JPS5831855B2 - Manufacturing method of pressure measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a pressure measuring device that measures a difference between a pressure to be measured and a reference pressure or a difference between another pressure to be measured using a metal measuring diaphragm.

In pressure measuring devices that measure differential pressure by changes in capacitance, a measuring diaphragm is typically joined to the peripheral edge of a bottomed metal cylindrical housing by welding.

However, this differential pressure measuring device has the problem that the measuring diaphragm undergoes abnormal thermal deformation and distortion due to the high heat during welding, making it impossible to obtain an output signal that is accurately proportional to the differential pressure. Ta.

Therefore, the applicant proposed a pressure measuring device that eliminates the distortion of the measuring diaphragm caused by high heat during welding.

This pressure measuring device uses, as a measuring diaphragm, a diaphragm molded from a precipitation hardening metal that has high elasticity and shrinks through heat treatment (for example, the product name Elinvar-1, the product name Themerast, and the product name Nickel Spun C). It is characterized by the use of

After the measuring diaphragm made of such a precipitation-hardened metal is connected to the housing by welding,
The measurement diaphragm is heat treated.

Then, the measurement diaphragm shrinks in volume due to the heat treatment, and shrinkage stress is generated.

This shrinkage stress removes the strain on the measuring diaphragm that occurs during welding.

However, as a result of various experiments and research conducted by the present inventors, in addition to the advantage that this method can eliminate the distortion of the measurement diaphragm that occurs during welding, it also has the following disadvantages: That is, the heat treatment is performed at a high temperature, e.g.
℃, the housing and the insulator provided within the housing undergo abnormal thermal deformation, and it has been found that this deformation causes stress on the measuring diaphragm that is undesirable in terms of measurement accuracy. did.

This stress will be explained with reference to FIG.

In FIG. 1, a pressure measuring device 1 includes first and second housings 2 and 3 each having a cylindrical shape with a bottom, and a measuring diaphragm having an insulating portion sandwiched between the housings 2 and 3 and connected by welding. 4, and first and second insulators 5 coupled to the inner surfaces of the first and second housings 2 and 3.
, 6.

These insulators 5 and 6 form a spherical wall surface 7°8 on the side facing the measurement diaphragm 4, and metal foils 9 and 1
Set 0.

Together with the measuring diaphragm 4, these metal foils 9 and 10 constitute the electrodes of the variable capacitor.

In addition, the walls 7 and 8 of the measurement diaphragm 4 and the insulators 5 and 6
A space 11, 12 is provided between the two, and different pressures to be measured are introduced through the pressure guiding holes 13, 14, respectively.

This measuring diaphragm 4 is made of precipitation hardening metal (for example, trade names: Elinva, Thermelas, Elgiloy, Nickel Spun C, KRN, etc.), and is heat-treated at a high temperature, for example, about 500°C to 600°C for about 1 hour. When this is done, intermetallic compounds precipitate within the crystal, causing the volume to shrink.

Therefore, after joining the peripheral edge of the measuring diaphragm 4 to the peripheral edges of the first and second housings 2 and 3 by welding,
When the measuring diaphragm 4 is heat-treated, a uniform shrinkage stress is generated in the measuring diaphragm 4 due to contraction, and this shrinkage stress removes the strain generated during the welding operation of the diaphragm 4.

At this time, the material of the first and second insulators 5 and 6 coupled to the inner surfaces of the first and second housings 2 and 3 is approximately 500%
A material that can withstand high heat treatment temperatures of ℃ to 600 ℃ and has a thermal expansion value relatively close to that of the metal of these housings 2 and 3 is selected, such as porcelain (ceramic) such as fullsterite and alumina. has been adopted.

This porcelain insulator 5,6 is usually connected to the metal housing 2,3.
It is baked on the inner surface at a high temperature of about 700'C to 800C.

FIG. 2 shows a thermal expansion diagram of metal and porcelain.

In the figure, characteristic line A is the thermal expansion characteristic of metal, and characteristic line B is the thermal expansion characteristic of porcelain.

As can be seen from this figure, metals and porcelain have essentially different thermal expansion characteristics, and the metals used in this type of differential pressure measuring device have a smaller coefficient of thermal expansion than porcelain in low-temperature regions, and in high-temperature regions. It has a larger coefficient of thermal expansion than porcelain.

FIG. 3 shows an explanatory diagram for explaining thermal expansion during heat treatment of the pressure measuring device in FIG. 1.

In the figure, parts having the same functions as in FIG. 1 are designated by the same reference numerals.

Now, when the pressure measuring device is heated to the heat treatment temperature of the precipitation hardened metal measuring diaphragm 4, for example, 600°C, the amount of thermal expansion in the bottom portions 17, 18 of the metal housings 2, 3 will be explained in FIG. As mentioned above, the thermal expansion characteristic line A of metal
Accordingly, at high temperatures metal has a larger coefficient of thermal expansion than porcelain, so the thermal expansion in the region of the cylindrical part 15.16 forming the magnetic-metal composite with the porcelain insulator 5.6 inside. Since the amount of thermal expansion is intermediate between the thermal expansion characteristic line A of metal and the thermal expansion characteristic line B of porcelain at a heat treatment temperature of 600° C., it is larger than the amount of thermal expansion in the area of the cylindrical portion 15.16.

For this reason, the pressure measuring device 1 undergoes thermal expansion as shown by the dotted line and bends in the direction of the arrow, resulting in thermal deformation similar to a bimetallic effect.

This thermal deformation causes permanent deformation in the first and second housings 2,3.

Due to this deformation, the characteristics of the measurement diaphragm 4 could not be stabilized.

Furthermore, when the insulators 5 and 6 are baked into the housings 2 and 3, thermal deformation occurs in the direction indicated by the arrows as described above, which causes the insulators 5 and 6 to be damaged.
, 6, there was also a risk of causing defective printing.

In view of the above-mentioned points, it is an object of the present invention to provide a pressure measuring device capable of applying a stable and uniform tension to a measuring diaphragm without the drawbacks of the prior art.

Another object of the present invention is to provide a pressure measuring device in which the baking operation of the insulator is improved and production efficiency is improved.

According to the present invention, such an object is achieved by providing first and second housings each having a bottomed cylindrical shape having a through hole at the bottom, and a protrusion on one side surface, which protrusion is connected to the first and second housings. cylindrical first and second insulators that are coupled to the bottom through holes of the two housings and have outer diameters smaller than inner diameters of the cylindrical portions of the first and second housings; a measuring diaphragm made of a precipitation-hardened metal that is held between the housing and connected to the peripheral edges of the first and second housings by welding, has high elasticity, and is contracted by heat treatment; Said first and second
This is accomplished by heat treatment after bonding to the housing.

In addition, in the present invention, the first and second housings and the first
and the material of the second insulator.

Next, embodiments of the present invention will be described in detail based on the drawings.

FIG. 4 shows a schematic configuration diagram of an embodiment of the present invention, in which A is a front sectional view and B is a sectional view of A in the XX direction.

In the figure, parts having the same functions as those in FIGS. 1 and 3 are given the same reference numerals.

The pressure measuring device 21 includes a measuring diaphragm 4 mainly made of a precipitation-hardened metal that has high elasticity and shrinks when subjected to heat treatment, first and second housings 22,
23, and first and second insulators 24 and 25 connected to the spaces of these housings 22 and 23.

The first and second housings 22 and 23 are cylindrical bodies with bottoms,
A through hole 34.35 is provided in the center of the bottom 32.33.

Further, the first and second insulators 24 and 25 are cylindrical bodies, and protrusions 36 and 37 are formed on one side surface.

This protrusion 36,37 is connected to the first and second housing 22.
They are connected only at the inner surfaces of the through holes 34 and 35 in the bottom parts 32 and 33 of .

The bonding is performed by brazing when the insulators 24 and 25 are made of porcelain, and by baking when they are made of glass.

Further, the outer diameter of the cylindrical portion 28.29 is smaller than the inner diameter of the cylindrical portion 26.27 of the first and second housings 22.23 to form a cylindrical groove 30.31.

Note that the grooves 38 and 39 of the first and second insulators 24 and 25
are the bottom parts 32, 3 of the first and second housings 22, 23.
3 and communicates with the grooves 30 and 31.

Now, when aging the pressure measuring device 1,
Housing 22.23 Shield, first and second insulators 24.
First, consider the thermal expansion that occurs between the through holes 34 and 35 and the protrusions 36 and 37 as the thermal expansion due to the difference in materials between the through holes 34 and 25.

Inner diameter and depth of through hole 34.35 and protrusion 36.37
The outer diameter and width of the through hole 34, 35 and the protrusion 3 are made small, and the joint area between the through hole and the protrusion 3 is made small.
6°31, and the first and second
Between the cylindrical parts 26 and 27 of the housings 22 and 23 and the cylindrical parts 28 and 29 of the first and second insulators 24 and 25,
Since the cylindrical groove 30.31 is formed to eliminate the fixed connection between the cylindrical part 26.27 and the cylindrical part 28.29, even if the thermal expansion of the housing 22.23 and the insulator 24.25 is different, The difference in the amount of thermal expansion is small.

In this embodiment, the outer diameter of the housing 22,23 is approximately 5
0M, and the inner diameter of the through holes 34 and 35 is approximately 8w1. The depth is approximately 3 cm.

Furthermore, since the cylindrical portions 26 and 27 and the cylindrical portions 28 and 29 have the intervening cylindrical grooves 30 and 31, they each thermally expand independently and are not affected by each other, so thermal deformation as shown in Fig. 3 does not occur. .

Therefore housing 22.23 with measuring diaphragm 4
A measuring diaphragm 4 with stable characteristics can be obtained without causing torsional deformation on the contact surface.

At this time, if the material of these insulators 24.25 is selected so that its thermal expansion is approximately equal to that of the material of the housing 22.23 at the baking temperature, the through hole 34.3 with a small inner diameter can be formed.
5 and the protrusions 36 and 37 having a small outer diameter, the baking operation is performed, so damage due to poor baking can be prevented.

As described above, according to the present invention, the through hole at the bottom of the bottomed cylindrical housing is fixedly coupled only to the protrusion of the cylindrical insulator, and the insulator is joined to the housing. By providing a cylindrical groove between the cylindrical part and the cylindrical part of the insulator, when the pressure measuring device is heated to the heat treatment temperature, the housing bends like the bimetallic effect that conventionally occurs due to thermal expansion. The effects are extremely significant, such as a stable and uniform tension being applied to the measuring diaphragm without thermal deformation, and furthermore, poor bonding when bonding the insulator to the housing is improved, and production efficiency is improved.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a conventional example of a pressure measuring device, Fig. 2 is a thermal expansion diagram of metal and porcelain, Fig. 3 is an explanatory diagram of thermal expansion of the pressure measuring device in Fig. 1, and Fig. 4 1 is a schematic configuration diagram of an embodiment of the present invention, A is a front sectional view, and B is a XX sectional view of A. 21... Pressure measuring device, 22, 23...
・Housing, 4... Measuring diaphragm, 2
4,25...Insulator, 26,2T...
Cylindrical part, 28, 29... Cylindrical part, 30, 31
...Groove, 32, 33...Bottom, 34,
35...Through hole, 36, 37...Protrusion, 38, 39...Groove.

Claims (1)

[Claims] 1. First and second housings each having a bottomed cylindrical shape having a through hole at the bottom, and a protrusion on one side thereof, the protrusion being coupled to the bottom through hole of the first and second housings. , an outer diameter is formed smaller than an inner diameter of the cylindrical portion of the first and second housings, and the first
and a second housing, and a cylindrical first and second insulator having a cylindrical groove therebetween; and a periphery of the first and second housings, which are sandwiched between the first and second housings, and a peripheral edge of the first and second housings. a pressure to be measured that is connected to the first insulator by welding to form a space between the second insulator and the first insulator and introduced into the space through a passage provided in the first insulator;
Another space is formed between the second insulator and the second insulator, and the pressure is generated by a pressure difference between the reference pressure or another measured pressure introduced into the other space through a passage provided in the second insulator. a measuring diaphragm made of a precipitation-hardened metal that electrically measures displacement, has high elasticity, and shrinks upon heat treatment; and after the measuring diaphragm is coupled to the first and second housings, heat treatment is performed. A method of manufacturing a pressure measuring device, characterized by performing the following steps.