JP4828804B2 - Ceramic diaphragm, manufacturing method thereof, and pressure sensor - Google Patents

Description

  The present invention relates to a ceramic diaphragm, a manufacturing method thereof, and a pressure sensor, and more particularly to a ceramic diaphragm having a plate-like diaphragm body and an annular support portion for supporting the diaphragm body, a manufacturing method thereof, and a pressure sensor.

  A conventional pressure sensor includes a plate-like diaphragm main body and a ceramic diaphragm having an annular support portion that supports the diaphragm main body, a sensor element that is provided at the center of the outer surface of the diaphragm main body and outputs a signal based on deformation of the diaphragm main body. When a pressure medium is introduced into the ceramic diaphragm, pressure is detected and measured by a signal from a sensor element based on deformation of the diaphragm body.

  Conventionally, in order to secure the pressure resistance of the cap-shaped ceramic diaphragm, the inner surface of the connecting portion between the diaphragm main body and the annular support portion is formed smoothly by an arc surface or the like to suppress stress concentration in the connecting portion ( Patent Document 1).

As a conventional pressure sensor manufacturing method, it is generally known that a ceramic diaphragm is formed by dry pressing a ceramic powder. A desired shape is formed by this molding process, and organic components are removed by a subsequent firing process. Complete integration is achieved by sintering. Then, the outer surface side of the diaphragm main body was polished by a polishing process, and finished to a desired thickness dimension and flatness.
JP-A-5-5664

  However, in the conventional pressure sensor, when a pressure medium is introduced into the ceramic diaphragm, there is a problem that a large stress is generated in the connecting portion between the diaphragm main body and the annular support portion, and sufficient pressure resistance cannot be secured. .

  That is, in the conventional pressure sensor, a difference occurs in the density of the molded body between the diaphragm main body and the annular support portion during molding, and this causes a difference in shrinkage due to sintering in the firing process. Normally, in the same molded body, a thin part such as a diaphragm main body and a thick part such as an annular support part coexist, and the flow of the raw material powder in the dry press molding process or between the powder and mold Under the influence of friction, the density of the compact in the thin portion tends to increase. On the other hand, the shrinkage amount of the outer dimension due to firing tends to increase as the molded body density decreases. For this reason, the shape of the diaphragm main body that has undergone the firing process becomes a shape in which the central portion of the inner surface of the diaphragm main body 33 swells into a convex shape as shown in FIG. 6 as compared to the shape obtained in the molding process. That is, the center of the diaphragm main body 33 having a high density of the molded body is thick and has a thin shape in the vicinity of the connection portion with the annular support portion 34 having a low density of the molded body. Reference numeral 35 denotes a sensor element.

  In such a shape, when a pressure medium is introduced into the ceramic diaphragm, relatively large stress is generated due to stress concentration at the connecting part of the diaphragm main body that is thinner than the central part of the diaphragm main body and the annular support part. As a result, there was a problem that the pressure resistance was insufficient.

  An object of the present invention is to provide a ceramic diaphragm, a method for manufacturing the same, and a pressure sensor that reduce stress generated in a connecting portion between a diaphragm main body and an annular support portion and have excellent pressure resistance.

The present invention has a plate-like diaphragm main body and an annular support portion that supports the diaphragm main body, and is configured such that one main surface of the diaphragm main body and the inner side surface of the annular support portion are connected to each other. In the ceramic diaphragm, the diaphragm main body includes a concave portion provided in a central portion of the one main surface, and a step portion formed between the inner surface of the concave portion and the one main surface, and the diaphragm main body The ceramic main diaphragm is characterized in that the connecting portion between the one main surface and the inner side surface of the annular support portion and the stepped portion are formed so that the surface thereof is curved in a sectional view. .

A recessed amount a of the central portion in the recess of the diaphragm body, the ratio of the thickness t of the diaphragm body (a / t) is 0.02 to 0.20 Dearuko and are preferred.

Moreover, it is preferable that the surface roughness of a diaphragm main body is 0.2 micrometer-0.6 micrometer by arithmetic mean roughness (Ra) .

  The ceramic diaphragm of the present invention is characterized in that at least the diaphragm body is made of an alumina-zirconia ceramic.

A method for producing a ceramic diaphragm comprising a step of dry-pressing ceramic powder to produce a ceramic diaphragm molded body and a step of firing the ceramic diaphragm molded body, wherein the die for pressing used in the dry press Is a step portion formed between a convex portion provided at the center of the surface forming the one main surface side of the diaphragm main body and the surface forming the one main surface side of the convex portion. And a connecting portion between a surface forming the one main surface side and a side surface of the pressing mold, and the stepped portion are formed so that the surface thereof is curved in a sectional view . Also provided is a method for producing a ceramic diaphragm .

In addition , a pressure sensor using the ceramic diaphragm , wherein a sensor element is provided at the center of the other main surface of the diaphragm main body , is also provided.

Further, a pressure sensor using the ceramic diaphragm, a pressure sensor characterized by comprising providing a thick-film resistor on the other main surface of the said diaphragm body, together provide.

  In the ceramic diaphragm of the present invention, since the upper surface portion of the inner surface of the diaphragm main body is concave, the shape of the central portion of the diaphragm main body is thinner than the thickness in the vicinity of the connecting portion between the diaphragm main body and the annular support portion. Thus, the stress generated at the connecting portion between the diaphragm main body and the annular support portion can be reduced, and the pressure resistance can be improved.

  In addition, by making the central part of the inner surface concave, the stress generated at the connecting part between the diaphragm main body and the annular support part can be reduced more reliably, and both strength prevention due to the thinned central part of the diaphragm main body is achieved. can do.

  Further, the upper surface portion of the inner surface has a concave shape over the entire surface, and the ratio (b / t) of the amount b of the recess to the thickness t of the upper surface portion is 1.2 to 6.0, the upper surface of the inner surface In the case where the central part of the part has a concave shape, the ratio (a / t) of the concave amount a of the central part and the thickness t of the upper surface part is 0.02 to 0.20. It is possible to achieve both the reduction of the stress generated in the connecting portion with the support portion and the prevention of the strength reduction due to the thin central portion of the diaphragm main body, and the highest pressure resistance.

  Moreover, when the surface roughness of the diaphragm body is 0.2 to 0.6 μm in terms of arithmetic average roughness (Ra), when forming a pressure sensor, a sensor element or a thick film resistor formed on the outer surface thereof It can be provided without playing or bleeding.

  Further, the ceramic diaphragm of the present invention has a large bending strength because at least the diaphragm main body is made of alumina-zirconia-based ceramics. Therefore, when the pressure sensor is formed, the ceramic diaphragm has a large pressure resistance against the pressure acting on the diaphragm main body. Since it has strength, high accuracy can be maintained for a long time.

  Further, in such a manufacturing method of the ceramic diaphragm, since the center part of the surface forming the diaphragm main body is dry-pressed using a pressing mold having a convex shape, it matches the shape of the inner surface of the diaphragm main body molded body. By adopting a concave shape, this shape can be maintained even after sintering.

  In addition, the pressure sensor using the diaphragm of the present invention has a sensor element at the center of the outer surface of the diaphragm body or a thick film resistor on the outer surface, so that the upper surface of the inner surface is concave as described above. Suitable for pressure sensors used in high pressure range. In addition, when thick film resistors are used, thick film printing can cover a wide range from low pressure to high pressure without affecting the amount of distortion of the ceramic that forms the diaphragm body because the film thickness is thinner than the sensor element. The reliability of the pressure sensor can be improved.

  An embodiment of a ceramic diaphragm of the present invention will be described with reference to the drawings.

  As shown in FIG. 1A, the ceramic diaphragm of the present invention is a cap having a plate-like diaphragm main body 3 made of ceramics such as alumina and a cylindrical annular support portion 4 for supporting the diaphragm main body 3. The connecting portion 5 between the inner surfaces of the diaphragm main body 3 and the annular support portion 4 is smoothly formed in a curved shape such as an arcuate surface, and the stress concentration in the connecting portion 5 is suppressed.

  As will be described in detail later, this ceramic diaphragm is used as a pressure sensor as shown in FIGS. 4 and 5. As shown in FIG. 4, the ceramic diaphragm 1 is provided with a sensor element 2. As shown in FIG. 5, the thick film resistor 6 is printed on the ceramic diaphragm 1.

  Such a pressure sensor detects the deflection distortion of the diaphragm body 3 caused by the differential pressure between the pressure in the annular support 4 and the outside of the annular support 4 maintained at a specific pressure. It is detected by the body 6.

  Here, in the ceramic diaphragm 1 of the present invention, it is important that the upper surface portion 1a of the inner surface has a concave shape as shown in FIG.

  Thereby, since the upper surface portion of the outer surface of the ceramic diaphragm 1 is flat, the thickness of the central portion of the upper surface portion 1a of the inner surface is thinner than the thickness in the vicinity of the connecting portion 5 of the diaphragm main body 3 and the annular support portion 4. Thus, the stress generated in the connecting portion 5 between the diaphragm main body 3 and the annular support portion 4 can be reduced, and the pressure resistance can be improved.

  Further, the upper surface portion 1a of the inner surface has a stepped cross-sectional shape such that the center portion of the diaphragm main body 3 becomes a concave bottom surface, or a concave shape having a circular arc shape that is smooth toward the center of the diaphragm main body 3. As long as a part is concave, various shapes can be used. In particular, it is preferable to have a cross-sectional arc shape as shown in FIG. 1A, and stress can be applied more evenly. .

  Furthermore, when the upper surface portion 1a of the inner surface is concave over the entire surface, it is preferable that the ratio (b / t) between the amount of the recess b and the thickness t of the upper surface portion is 1.2 to 6.0.

  As shown in FIG. 1 (a), the amount of recess b is from the side surface of the inner surface of the annular support portion 4 and the boundary 7 that is the starting point of the connecting portion 5 to the most recessed point of the upper surface portion 1a of the inner surface. It shows the amount.

  Thereby, the stress which generate | occur | produces in the connection part 5 of the diaphragm main body 3 and the cyclic | annular support part 4 can further be reduced, and when applying a fixed pressure, for example, 3 MPa, to the diaphragm main body 3 from the cap shape inner side of the ceramic diaphragm 1, The strain amount is around 0.02, and can be stably put in the strain range required for the pressure sensor.

  When the ratio (b / t) is less than 1.2, the pressure resistance is weak or the strength variation is large, so that stable quality cannot be maintained. On the other hand, if it exceeds 6.0, the pressure resistance strength becomes strong, but the amount of distortion becomes extremely small, and the responsiveness when pressure is applied when used as a pressure sensor is deteriorated.

  Further, the amount of strain necessary for the pressure sensor is 0.004 mm to 0.045 mm, and the ratio b / t is more preferably 1.25 to 5.5.

  Furthermore, as for the ceramic diaphragm 1 of this invention, as shown in FIG.1 (b), it is preferable that the center part in the upper surface part 1a of an inner surface is concave shape.

  Thereby, the stress which generate | occur | produces in the connection part 5 of the diaphragm main body 3 and the cyclic | annular support part 4 can further be reduced, and a pressure resistance can be improved.

  Moreover, it is preferable that ratio (a / t) of the amount of recesses a in the central portion of the upper surface portion 1a of the inner surface and the thickness t of the upper surface portion is 0.02 to 0.20.

  Here, the recess amount “a” at the center of the upper surface portion 1 a of the inner surface of the diaphragm body 3 is the outer edge of the diaphragm body 3, that is, the connection between the diaphragm body 3 and the annular support portion 4, as shown in FIG. The thickness of the diaphragm body 3 is indicated on the basis of the plane formed by the boundary line of the portion 5, and the thickness t of the center portion of the diaphragm body 3 is the thickness of the diaphragm body 3 at the center portion of the recessed portion. It is.

  Thereby, it is possible to achieve both the reduction of the stress generated in the connecting portion 5 between the diaphragm main body 3 and the annular support portion 4 and the prevention of the strength reduction due to the thin central portion of the diaphragm main body 3, and the highest pressure resistance. At the same time, when a constant pressure, for example, 3 MPa, is applied to the diaphragm main body 3 as a water pressure from the inside of the cap shape of the ceramic diaphragm 1, the strain amount becomes around 0.02, and can be stably put in the strain range necessary for the pressure sensor. Furthermore, the ratio a / t is more preferably 0.05 to 0.15.

  When the ratio (a / t) is less than 0.02, the pressure resistance becomes weak, the strength variation becomes large, and stable quality cannot be maintained. On the other hand, if it exceeds 0.20, the pressure resistance becomes strong, but the amount of strain becomes extremely small, and the responsiveness when pressure is applied when used as a pressure sensor deteriorates.

  Further, the thickness t of the central portion of the diaphragm main body 3 is 0.10 to 3 mm, particularly 0.15 mm or more in order to ensure the strength of the diaphragm main body 3. Further, the thickness of the annular support portion 4 is set to 0.5 to 20.0 mm.

  In the ceramic diaphragm 1 of the present invention, at least the surface roughness of the diaphragm main body 3 is preferably 0.2 to 0.6 μm in terms of arithmetic average roughness (Ra).

  This is because when used as a pressure sensor, the amount of strain due to the pressure acting on the diaphragm main body 3 acts uniformly and stabilizes without any variation in pressure resistance.

  Furthermore, in order to obtain a stable surface condition in such a range of surface roughness, after grinding the wheel, be sure to use a dummy substrate to adjust the wheel surface and check the finished surface roughness. Then, it is preferable to process the ceramic diaphragm 1.

  The surface roughness of the diaphragm body 3 may be at least the outer surface within the above range, but the inner surface and the outer surface are preferably within the above range. Furthermore, it is preferable that the surface of the annular support portion 4, that is, the entire surface of the ceramic diaphragm 1 has an arithmetic average roughness (Ra) of 0.2 to 0.6 μm.

  In particular, in the case of a pressure sensor in which the thick film resistor 6 is printed on the ceramic diaphragm 1 as shown in FIG. 5, if the surface roughness of the upper surface of the outer surface of the diaphragm body 3 is too good, the printing of the thick film resistor 6 is performed. Occasionally bleeding or flipping occurs, and the printing state is poor and the product cannot be used. Further, when the pressure strength due to the surface roughness is seen, the strength tends to increase as the surface roughness improves. Therefore, the surface roughness of the diaphragm body 3 is 0.2 to 0.6 μm in terms of arithmetic average roughness (Ra), and further 0.3 to 0. 0 .mu.m from the relationship between the printability of the thick film resistor 6 and the pressure resistance. 5 μm is more preferable.

  Furthermore, in the ceramic diaphragm 1 of the present invention, it is preferable that at least the diaphragm body is made of an alumina-zirconia ceramic.

  Alumina-zirconia ceramics have a very high bending strength and a high pressure strength, and therefore can be used stably over a long period of time when used as a pressure sensor. In addition, since the strength can be kept high even if the diaphragm body 3 is made thin, the sensor sensing range using the ceramic diaphragm 1 can be expanded, and high quality can be ensured in terms of destruction safety.

  This alumina-zirconia ceramic has a composition ratio of 90 to 99.7% by weight of alumina and 0.3 to 10% by weight of zirconia. For example, an alumina powder having an average particle diameter of 1 to 6 μm, an average particle diameter It is preferable to use a raw material powder granulated with a spray dryer by adding a predetermined organic binder, lubricant, plasticizer and water to a zirconia powder of 0.1 μm to 1.6 μm.

(Production method)
Next, the manufacturing method of the ceramic diaphragm of this invention is demonstrated based on FIG. 2, 3 which is schematic sectional drawing.

  First, a ceramic diaphragm molded body is prepared using ceramic powder (including glass ceramic powder).

  When using alumina-zirconia ceramics as the ceramic powder, for example, zirconia 5 wt%, alumina 95 wt%, zirconia powder having an average particle diameter of 0.5 μm, and alumina powder having an average particle diameter of 1.5 μm are used. In addition, when using alumina ceramics, a predetermined organic binder, lubricant, plasticizer and water are added to alumina powder having a purity of 99.9% and an average particle size of 1.5 μm, and are granulated with a spray dryer. The raw material powder was used.

  The ceramic diaphragm molded body is produced using a press apparatus shown in FIG. The pressing device includes an upper punch 9 that forms a surface to which the sensor element 2 or the thick film resistor 6 is attached, an annular die 10 that forms an outer surface of the annular support 4, and an inner surface of the annular support 4. A floating lower punch 11 for floating and a fixed fixed lower punch 12 for forming the bottom surface of the annular support portion 4 are provided. A through hole is formed in the fixed lower punch 12, and the floating lower punch 11 is inserted into the through hole.

  The floating lower punch 11 and the stationary lower punch 12 are divided in order to uniformly compress the raw material powder, and may be an integrated type depending on the characteristics of the powder. Further, in order to perform more precise control, the die 12 or the punch 12 may be a movable type. Further, the punches 9, 11, 12 and the working part of the die 10 are driven by hydraulic pressure or the like.

  A diaphragm molded body is produced using this press apparatus. First, the punches 9, 11, 12 and the die 10 are moved to a positional relationship as shown in FIG. 2B, and the formed ceramic material powder 13 is filled in the formed space. Next, as shown in FIG. 2 (c), the upper punch 9 is lowered and the ceramic raw material powder 13 is compressed to form a diaphragm molded body 14.

  In the diaphragm molded body 14, the lower punch 11 is designed so as to reduce variations in the molded body density between the portion corresponding to the annular support portion 4 (annular support portion molded body) and the portion corresponding to the diaphragm body 3 (diaphragm body molded body) as much as possible. It is also desirable to lower it slightly. Finally, as shown in FIG. 2 (d), the upper punch 9 is raised and pulled up from the die 10, and the lower punches 11 and 12 are also raised to a position where the upper surface thereof coincides with the upper surface of the die 10. Take out.

  Usually, a large number of diaphragm molded bodies 14 are produced by repeating FIGS. 2 (a) to 2 (d). Finally, these compacts are fired under appropriate conditions in a firing furnace or the like to form a cap-shaped ceramic diaphragm 1.

  And in this invention, as shown to Fig.3 (a), (b), the upper end surface (surface of the floating lower punch 11 which forms the upper surface part 1a of the inner surface of the diaphragm main body 3) is convex shape as the floating lower punch 11 It is said that.

  The upper end surface of the floating lower punch 11 is convex upward so as to match the shape of the upper surface portion 1a of the inner surface of the diaphragm body 3, and the upper surface portion 1a of the inner surface as shown in FIG. In the case where the entire surface has a concave shape that is a smooth spherical surface, as shown in FIG. In addition, the boundary between the upper end surface and the side surface, that is, the portion corresponding to the connecting portion 5 of the ceramic diaphragm 1 has an R surface shape, and the distance b ″ between the broken lines, which is the distance from the boundary between the side surface and the R surface to the apex. After the firing, a recess amount b of the upper surface portion 1a of the inner surface of the diaphragm body 3 is formed.

  In addition, when the central portion of the upper surface as shown in FIG. 1B has a concave shape with a smooth spherical surface, the upper end surface of the floating lower punch 11 is similarly centered as shown in FIG. 3B. A spherical convex portion 15 is formed in the portion. Further, the distance a ″ between the broken lines, which is the distance from the upper end surface of the convex portion 15 to the flat surface, forms the concave amount a at the center portion of the inner surface of the diaphragm body 3 after firing.

  In the present invention, a press pressure is applied to the upper punch 9 by a hydraulic device, and a press pressure is further applied to the lower punch 12 by another hydraulic system. It is desirable that the press pressure applied to the lower punch 12 portion is higher than the press pressure applied to the lower punch 11 portion. The ratio P1 / P0 between the press pressure P1 applied to the lower punch 12 portion and the press pressure P0 applied to the lower punch 11 portion is particularly effective when it is 1.01 to 3.5. For this purpose, a pressure sensor is attached to each punch to manage the pressure received individually.

  Further, it is desirable to polish the upper surface portion 1a of the inner surface of the diaphragm 1 after sintering. Thereby, the fine unevenness | corrugation of the inner surface which is easy to raise | generate the local stress concentration which causes a strength fall can be removed, and pressure resistance can be improved. In order to maintain the concave shape even after sintering, the pressing pressure by the pressing mold for pressing the annular support molded body is set higher than the pressing pressure by the pressing mold for pressing the diaphragm body molded body. It is desirable to do. Thereby, the difference of the molded object density of a diaphragm main body and an annular support part can be made small, and, as a result, a desired concave shape can be obtained accurately.

  The ceramic diaphragm thus produced is suitably used as a pressure sensor as described above.

  The pressure sensor of the present invention will be described in detail with reference to FIGS.

  First, as shown in FIG. 4, the sensor element 2 is provided at the center of the outer surface of the diaphragm body 3, and the ceramic diaphragm 1 supports the plate-shaped diaphragm body 3 for detecting pressure and the diaphragm body 3. It is made into the cap shape which has the cylindrical cyclic | annular support part 4 to perform, and the sensor element 2 is arrange | positioned in the center part of the outer surface of the diaphragm main body 3, and is comprised.

  Such a pressure sensor detects the deflection distortion of the diaphragm main body 3 caused by the differential pressure between the pressure inside the annular support portion 4 and the outside of the annular support portion 4 maintained at a specific pressure by the sensor element 2.

  Further, as shown in FIG. 5, the pressure sensor is more preferably provided with a thick film resistor 6 on the outer surface of the diaphragm body 3. The thick film resistor 6 is made of ruthenium oxide or the like and is formed with a thickness of 10 to 50 μm by printing. Similar to the above, such a pressure sensor detects the deflection strain of the diaphragm main body 3 caused by the differential pressure between the pressure inside the annular support 4 and the outside of the annular support 4 maintained at a specific pressure. It is detected by a change in the resistance value of the body 6.

  Therefore, the pressure sensor including the sensor element 2 or the thick film resistor 6 has a concave shape on the upper surface 1a of the inner surface of the ceramic diaphragm 1 as described above, so that the pressure medium is introduced into the ceramic diaphragm 1. When pressure is introduced, stress is not concentrated on the connecting part 5 between the diaphragm main body 3 and the annular support part 4 which is thinner than the central part of the diaphragm main body 3, so that the pressure resistance is increased and used for a long period of time. can do.

  Further, as shown in FIG. 5, when the thick film resistor 6 is used, the film thickness is smaller than that of the sensor element 2 in the thick film printing, so that the low pressure without affecting the distortion amount of the ceramic forming the diaphragm body 3. The pressure sensor can cover a wide range from the high pressure range to the high pressure range, and the pressure resistance can be further improved.

  Next, examples of the present invention will be described.

  First, as an example of the present invention, a ceramic diaphragm as shown in FIGS. 1A and 1B was produced.

  First, as alumina ceramics, a raw material powder made by adding a predetermined organic binder, lubricant, plasticizer and water to alumina powder having a purity of 99.9% and an average particle diameter of 1.5 μm, and granulating with a spray dryer, As an alumina-zirconia ceramic, a predetermined organic binder, lubricant, and plasticizer are used for ceramic powder containing 95% by weight of alumina having an average particle diameter of 1.5 μm, 0.5 μm of zirconia, and 5% by weight of zirconia. And water were added, and the raw material powders granulated with a spray dryer were molded by the pressing devices shown in FIGS.

  First, in order to obtain a sample in which the upper surface portion 1a of the inner surface of the ceramic diaphragm 1 has a spherical concave shape as shown in FIG. 1A, the outer diameter of the fixed lower punch 12 is 23.5 mm, the inner diameter is 11.6 mm, the floating As shown in FIG. 3A, the upper end surface of the lower punch 11 is a mold having a protruding amount b ″ of 0.7 to 0.75 mm, the molding pressure by the upper punch 9 is 150 MPa, and the upper punch 9 The floating lower punch 11 was slightly lowered at the same time as the pressurization by a cap to produce a cap-shaped diaphragm molded body. Then, after firing at 1570 ° C. to obtain a sintered body having an outer diameter of 20.0 mm and an inner diameter of 10.2 mm, the upper surface of the diaphragm main body is polished and finished so that the thickness t becomes 0.28 to 0.3 mm. After producing a cap-shaped diaphragm sample, the sensor element 2 was attached to the center of the outer surface of the diaphragm body 3 to produce a pressure sensor.

  Further, as shown in FIG. 1B, in order to obtain a sample in which only the central portion of the upper surface portion 1a of the inner surface of the ceramic diaphragm 1 has a concave shape, the upper end surface of the floating lower punch 11 is formed in the same molding as described above. As shown in FIG. 3 (b), a die having a protrusion amount a ″ of 0.03 mm is polished and finished so that the thickness t of the upper surface of the diaphragm body is 0.28 mm, and a cap-shaped diaphragm sample is obtained. And a sensor element 2 was attached to the center of the outer surface of the diaphragm body 3 to produce a pressure sensor.

  Recesses b and a and thickness t on the inner surface of the ceramic diaphragm 1 of each sample were measured with a dial gauge, and ratios b / t and a / t with respect to thickness t were calculated.

  Further, as a comparative example, a pressure sensor was manufactured in the same manner as described above using a mold having protrusions b ″ and a ″ of 0.0 mm (flat) on the upper end surface 14 of the floating lower punch 11 as in the past. The central portion of the inner surface of the diaphragm body 3 after polishing has a convex shape, and the amount of protrusion measured was a 'was 0.030 mm as shown in FIG.

In addition, the connection part of each sample was made into the curved surface shape with a curvature radius R of 115 mm, each was produced with alumina ceramics and alumina-zirconia ceramics, and the surface roughness of the diaphragm main body was 0.4 μm in Ra.

  Then, a water pressure test was performed in which the water pressure was gradually applied to the inside of the manufactured pressure sensor to 6.5 MPa, and the pressure until the pressure sensor was damaged was measured.

The results are shown in Table 1.

  From Table 1, it was found that the pressure sensor samples (Nos. 1 to 14) using the ceramic diaphragm of the present invention were damaged when the water break pressure was 5.7 MPa or more and had high pressure resistance.

  In particular, it was found that samples (Nos. 8 to 14) having a concave shape only at the center of the upper surface portion of the inner surface had higher pressure resistance.

  Moreover, among the samples having the shape shown in FIG. 1A, the samples having the ratio b / t in the range of 1.2 to 6 (Nos. 2 to 5) have a high water break pressure of 10.6 to 11.2 MPa. Stable strength could be shown. Similarly, among the samples having the shape shown in FIG. 1 (b), the samples having the ratio a / t in the range of 0.02 to 0.2 (Nos. 9 to 12) have a breaking pressure of 10.8 to 11. It was found that the strength was 8 MPa and higher.

Moreover, when the sample (No. 1-6, No. 8-13) which consists of alumina zirconia ceramics in each shape, and the sample (No. 7, 14) which consist of alumina are each compared,
The result showed a strength of 1.7 times or more.

(A), (b) is a schematic sectional drawing which shows an example of the ceramic diaphragm of this invention. (A)-(d) is process drawing for demonstrating the manufacturing method of the ceramic diaphragm of this invention. (A), (b) is explanatory drawing which shows the state which the top surface center part of the lower punch protrudes. It is a schematic sectional drawing which shows an example of the pressure sensor of this invention. It is a schematic sectional drawing which shows an example of the pressure sensor of this invention. It is a schematic sectional drawing for demonstrating the conventional pressure sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ceramic diaphragm 1a ... Upper surface part 2 of inner surface of ceramic diaphragm 2 ... Pressure sensor 3 ... Diaphragm main body 4 ... Annular support part 5 ... Connection part 6 of a diaphragm main body and an annular support part ··· Thick film resistor 7 ··· Border 8 between connecting portion and side ··· Opening portion 9 ··· Upper punch 10 ··· Die 11 · · · Floating lower punch 12 · · · Fixed lower punch 13 ··· -Ceramic raw material powder 14 ... Diaphragm compact 15 ... Convex part

Claims (7)

A ceramic diaphragm having a plate-like diaphragm main body and an annular support portion for supporting the diaphragm main body, wherein one main surface of the diaphragm main body and an inner side surface of the annular support portion are connected to each other. ,
The diaphragm main body includes a concave portion provided in a central portion of the one main surface, and a step portion formed between the inner surface of the concave portion and the one main surface,
The ceramic diaphragm characterized in that the connecting portion between the one main surface of the diaphragm main body and the inner side surface of the annular support portion and the stepped portion are formed so that the surface thereof is curved in a sectional view. .   2. The ceramic according to claim 1, wherein a ratio (a / t) of a recess amount “a” in the center portion of the diaphragm body to a thickness t of the diaphragm body is 0.02 to 0.20. Diaphragm.   3. The ceramic diaphragm according to claim 1, wherein at least a surface roughness of the diaphragm body is an arithmetic average roughness (Ra) of 0.2 μm to 0.6 μm.   The ceramic diaphragm according to any one of claims 1 to 3, wherein at least the diaphragm body is made of an alumina-zirconia ceramic. A process for producing a ceramic diaphragm comprising a step of dry-pressing ceramic powder to produce a ceramic diaphragm molded body, and a step of firing the ceramic diaphragm molded body,
The pressing mold used for the dry press has a convex portion provided at the center of the surface forming the one main surface side of the diaphragm body, and a surface forming the surface of the convex portion and the one main surface side. And a step portion formed between and
The connecting portion between the surface forming the one main surface side and the side surface of the pressing mold, and the stepped portion are formed so that the surface thereof is curved in a sectional view. Manufacturing method of ceramic diaphragm. A pressure sensor using the ceramic diaphragm according to any one of claims 1 to 4 , wherein a sensor element is provided at a central portion of the other main surface of the diaphragm main body. A pressure sensor using the ceramic diaphragm according to any one of claims 1 to 4 , wherein a thick film resistor is provided on the other main surface of the diaphragm main body.

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