JPH09286659A - Ceramic diaphragm and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the diaphragm capable of surely showing a large amount of deflection although it is made of a ceramic material and also to provide an appropriate manufacture of the diaphragm. SOLUTION: This diaphragm 1 has a <=0.75mm thickness and an almost concentric-circular pattern in the plan view and also, the cross section that passes through the center 2 of the diaphragm 1 and is perpendicular to the diaphragm plane, has a wavy shape of a prescribed pitch P and a prescribed amplitude S. In this manufacture, a fired almost circular ceramic thin sheet having a <=0.75mm thickness is interposed between the forming surfaces of a pair of forming molds each provided with an almost concentric-circular forming surface nearly corresponding to the both surfaces of the objective ceramic diaphragm 1 and subjected to superplastic deformation by pressing the ceramic thin sheet at a temp. within the region in which the ceramic thin film shows a superplastic phenomenon, to form the cross section of the ceramic thin sheet into a wavy shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic diaphragm, and more particularly to a ceramic diaphragm used for a pressure sensor element, a diaphragm pump and the like.

[0002]

2. Description of the Related Art Among diaphragms of this type, those used for corrosive fluids include those made of stainless steel or tantalum alloy. However, stainless steel is cheap, but its corrosion resistance is not always sufficient.
Tantalum alloy has excellent corrosion resistance, but is expensive. Under these circumstances, some ceramic diaphragms, which have excellent corrosion resistance and are relatively inexpensive as compared with tantalum alloys, have been put into practical use.

[0003]

However, since ceramic has a larger Young's modulus than metal and less flexural deformation with respect to pressure, it is inferior in pressure responsiveness to a metal diaphragm. Then, in order to secure a large amount of this flexural deformation, it is necessary to reduce the thickness of the diaphragm itself or increase its diameter. On the other hand, if the wall thickness is reduced as described above, the pressure resistance performance is deteriorated. Further, if the diameter is increased, the size of the device itself to which the diaphragm such as the pressure sensor is attached is increased.

The present invention has been devised in view of the above point, and an object thereof is to provide a diaphragm which is a ceramic diaphragm but can secure a large amount of flexural deformation, and a suitable manufacturing method thereof. To provide.

[0005]

In order to achieve the above object, a ceramic diaphragm according to the present invention has a substantially concentric circular shape in plan view, and a cross section passing through the center and perpendicular to the surface is corrugated. Is formed in the. Having a substantially concentric circular shape and having a corrugated cross section that passes through the center and is perpendicular to the plane means that it is formed in a substantially concentric circular ripple shape in plan view. The "waveform" includes a waveform curve formed by repeating a circular arc shape, a triangular shape, a trapezoidal shape, or a shape similar thereto, or a shape similar thereto. The amplitude and pitch of the waveform may be constant from the center toward the outside, or may be gradually increased or gradually decreased.

The ceramic is alumina (Al2 O3
), Zirconia (ZrO2), alumina-zirconia composite (Al2 O3 + ZrO2), silicon nitride (Si3
N4) and the like are exemplified. The diaphragm is suitable to have a wall thickness of 0.05 to 0.75 mm. This is because regardless of the material of the ceramic, it is possible to form by the following superplastic deformation, which is suitable as a manufacturing method, up to this range, but it becomes difficult when the wall thickness is 1.0 mm or more.

The ceramic diaphragm according to the present invention has a substantially concentric circular shape and is formed such that a cross section passing through the center and perpendicular to the surface has a corrugated shape. Since the amount of flexural deformation is larger than that of a ceramic diaphragm, a ceramic diaphragm having excellent pressure response characteristics can be obtained.

The preferred manufacturing method of the diaphragm is a ceramic diaphragm having a substantially concentric circular shape and a cross section passing through the center of the diaphragm and perpendicular to the surface is corrugated. The ceramic diaphragm is fired (sintered). Wall thickness 0.7
A substantially circular ceramic thin plate having a diameter of 5 mm or less is sandwiched between the molding surfaces of two molding dies each having substantially concentric molding surfaces substantially corresponding to both surfaces of the ceramic diaphragm, and the ceramic thin plate is a superplastic phenomenon. The cross section may be formed into a corrugated shape by applying pressure in a temperature range indicated by (1) to cause superplastic deformation.

According to this method, the ceramic thin plate sandwiched between the molding die surfaces of the two molding dies each having substantially concentric molding surfaces substantially corresponding to both surfaces of the ceramic diaphragm is formed by both moldings. When pressure is applied between the mold surfaces, it is superplastically deformed into a shape following the molding surface, that is, a shape corresponding to the molding surface. Here, the superplastic deformation means that the deformation resistance becomes low in a predetermined temperature range, and the ceramic causes slippage at the grain boundary with a relatively low stress to cause a huge elongation without breaking. It is preferable that the fired substantially circular ceramic thin plate has a wall thickness of 0.75 mm or less from the viewpoint of ensuring the bending of the diaphragm and superplastic deformation.

The temperature range in which superplastic deformation is exhibited is a temperature at which plastic deformation is possible without breaking and is different depending on the ceramic, so it may be set according to each. However, in superplastic deformation, the smaller the crystal grain size, the easier the grain boundary slip at high temperature. Further, superplastic deformation is not practical because the forming speed becomes slower as the temperature is lower, but there is significant grain growth at the sintering temperature and the grains become coarser, so superplasticity due to grain boundary slip does not occur, so that Keep below the setting temperature.

The temperature range that exhibits superplastic deformation and the temperature range that is preferable for molding differ depending on each material, but are as follows. That is, in the case of zirconia, it is 1000 to 150.
It is about 0 ° C., preferably about 1200 to 1400 ° C., and in the case of alumina, about 1200 to 1600 ° C., but preferably about 1300 to 1500 ° C., alumina-
In the case of a zirconia composite, it is about 1200 to 1500 ° C., preferably about 1200 to 1400 ° C., and in the case of silicon nitride, it is about 1200 to 1700 ° C., but preferably about 1400 to 1600 ° C. However, the ceramics to which the present manufacturing method can be applied are not limited to these, and can be applied to a material exhibiting superplastic deformation by applying stress in a temperature range exhibiting superplastic deformation.

The pressing force varies depending on the temperature at the time of pressurization, the size of the projected area of the molding die surface in plan view, the material of the fired ceramic thin plate, the wall thickness and the amplitude and pitch of the waveform, but 5 to 50 kgf / It is preferably about cm ² .
The deformation or strain rate increases as the temperature rises, but it may be set within a range that does not cause destruction of the fired ceramic thin plate or a significant decrease in strength. As the mold, a mold having substantially concentric molding surfaces substantially corresponding to both surfaces of the ceramic diaphragm to be molded is used, but the amplitude on the molding surface is larger than the amplitude of the diaphragm obtained by superplastic deformation. It is advisable to increase the pressure by about 5 to 100%, and to adjust the pressurizing stroke of the molding die to obtain the desired amplitude. The material of the mold is selected from heat-resistant materials such as ceramics (alumina, zirconia, alumina-zirconia, silicon nitride, etc.) and heat-resistant alloys, etc. according to the molding temperature so as not to react with the ceramic thin plate. Good.

[0013]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described in detail with reference to FIG. In the figure, 1 is a diaphragm of this example, which has a predetermined diameter and a wall thickness of 0.05.
It is made of a ceramic thin plate (sintered body) with a diameter of up to 0.75 mm, has a concentric circular shape in plan view, and the cross section perpendicular to the plane passing through the center 2 of the circle has a corrugated cross section with a predetermined radius R . The amplitude S and the pitch P of the waveform portion 3 are
Each is set to be constant from the center 2 toward the outside. The outer peripheral edge portion 4 is formed to be flat, so that it can be easily attached to the device. In this embodiment, the cross-sectional shape is an arcuate waveform. However, the cross-sectional shape may be a substantially triangular waveform 13 as shown in FIG. 4 or a substantially trapezoidal waveform 23 as shown in FIG.

Such a diaphragm 1 can also be manufactured by firing a thick ceramic molded body, and then grinding or polishing the ceramic molded body into a desired shape. Also, at the stage of unfired ceramic molded body,
It can be also manufactured by forming a diaphragm shape having a substantially concentric shape and having a corrugated cross section that passes through the center 2 and is perpendicular to the surface, and then fire it. Next, the preferred manufacturing method will be described in detail. .

First, a zirconia ceramic raw material powder containing a predetermined additive such as a binder is mixed, and then a circular ceramic sheet having a predetermined wall thickness of 0.05 to 0.75 mm is formed by a doctor blade method or the like. After molding, degreasing, and firing at a predetermined temperature, a ceramic thin plate (average particle size 0.5 μm) is manufactured. The unsintered ceramic sheet is
The ceramic powder may be produced by sheet molding, but it is not always necessary that the thin plate is a flat plate.

Next, the ceramic thin plate 11 thus formed and fired is formed into a substantially concentric shape substantially corresponding to both surfaces 5 and 6 of the desired ceramic diaphragm 1 as shown in FIGS. Molding surfaces 101 of two molding dies 101 and 102 respectively having molding surfaces 101a and 102a of
It is sandwiched between a and 102a. That is, the ceramic thin plate 11 has a predetermined concentric circular shape similar to the lower surface 5 of the diaphragm 1 and has a corrugated cross section that passes through the center and is perpendicular to the molding surface 101a.
This is a ceramic thin plate 11
A ceramic upper die 10 having a predetermined concentric circular shape similar to the upper surface 6 of the diaphragm and having a corrugated cross section passing through the center and perpendicular to the molding surface 102a.
Arrange the two in a stack. However, the molding die 10 in this example
1, 102 are made of alumina ceramic, and the molding surface 10
The pitch of the waveform in 1a and 102a is the diaphragm 1
However, the amplitude is about 50% larger than the set amplitude S of the diaphragm 1. In addition, the molding die surface 10 corresponding to the radius R of the diaphragm 1 forming the waveform.
The radius Ra of 1a and 102a is about 100% of the radius R.

Thus, the ceramic thin plate 11 arranged in this manner is maintained at a temperature range showing superplastic deformation in this example, about 1200 to 1300 ° C., and below that, a predetermined strain rate is set. For a period of time, the molding dies 101 and 102 are pressed up and down to cause the ceramic thin plate 11 to undergo superplastic deformation until a predetermined amplitude S is reached. Thus, the fired ceramic thin plate 11 is formed into a predetermined shape by superplastic deformation, and becomes the desired ceramic diaphragm 1.

Diaphragm 1 thus obtained
Can reduce the cost because it does not require a cutting or polishing step with poor processing efficiency. Moreover, since there is no polishing stock removal, the material yield is high. Further, in the case of cutting or polishing, it is difficult to use a thin plate having a wall thickness of 1 mm or less, but in the present manufacturing method by superplastic deformation, a thinner plate is easier to form. Further, since the ceramic thin plate 11 is formed after firing, there is no large shrinkage as in the case of processing at the same time as firing, and the dimensional accuracy is less likely to be reduced.

Further, the molds 101 and 102 are preferably made of the above-mentioned ceramics. Although iron is disposable, it has a large difference in thermal expansion coefficient from ceramics, but ceramics have high heat resistance and excellent durability, so they can be used many times, reducing the cost of molds. To be This is also because, unlike those made of iron, the coefficient of thermal expansion approximates that of the ceramic thin plate 11.

[0020]

EXAMPLE In the above manufacturing method, a raw material powder containing a predetermined additive and containing zirconia powder as a main component is formed into a sheet shape, which is fired to obtain a ceramic thin plate having a diameter of 60 mm and a wall thickness of 0.1 mm. 6) having a concentric circular molding surface having a corrugated cross-section.
Sandwiched between 102, 1300 to 1600 ℃, pressure 10
By applying pressure for 3 hours under the condition of kg / cm ² , a ceramic diaphragm having a substantially concentric circular shape in plan view and having a wavy curved section passing through its center and perpendicular to the surface was manufactured. The waveform of the formed diaphragm 1 has a pitch (P) of 11 mm, an amplitude (S) which is a drawing depth of 1.4 mm, and a radius R of a peak or a valley of the waveform in FIG.
Is 6 mm.

With respect to the diaphragm 1 thus manufactured, the peripheral edge 4 is fixedly mounted in the stainless steel case 51 shown in FIG. 8, and a predetermined differential pressure (P1-P
2) was added and the maximum deflection amount (deflection at the center of the diaphragm) at each differential pressure was measured by a non-contact laser displacement meter. The results are as shown in Table 1. Although not shown, the comparative example is a flat ceramic diaphragm having the same thickness.

[Table 1]

As is clear from Table 1, 20 kPa-
It can be seen that at 100 kPa, the diaphragm 1 of the present example has a maximum bending amount that is about twice as large as that of the comparative example, and is extremely excellent in pressure responsiveness.

Next, regarding the shape of the cross-sectional waveform, the pitch (P) is 11 mm and the amplitude (S) is 1.4 m, as in the previous example.
m, radius R is 6 mm, while wall thickness is 0.05 mm,
Ceramic diaphragms of 0.5 mm and 0.75 mm were made in the same manner as the previous example, and each was 100 k
The maximum amount of deflection when a pressure of Pa was applied was confirmed. The results are as shown in Table 2. In addition, the pressure when superplasticizing a ceramic thin plate (sintered body) has a wall thickness of 0.05 mm.
In case of 0.1 mm, 10 kgf / c
m ² and wall thickness of 0.5 mm, 70 kgf / c
m ² and 100 kg when the wall thickness is 0.75 mm
f / cm ² . The comparative example is a flat ceramic diaphragm. Incidentally, when the wall thickness was 1.0 mm, it could not be manufactured because it was destroyed during superplastic deformation.

[Table 2]

As is clear from this result, in each of the examples (thickness 0.1 to 0.75 mm), the maximum amount of deflection that is 2 to 25 times that of the comparative example is secured. As described above, the diaphragm of this example has a remarkable superiority in the pressure responsiveness as compared with the flat diaphragm. Further, when the wall thickness was 0.05 mm, the maximum deflection of 3.7 mm was obtained in the example, but in the comparative example, it was broken during the pressurization. This proves the good pressure response of the diaphragm of the present invention.

Further, the thickness of the ceramic diaphragm is 0.1 mm, the pitch is constant at 11 mm, and the amplitude S is 0.44 mm, 1.1 m from 1.4 mm mentioned above.
A sample having a smaller value of m was prepared, mounted in a stainless steel case 51, and the maximum deflection amount was compared with a differential pressure of 100 kPa. The results are as shown in Table 3.

[Table 3]

From this result, the maximum deflection has an amplitude of 0.44.
When mm (amplitude / pitch ratio is 0.04), the increase is 15% compared to the comparative example without amplitude, but when the amplitude is 1.1 (amplitude / pitch is 0.1) or more, there is no amplitude. It can be seen that the maximum bending is 80% or more as compared with the comparative example. From this, it can be seen that the larger the amplitude is, the better the pressure response is.

Further, for the thickness of 0.1 mm,
Create a diaphragm with different amplitude and pitch, 100
Deflection was confirmed when a pressure of kPa was applied. The results are as shown in Table 4.

[Table 4]

From this table, it can be seen that the larger the amplitude and the larger the pitch in the tested range, the easier the bending (the better the response). The thickness, amplitude, and pitch of the ceramic diaphragm according to the present invention may be appropriately set according to the application of the diaphragm and the like.

[0029]

As is apparent from the above description, according to the present invention, it is possible to provide a ceramic diaphragm having excellent corrosion resistance and high pressure responsiveness capable of ensuring a large amount of flexural deformation. Further, according to the above-mentioned manufacturing method, it is possible to obtain a ceramic diaphragm having a desired cross-sectional shape without requiring grinding or polishing which has poor processing efficiency. In addition, since a polishing stock removal is unnecessary, the material yield is high.

[Brief description of drawings]

FIG. 1 is a conceptual plan view showing an embodiment of a diaphragm according to the present invention.

FIG. 2 is a central longitudinal sectional view of FIG.

FIG. 3 is a partially enlarged view of FIG. 2;

FIG. 4 is a partially enlarged view showing another embodiment of the waveform of the diaphragm according to the present invention.

FIG. 5 is a partially enlarged view showing another embodiment of the waveform of the diaphragm according to the present invention.

FIG. 6 is a diagram illustrating a method of forming the diaphragm according to the present invention by superplastic deformation.

7 is a partially enlarged view of FIG.

FIG. 8 is a sectional view illustrating a state in which the diaphragm according to the present invention is attached to the device.

[Explanation of symbols]

 1 Ceramic Diaphragm 2 Center 3 Corrugated Part 4 Periphery 5,6 Ceramic Diaphragm Surface 11 Ceramic Thin Plate (Sintered Body) 101, 102 Mold before Superplastic Deformation 101, 102a Molding Surface S Amplitude P Pitch

Claims (3)

[Claims] 1. A ceramic diaphragm, which has a substantially concentric circular shape in plan view and is formed so that a cross section passing through the center thereof and perpendicular to the surface has a corrugated shape. 2. The ceramic diaphragm according to claim 1, which is a thin plate having a wall thickness of 0.75 mm or less. 3. A method for producing a ceramic diaphragm which has a substantially concentric circular shape in plan view and has a corrugated cross section passing through the center and perpendicular to the surface, and which has a calcined wall thickness of 0.75 mm or less. A circular ceramic thin plate is sandwiched between the molding surfaces of two molding dies each having substantially concentric molding surfaces substantially corresponding to both surfaces of the ceramic diaphragm, and the ceramic thin plate exhibits a superplastic phenomenon in a temperature range. A method for manufacturing a ceramic diaphragm, characterized in that the cross-section is formed into a corrugated shape by pressurizing with pressure and superplastic deformation.