JPH0571893B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a high-sensitivity pressure sensor, and more specifically, by using a zirconium oxide thin plate for the diaphragm of the detection part, the detection part can be made smaller and thinner. The present invention relates to a capacitive pressure sensor that enables high sensitivity and enables high sensitivity.

[Prior Art] Generally, what is called a pressure sensor is a LVDT (Linear Variable Differential).
Transformers), capacitive type and semiconductor diffusion type. These are used appropriately depending on the purpose, but capacitance pressure sensors are inexpensive, have a wide range of uses, and are being actively developed.

In addition, the advantages of capacitive pressure sensors include the following: High accuracy over a wide temperature range;
Can be used at high temperatures (-30 to 120℃).

Due to the structure of the detection capsule, it is resistant to contamination and will not break even if excessive pressure is applied.

Excellent durability.

However, since this capacitive sensor uses alumina as a diaphragm, it has low elastic deformability under pressure and poor sensitivity. In other words, it cannot follow minute pressure changes.

Due to the strength of alumina, if a thin plate of 0.3 mm or less is used, it will easily break. The detection part is required to be thin and small, but because alumina is used for the diaphragm, it is thick and large.

[Problems to be Solved by the Invention] In view of the above problems, an object of the present invention is to provide a highly sensitive, small and thin pressure sensor.

[Means for Solving the Problems] This object of the present invention is achieved by using a zirconium oxide thin plate for the diaphragm of the detection section of the pressure sensor.

The pressure sensor of the present invention is characterized in that at least the diaphragm of the detection section is made of a zirconium oxide thin plate.

The first cross-sectional view of the detection part of the pressure sensor of the present invention is
As shown in the figure. In FIG. 1, 1 is a ceramic diaphragm, 2 is a ceramic substrate, 3 is glass, and 4 is a ceramic diaphragm.
5 represents an electrode, and 5 represents a lead wire.

This detection section has a capsule structure, and a diaphragm 1 and a lower substrate 2 are pasted together in parallel to each other, and a vacuum is created between them and sealed with a glass 3. When pressure is applied to the diaphragm 1 of this detection part, the diaphragm 1 deforms elastically in proportion to the pressure, but the displacement at the center is larger than the displacement at the outside. Therefore, in diaphragm 1 inside the capsule,
The diaphragm electrode 4a and the lower substrate 2 are provided with an inner electrode 4b and an outer electrode 4c, respectively, and the capacitance (Cr) formed by the outer electrode 4c is
Compare this with the capacitance (Cp), which varies greatly depending on pressure, and extract it as a direct current proportional to pressure. Further, the diaphragm electrode 4a is connected to a diaphragm lead wire 5a, the inner electrode 4b is connected to an inner electrode lead wire 5b, and the outer electrode 4c is connected to an outer electrode lead wire 5c.

The thickness of the detection part can be reduced by using a zirconium oxide thin plate for the diaphragm, and it is also possible to manufacture capsules with a 10 mm square or round shape.

In the present invention, a zirconium oxide thin plate is used for the diaphragm 1. This zirconium oxide thin plate contains 2.0 yttrium oxide (Y ₂ O ₃ ).
It is desirable that the content be 6.0%, and if it is outside this range, elasticity tends to be poor.

A doctor blade method is used as a method for manufacturing such a zirconium oxide thin plate. This method uses, for example, zirconium oxide powder with an average crystal grain size of 1.2 μm or less in which yttrium oxide as a stabilizer with an average grain size of 1.0 μm or less, preferably 0.5 μm or less is uniformly dispersed, and sintering is performed using a doctor blade method. After molding so that the thickness of the subsequent molded product is 150 μm or less, and then drying as necessary,
It is sintered at 1300-1600℃ and used as a substrate. In manufacturing by such a doctor blade method, the average crystal grain size of zirconium oxide is adjusted, and in addition to yttrium oxide as a stabilizer, binders such as polyvinyl butyral and peptizers such as triolein are used. By appropriately selecting organic solvents such as , plasticizers, and methyl ethyl ketone and blending them in appropriate amounts, it is possible to obtain ultrathin plates that are free from fine defects and uneven thickness and have high elasticity.

By using the zirconium oxide thin plate thus obtained for the diaphragm and substrate, it becomes possible to manufacture a capacitive pressure sensor having an ultra-thin detection section with a thickness of 0.5 mm or less.

[Examples] Hereinafter, the present invention will be explained in more detail based on Examples.

Example 1 A highly accurate pattern is screen printed on a 1 inch square, 0.1 mm thick zirconium oxide thin plate, and a diaphragm electrode 4a with a thickness of several microns is made as shown in Figure 2a.
It was formed as a diaphragm. Also, 1
Figure 2b on an inch square, 0.4mm thick alumina substrate.
An inner electrode 4b and an outer electrode 4c having the following patterns were respectively formed by the same method. The electrode material is
It is a silver-palladium alloy (Ag-Pd). next,
Both substrates were pasted together in parallel with a gap of 12 μm±1 μm, and sealed with glass 3 while leaving the gap in vacuum. Each electrode is guided with a lead wire, a 1-inch square detection capsule is made, the pulse width of the comparator is determined, and the signal is passed through an integration circuit and an amplification circuit.
It was monitored as a voltage change.

The output characteristics of the resulting high-sensitivity pressure sensor are shown in Figure 3 in comparison with a conventional sensor of the same type using alumina for the diaphragm.

As is clear from the output voltage characteristics with respect to pressure shown in FIG. 3, the pressure sensor of the present invention exhibits a remarkable improvement in sensitivity on the low pressure side compared to a conventional pressure sensor using an alumina diaphragm.

[Effects of the Invention] As described above, the pressure sensor of the present invention having a detection portion made of a zirconium oxide thin plate as a diaphragm has the following effects.

Since a highly elastic thin plate of zirconium oxide is used as the detector diaphragm, the sensitivity of conventional sensors of the same type can be greatly improved.

Since a zirconium oxide thin plate with high elastic deformability is used as the diaphragm, not only can the detection section be made thinner, but the set area can also be made smaller.

The improved detection sensitivity increases the S/N ratio, improves reliability as a pressure sensor, and facilitates processing of attached circuits.

Zirconium oxide has high strength and toughness, so it is difficult to break even when thinned to 0.3 mm or less.
It also has a large elastic deformability. Furthermore, since the amount of elastic deformation such as bending increases as the thickness is reduced, zirconium oxide can be made thinner to significantly increase the amount of deformation in response to pressure, and the detection sensitivity of the sensor can be increased accordingly.

It has a simpler structure than the LVDT type, and does not require complex and sophisticated techniques such as diffusion processing and repeated etching compared to the semiconductor diffusion type. Therefore, the pressure sensor of the present invention is less expensive than these types and costs about the same as a conventional capacitive pressure sensor.

[Brief explanation of the drawing]

Fig. 1 is a structural diagram of the pressure detection capsule of the present invention, Fig. 2a is a diagram of the electrode shape of the diaphragm part,
FIG. 2b is a diagram showing the electrode shape of the substrate part, and FIG. 3 is a diagram showing the measurement results of the output characteristics of the pressure sensor. 1: Ceramic diaphragm, 2: Ceramic substrate, 3: Glass, 4a: Electrode for diaphragm,
4b: inner electrode, 4c: outer electrode, 5a: diaphragm lead wire, 5b: inner electrode lead wire,
5c: Lead wire for outer electrode.

Claims (1)

[Claims] 1. A pressure sensor, characterized in that at least the diaphragm of the detection section is made of a zirconium oxide thin plate. 2. The pressure sensor according to claim 1, wherein the lower substrate of the detection section is made of a zirconium oxide thin plate. 3. The pressure sensor according to claim 1 or 2, wherein the zirconium oxide thin plate is made of zirconium oxide containing 2.0 to 6.0 mol% of yttrium oxide. 4. The pressure sensor according to claim 1, 2, or 3, wherein the detecting portion has a thickness of 0.3 mm or less.