shaped projecting portion 3 is shown enlarged in FIGS. 5 and 6.
Form 0. Engagement recess 32 with which the overhanging portion 30 engages with a minute gap 31 on the inner peripheral portion of the pressure vessel 21.
To form The engagement recess 32 is formed by the pair of engagement walls 3.
3, 34 are formed facing each other. Engagement wall parts 33, 34
The width dimension "L" of the engaging concave portion 32 and the width dimension "W" of the overhanging portion 30 facing each other are set to "L≥W".

An O-ring rectangular groove 35 is formed on the outer peripheral surface of the projecting portion 30, and an O-ring is formed in the O-ring rectangular groove 35.
Attach the ring 36. The attached O-ring 36 is brought into contact with the inner peripheral surface of the engaging recess 32.

A protective cap 37 for protecting the strain gauge bridge circuit 27 from external moisture or the like is bonded to the diaphragm 22 by adhesion or welding. The protective cap 37 is joined to the diaphragm 22 at a joint portion 38 formed below the surface of the pressure receiving portion 25 on the outer peripheral portion of the diaphragm 22. The protective cap 37 is formed with a hole 37a through which the conductive wire 29 is inserted, and after the conductive wire 29 is inserted, the hole 37a is closed with resin.

The strain gauge bridge circuit 27 will be described. This strain gauge bridge circuit 27 is shown in FIGS.
As shown in, the strain gauge patterns 39a to 39d,
Zero balance adjustment patterns 40a and 40b, span temperature correction pattern 41, and zero point temperature correction pattern 42
a, 42b, lead wiring patterns 43a to 43f,
It is composed of lead terminals 44a to 44d.

The procedure for forming the strain gauge bridge circuit 27 is as follows.
As shown in FIG. 3, after the insulating film 26 is formed on the surface of the diaphragm 22 on one end side including the pressure receiving portion 25, a NiCrSi layer and a Ti film are formed on the insulating film 26 by a thin film technique.
A layer and a Cu layer are sequentially formed. After that, the strain gauge patterns 39a to 3a are formed on the NiCrSi layer by the etching technique.
9d and zero balance adjustment patterns 40a and 40b are formed, a span temperature correction pattern 41 and zero point temperature correction patterns 42a and 42b are formed on the Ti layer, and lead wiring patterns 43a to 43f and lead terminals 44a to 44a on the Cu layer.
44d. After forming each of these patterns, the protective film 28 is formed.

With respect to the strain gauge patterns 39a to 39d, compressive stress acts on the strain gauge patterns 39a and 39b located on the outside, and extension stress acts on the strain gauge patterns 39c and 39d located on the inside. The resistance values of the strain gauge patterns 39a and 39b and the resistance values of the strain gauge patterns 39c and 39d are set to be equal. The conductive wire 29 is connected to the lead terminals 44a to 44d by soldering or the like.

In such a structure, the protective cap 3
When the diaphragm 22 to which 7 is joined is mounted in the pressure vessel 21, the overhanging portion 3 of the diaphragm 22 is fitted into the engagement recess 32 of one of the divided vessels 21a which is divided into two.
By engaging 0 and joining the other divided container 21b to this divided container 21a, the overhanging portion 30 is also engaged with the engaging recess 32 of the divided container 21b. After the divided containers 21a and 21b are joined to each other so that the overhanging portion 30 of the diaphragm 22 is engaged with the engaging recess 32 of the divided containers 21a and 21b, the divided containers 21a and 21b are bonded or welded at the joint surface 21c to apply pressure. Complete the sensor.

When the diaphragm 22 is mounted in the pressure vessel 21, since there is a minute space 31 between the overhanging portion 30 and the engaging recess 32, the overhanging portion 30 is not pressed by the engaging recess 32, and the diaphragm 22 is attached to the diaphragm 22. On the other hand, no external force acts on the pressure receiving portion 25, and no strain occurs in the pressure receiving portion 25. Therefore, the pressure receiving portion 25 of the diaphragm 22 is not distorted and the zero point position of the strain gauge bridge circuit 27 does not change before the pressure measurement, and the pressure measurement of the fluid by the pressure sensor can be performed accurately.

The protection cap 37 is joined to the diaphragm 22 by a joint portion 38 formed at a position separated downward from the pressure receiving portion 25. Therefore, the effect of joining the protective cap 37 does not act on the pressure receiving portion 25, and the joining of the protective cap 37 does not cause distortion in the pressure receiving portion 25.

FIG. 6 shows a state in which the fluid pressure is not acting on the diaphragm 22, and FIG. 7 is a state in which the fluid pressure “P” is acting on the diaphragm 22 through the pressure introducing hole 24. When this pressure "P" acts on the lower surface of the pressure receiving portion 25, strain is generated in the strain gauge patterns 39a to 39d of the strain gauge bridge circuit 27 formed on the upper surface of the pressure receiving portion 25, and the electrical resistance changes. Then, by detecting this change in electrical resistance with an external circuit connected by the conductive wire 29,
The pressure of fluid can be measured.

During this pressure measurement, the pressure is transmitted to the O-ring 36 through the minute gap 31, and the pressure is sealed by the self-sealing action of the O-ring 36. Therefore, the presence of this minute gap 31 moderates the pressure change acting on the O-ring 36, and the O-ring 36 is not subjected to severe elastic deformation, so that the durability is improved.

Next, a second embodiment of the present invention will be described with reference to FIG.
It will be described based on. The same parts as those in the first embodiment described above are designated by the same reference numerals, and different points will be described (the same applies hereinafter). In the pressure sensor of the present embodiment, the pressure container 45 is formed by the container body 45a and the lid portion 45b that is bonded or welded to the container body 45a. The container body 45a has an inner diameter dimension slightly larger than the outer dimension of the diaphragm 22 and forms an insertion portion 46 into which the diaphragm 22 is inserted from above. The insertion portion 46 is formed with a bottom surface portion 47 which is a wall portion for engagement on which the lower end surface of the overhang portion 30 is placed when the diaphragm 22 is inserted. The lid 45b is attached to the container main body 4
An upper surface portion 48 that is an engaging wall portion that faces the upper end surface of the protruding portion 30 when attached to the 5a is formed. By making the bottom surface portion 47 and the upper surface portion 48 face each other, an engaging recess 49 is formed in which the projecting portion 30 engages with a minute gap 31.

The width dimension "L" of the engaging recess 49 in which the bottom surface portion 47 and the top surface portion 48 are opposed to each other and the width dimension "W" of the overhang portion 30 are "L≥W". .

In such a structure, the diaphragm 2
When mounting 2 into the pressure container 45, the diaphragm 22 is inserted from above into the insertion portion 46 of the container body 45a to which the lid portion 45b is not mounted, and the lower end surface of the overhang portion 30 is placed on the bottom surface portion 47. After that, the lid portion 45b is adhered or welded to the container body 45a, and the overhanging portion 30 is engaged with the engagement recess 49 in which the bottom surface portion 47 and the top surface portion 48 are opposed to each other.

When the diaphragm 22 is mounted in the pressure container 45, the overhanging portion 30 engages with the engaging recess 49 with the minute gap 31, so that the overhanging portion 30 is not pressed by the engaging recess 49, and is opposed to the diaphragm 22. As a result, no external force acts, and the pressure receiving portion 25 is not distorted. Therefore, the zero point position of the strain gauge bridge circuit 27 does not fluctuate before the pressure measurement due to the strain in the pressure receiving portion 25 of the diaphragm 22, and the accuracy of the fluid pressure measurement is high when this pressure sensor is used. Can measure pressure.

In this pressure sensor, the diaphragm 22 is attached to the pressure container 45 by using the insertion portion 4 of the container body 45a.
It is performed by inserting the diaphragm 22 into 6 and adhering or welding the lid portion 45b to the container body 45a after the insertion. Therefore, the work of attaching the diaphragm 22 to the pressure container 45 can be easily performed, and the productivity of the pressure sensor is increased.

Next, a third embodiment of the present invention will be described with reference to FIG.
It will be described based on. The pressure sensor of this embodiment has the same basic structure as the pressure sensor of the second embodiment. The different point is that the container body 45a and the lid portion 45b are connected by a screw portion 45c.

In such a structure, the diaphragm 2
When attaching 2 to the pressure container 45, the diaphragm 22 is inserted from above into the insertion portion 46 of the container body 45a from which the lid portion 45b is removed, and the lower end surface of the overhang portion 30 is placed on the bottom surface portion 47. Then, the lid 45b and the container body 45
a is connected by a screw portion 45c, and a bottom surface portion 47 and an upper surface portion 48 are connected.
The projecting portion 30 is engaged with the engaging recessed portion 49 in which and are opposed to each other.

When the diaphragm 22 is attached to the pressure container 45, the diaphragm 2 is inserted into the insertion portion 46 of the container body 45a.
2 is inserted, and the lid 45b is screwed to the container body 45a after the insertion. Therefore, the work of attaching the diaphragm 22 to the pressure container 45 can be easily performed, and the productivity of the pressure sensor is increased.

In the present embodiment, the container body 45a and the lid portion 45b are connected by the screw portion 45c, so that the diaphragm 22 can be easily replaced. Also, the container body 4
By connecting the screw 5c and the lid 45b to each other 5a, the strength of the screw 45c is increased, and the connection between the container body 45a and the lid 45b does not come off even when a high pressure is applied.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
0 and FIG. 11 will be described. In the pressure sensor of the present embodiment, a pressure container 50 having an integral structure is provided, and the diaphragm 22 is mounted in the pressure container 50. An insert portion 51 having an inner diameter slightly larger than the outer dimension of the diaphragm 22 is formed in the pressure container 50, and a C ring 52 as an engaging wall portion is detachably attached to the inner peripheral surface of the insert portion 51. A possible mounting groove 53 is formed. Then, the C ring 52 attached to the attachment groove 53 and the bottom surface portion 54 of the insertion portion 51, which is the engagement wall portion, are opposed to each other, and the engagement recess 55 is formed.
To form

The width dimension "L" of the engaging recess 55 and the width dimension "W" of the overhanging portion 30 in which the C ring 52 mounted in the mounting groove 53 and the bottom surface portion 54 are opposed to each other are described above. As in the above embodiment, “L ≧ W” is set.

In such a structure, the diaphragm 2
2 is installed in the pressure vessel 50, the C ring 52
Is removed from the mounting groove 53, the diaphragm 22 is inserted into the insertion portion 51 from above, and the lower surface of the diaphragm 22 is placed on the bottom surface portion 54. After that, the C ring 52 is mounted in the mounting groove 53, so that the projecting portion 30 is engaged with the engaging recess 55 in which the bottom surface portion 54 and the C ring 52 are opposed to each other.

When the diaphragm 22 is mounted in the pressure vessel 50, the overhanging portion 30 engages with the engaging recess 55 with the minute gap 31, and the overhanging portion 30 is not pressed by the engaging recess 55, and is opposed to the diaphragm 22. No external force acts,
No distortion occurs in the pressure receiving portion 25. Therefore, the diaphragm 2
The zero point position of the strain gauge bridge circuit 27 does not fluctuate before the pressure measurement due to strain in the pressure receiving portion 25 of No. 2, and accurate pressure measurement can be performed when the fluid pressure is measured by this pressure sensor. You can do it.

In this pressure sensor, the C ring 52 can be removed from the mounting groove 53. When the C ring 52 is removed from the mounting groove 53, the engagement of the overhanging portion 30 with the engagement recess 55 is released, and the diaphragm 22 can be removed from the insertion portion 51. Therefore, the diaphragm 22 can be easily replaced.

Next, a fifth embodiment of the present invention will be described with reference to FIG.
2 and FIG. In the pressure sensor of the present embodiment, the pressure vessel 56 is formed by fastening the divided vessels 56a and 56b that are vertically divided by bolts 57 and nuts 58. On the lower end side of the upper divided container 56a, an insertion portion 59 having an inner diameter larger than the outer dimension of the diaphragm 22 is formed. The pressure introducing hole 24 is formed in the lower divided container 56b.

The inner peripheral surface of the insertion portion 59 is an engagement wall portion with which the upper surface of the overhanging portion 30 of the diaphragm 22 abuts when the diaphragm 22 is inserted from the lower end side opening portion of the insertion portion 59. The step portion 60 is formed. In addition, a mounting groove 62 is formed on the inner peripheral surface of the insertion portion 59 so that the C-ring 61, which is an engaging wall portion, can be removably mounted. And
The C-ring 61 mounted in the mounting groove 62 and the step portion 60 are opposed to each other to form an engaging recess 63.

The width dimension "L" of the engaging recess 63 in which the C ring 61 mounted in the mounting groove 62 and the step portion 60 are opposed to each other and the width dimension "W" of the overhang portion 30 of the diaphragm 22 are As in the above-described embodiment, “L ≧
W ".

In such a structure, the diaphragm 2
2 is installed in the pressure vessel 56, the divided vessel 56
a and 56b are divided, the C ring 61 is removed from the mounting groove 62, and the diaphragm 22 is inserted into the insertion portion 59.
Insert from the lower end side of a. After the upper surface of the overhanging portion 30 is inserted to a position where it abuts on the step portion 60, the C ring 61 is attached to the attachment groove 62, whereby the step portion 60 and the C ring 6 are attached.
The overhanging portion 30 is engaged with the engaging recessed portion 63 that is opposed to 1. After that, the divided containers 56a and 56b are tightened and fixed using the bolts 57 and the nuts 58 to complete the pressure sensor.

When the diaphragm 22 is mounted in the pressure vessel 56, the overhanging portion 30 engages with the engaging recess 63 with the minute gap 31, so that the overhanging portion 30 is not pressed by the engaging recess 63 and is attached to the diaphragm 22. As a result, no external force acts, and the pressure receiving portion 25 is not distorted. Therefore, the zero point position of the strain gauge bridge circuit 27 does not fluctuate before the pressure measurement due to the strain in the pressure receiving portion 25 of the diaphragm 22, and the accuracy of the fluid pressure can be measured when this pressure sensor is used. Can perform good pressure measurement.

Next, a sixth embodiment of the present invention will be described with reference to FIG.
4 will be described. The pressure sensor of the present embodiment is
An insertion portion 65 having an inner diameter slightly larger than the outer dimension of the diaphragm 22 is formed in the pressure container 64, and a pair of C rings 6 as engagement walls are formed on the inner peripheral surface of the insertion portion 65.
A pair of mounting grooves 68, 6 in which 6, 67 can be detachably mounted
9 is formed. And C attached to the attachment grooves 68, 69
Engagement recesses 70 are formed by opposing the rings 66 and 67.

C ring 6 mounted in the mounting grooves 68, 69
The width dimension “L” of the engaging recessed portion 70 in which 6, 67 are opposed to each other,
The width dimension “W” of the overhang portion 30 of the diaphragm 22 is
As in each of the above-described embodiments, “L ≧ W”.

In such a structure, the diaphragm 2
When mounting 2 in the pressure vessel 64, the lower C ring 67 is mounted in the mounting groove 69, the diaphragm 22 is inserted into the insertion portion 65 from above, and the lower surface of the diaphragm 22 is placed on the C ring 67. . Then, by attaching the C ring 66 to the attachment groove 68, the pair of C rings 66,
The projecting portion 30 is engaged with the engaging concave portion 70 facing 67.

When the diaphragm 22 is mounted in the pressure vessel 64, the overhanging portion 30 engages with the engaging recess 70 with the minute gap 31, so that the overhanging portion 30 is not pressed by the engaging recess 70, and is opposed to the diaphragm 22. As a result, no external force acts, and the pressure receiving portion 25 is not distorted. Therefore, the pressure receiving portion 25 of the diaphragm 22 is not distorted and the zero point position of the strain gauge bridge circuit 27 does not change before the pressure measurement, and the pressure measurement of the fluid by the pressure sensor can be performed accurately.

In this pressure sensor, the C rings 66 and 67 are used.
Can be removed from the mounting grooves 68, 69. One C
When the ring 66 is removed from the mounting groove 68, the engagement of the overhang portion 30 with the engagement recess 70 is released, and the diaphragm 2
2 can be removed from the insertion portion 65. Therefore, the diaphragm 22 can be easily replaced.

Next, a seventh embodiment of the present invention will be described with reference to FIG.
5 will be described. The basic structure of the pressure sensor of this embodiment is the same as that of the fourth embodiment shown in FIGS. 10 and 11. The difference is that in the fourth embodiment, the O-ring rectangular groove 35 is formed on the outer peripheral surface of the overhanging portion 30 and the O-ring 36 is mounted, whereas in the present embodiment, the inner peripheral surface of the engaging recess 55 is different. The point is that an O-ring rectangular groove 35a is formed on the surface, an O-ring 36 is mounted in the O-ring rectangular groove 35a, and the mounted O-ring 36 is brought into contact with the outer peripheral surface of the overhang portion 30.

With this structure, in the present embodiment as well as in the fourth embodiment, when the diaphragm 22 is mounted in the pressure vessel 50, the overhanging portion 3 is formed.
0 is not pressed by the engaging recess 55, and the pressure of the fluid can be measured with high accuracy. Further, the diaphragm 22 can be easily replaced by removing the C ring 52 from the mounting groove 53.

Next, an eighth embodiment of the present invention will be described with reference to FIG.
6 will be described. In the present embodiment, the measured object 71 through which the fluid flows is used as a pressure container. As in the second embodiment shown in FIGS. 10 and 11, an insertion portion 72 having an inner diameter slightly larger than the outer dimensions of the diaphragm 22 is formed in the measured object 71, and the insertion portion 72 is formed. A mounting groove 74 is formed on the inner peripheral surface of which the C-ring 73, which is an engaging wall, can be removably mounted. Then, the C-ring 73 attached to the attachment groove 74 and the bottom surface portion 75 of the insertion portion 72, which is the engagement wall portion, are opposed to each other to form an engagement recess 76.

In such a structure, the diaphragm 2
2 is mounted inside the object to be measured 71, the C ring 73
Is removed from the mounting groove 74, the diaphragm 22 is inserted into the insertion portion 72 from above, and the lower surface of the diaphragm 22 is placed on the bottom surface portion 75. After that, the C ring 73 is attached to the attachment groove 74, so that the overhanging portion 30 is engaged with the engaging recess 76 in which the bottom surface portion 75 and the C ring 73 are opposed to each other.

When the diaphragm 22 is attached to the inside of the object to be measured 71, the overhanging portion 30 engages with the engaging recessed portion 76 with the minute gap 31, so that the overhanging portion 30 is not pressed by the engaging recessed portion 76 and is attached to the diaphragm 22. On the other hand, no external force acts on the pressure receiving portion 25, and no strain occurs in the pressure receiving portion 25. Therefore, the pressure receiving portion 25 of the diaphragm 22 is not distorted and the zero point position of the strain gauge bridge circuit 27 does not change before the pressure measurement, and the pressure measurement of the fluid by the pressure sensor can be performed accurately.

In this pressure sensor, the C ring 73 can be removed from the mounting groove 74. When the C ring 73 is removed from the mounting groove 74, the engagement of the overhanging portion 30 with the engagement recess 76 is released, and the diaphragm 22 can be removed from the insertion portion 72. Therefore, the diaphragm 22 can be easily replaced.

In each of the above-mentioned embodiments, the C-rings 52, 61, 66, 6 are used as the detachable engagement wall portions.
Although the case of using 7, 73 is described as an example, an E ring may be used instead of the C ring.

[0067]

According to the first aspect of the present invention, it is possible to prevent the pressure receiving portion of the diaphragm from being distorted when the diaphragm is mounted in the pressure vessel, and it is possible to perform highly accurate pressure measurement.

According to the second aspect of the invention, the work of mounting the diaphragm in the pressure vessel can be easily performed.

According to the third aspect of the invention, the diaphragm mounted in the pressure vessel can be easily attached and detached.

According to the invention described in claim 4, when the protective cap for protecting the strain detecting portion is attached to the diaphragm,
It is possible to prevent the distortion due to the mounting of the protective cap from occurring in the pressure receiving portion.

[Brief description of drawings]

FIG. 1 is a vertical sectional front view showing a pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a plan view thereof.

FIG. 3 is a vertical cross-sectional front view showing a laminated structure on the surface of the diaphragm.

FIG. 4 is a plan view showing the structure of a strain gauge bridge circuit.

FIG. 5 is a bridge circuit diagram.

FIG. 6 is a vertical sectional front view showing a part of the pressure sensor in an enlarged manner.

FIG. 7 is a vertical cross-sectional front view showing an enlarged state when pressure is applied.

FIG. 8 is a vertical sectional front view showing a pressure sensor according to a second embodiment of the present invention.

FIG. 9 is a vertical sectional front view showing a pressure sensor according to a third embodiment of the invention.

FIG. 10 is a vertical sectional front view showing a pressure sensor according to a fourth embodiment of the present invention.

FIG. 11 is a vertical sectional front view showing a part of the device in an enlarged manner.

FIG. 12 is a vertical sectional front view showing a pressure sensor according to a fifth embodiment of the present invention.

FIG. 13 is a vertical sectional front view showing a part of the device in an enlarged manner.

FIG. 14 is a vertical sectional front view showing an enlarged part of the pressure sensor of the sixth embodiment of the invention.

FIG. 15 is a vertical cross-sectional front view showing a part of a pressure sensor of a seventh embodiment of the present invention in an enlarged manner.

FIG. 16 is a vertical sectional front view showing a pressure sensor according to an eighth embodiment of the present invention.

FIG. 17 is a vertical sectional front view showing a conventional pressure sensor.

FIG. 18 is a vertical cross-sectional front view showing another conventional pressure sensor.

[Explanation of symbols]

21, 45, 50, 56, 64, 71 Pressure vessel 22 Diaphragm 25 Pressure receiving part 27 Strain detecting part 30 Overhanging part 31 Micro gap 32, 49, 55, 63, 70, 76 Engagement concave part 33, 34, 47, 48, 52, 54, 60, 61, 6
6, 67, 73, 75 Engaging wall portion 36 O-ring 38 Joining portion 45a Container body 45b Lid portion 46 Inserting portion

Claims (4)

[Claims] 1. A pressure sensor having a tubular diaphragm having a strain detecting portion provided on a pressure receiving portion and a pressure vessel having the diaphragm attached thereto, wherein a flange-like protruding portion is formed on an outer peripheral portion of the diaphragm, and the protruding portion is formed. Forming an engaging recess on the inner periphery of the pressure vessel, the parts engaging with a minute gap,
A pressure sensor comprising an O-ring between an inner peripheral surface of the engagement recess and an outer peripheral surface of the overhang portion. 2. A pressure container is formed by a container main body having an insertion part for inserting a diaphragm and a lid part attached to an end of the container main body on the insertion side of the diaphragm, and one end face of the overhang part is placed on the pressure container. As described above, the engaging wall formed on the container body and the engaging wall formed on the lid so as to face the other end surface of the overhanging portion face each other to form an engaging recess. The pressure sensor according to claim 1. 3. A pair of engaging wall portions are opposed to each other to form an engaging concave portion, and at least one engaging wall portion is detachably attached to the inner peripheral portion of the pressure vessel. The pressure sensor described. 4. A protective cap for covering the strain detecting portion is provided, a joint portion is formed on an outer peripheral portion of the diaphragm below the pressure receiving portion, and the protective cap is joined to the joint portion. The pressure sensor according to claim 1, 2 or 3.