JPS61266931A - Pressure sensor - Google Patents

Abstract

PURPOSE:To reduce a thermal stress in accordance with a variation of the ambient temperature and to improve a temperature characteristic and accuracy of pressure detection by making a diaphragm receiving the pressure of a ceramic. CONSTITUTION:The ceramic diaphragm 5 is formed by using the ceramic such as alumina and a piezoelectric substance 6 having electrodes 6a and 6b is fitted in a body on the pressure receiving face 51 and the opposite face 52 to form a pressure sensor. Hereby, since the temperature coefficients of the piezoelectric substance 6 and the diaphragm 5 are approximate, the thermal stress is reduced and the temperature characteristic is improved. Further, the ceramic diaphragm is excellent in an elastic characteristic, formability, fatigue, creep and corrosion resistance and furthermore, can be made large in compliance and highly sensitive. Further, an adhesive is not necessary to fit the piezoelectric substance 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a pressure sensor that uses a piezoelectric material as a pressure-to-electrical conversion element that converts pressure applied to a diaphragm into an electrical signal. , which has excellent elastic properties and formability, has a small temperature coefficient and is extremely stable against temperature fluctuations, and also has excellent fatigue resistance, creep resistance, and corrosion resistance, making it possible to obtain a pressure sensor with large compliance and high sensitivity. It is.

2. Description of the Related Art In this type of pressure sensor, a piezoelectric vibrator is attached to the surface of a pressure receiving plate, and the elastic deformation of the pressure receiving plate is converted into an electric signal by the piezoelectric vibrator and detected. FIG. 4 is a front cross-sectional view of a conventional example of this type of pressure sensor, in which a piezoelectric body 2 is bonded onto a surface 102 of a diaphragm 1 formed into a disc shape of a metal plate, on the opposite side from the pressure receiving surface 101. material 3
2a and 2b are electrodes of the piezoelectric body 2, and 4 is a peripheral support member.

Problems to be Solved by the Invention However, since the conventional pressure sensor uses a metal plate as the diaphragm 1, it has the following problems.

(L) The diaphragm l made of a metal plate has a large temperature coefficient and is easily affected by changes in ambient temperature.

(b) Since the diaphragm 1 is made of a metal material, and the piezoelectric body 2 is made of a ceramic material, the temperature coefficients between the two are different, causing thermal stress due to ambient temperature fluctuations, resulting in detection errors. There are problems such as generation of , and the temperature characteristics are not good.

(C) Since the structure is such that the diaphragm 1 and the piezoelectric body 2 having different temperature coefficients are bonded together using the adhesive 3 having a different temperature coefficient, the temperature characteristics are further deteriorated.

(d) Since the adhesive 3 is required, stress at the bonding surface increases when pressure is applied, which also reduces detection accuracy.

Means for Solving the Problems In order to solve the above-mentioned conventional problems, the present invention provides a pressure receiving section that integrates a diaphragm that receives pressure and a piezoelectric body that converts the pressure applied to the diaphragm into an electrical signal. In the pressure sensor, the diaphragm is made of ceramic.

The temperature coefficient of a ceramic diaphragm is significantly smaller than that of a metal diaphragm, and is close to that of a ceramic piezoelectric material, so the thermal stress associated with ambient temperature fluctuations is small, resulting in good temperature characteristics. become. Moreover, the ceramic diaphragm has elastic properties,
It has excellent formability, fatigue resistance, creep resistance, and corrosion resistance, as well as high compliance and high sensitivity.

In addition, the ceramic diaphragm can be integrated with the piezoelectric body made of ceramic by co-firing, which eliminates the need for an adhesive to fix the two, and reduces the temperature characteristics caused by the adhesive. It is possible to eliminate the deterioration of the bonding properties and the generation of stress at the joint surfaces when pressure is applied.

Example FIG. 1 is a front sectional view of a pressure sensor according to the present invention.

In this embodiment, a disk-shaped ceramic diaphragm 5 is formed using a ceramic material such as alumina, and a piezoelectric body 6 is integrally formed on a surface 52 of the ceramic diaphragm 5 on the opposite side from the pressure receiving surface 51.

6a and 6b are electrodes of the piezoelectric body 6.

The technology to obtain a thin plate with excellent elastic properties and mechanical strength using ceramic such as alumina has already been established, and this technology has made it possible to sufficiently reduce the thickness required for the ceramic diaphragm 5 of a pressure sensor. It is possible.

Simultaneous firing is the most preferable means for integrally bonding the piezoelectric body 6 to the ceramic diaphragm 5.As shown in FIG. 2, as shown in FIG. A possible method is to integrate the diaphragm 5 and the piezoelectric body 6 via the electrode material 6a and then sinter them. In addition, when the support member attached to the peripheral part of the ceramic diaphragm 5 is also formed of ceramic, as shown in FIG.
The ceramic diaphragm 5, piezoelectric body 6, and support member 7 are integrated, and then main firing is performed.

When the ceramic diaphragm 5 and the piezoelectric body 6 are integrated by co-firing, there is no need for an adhesive to join them together, which causes problems such as generation of thermal stress due to the adhesive and deterioration of temperature characteristics due to this. There is no possibility of problems such as detection errors caused by stress on the joint surface when pressure is applied.

Effects of the Invention As described above, the present invention provides a pressure sensor in which a piezoelectric body is provided on the surface of a diaphragm, in which the diaphragm is made of ceramic. It is possible to provide a pressure sensor that has a small temperature coefficient, is extremely stable against temperature fluctuations, has excellent fatigue resistance, creep resistance, and corrosion resistance, and has high compliance and high sensitivity.

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of a pressure sensor according to the present invention, FIG. 2 is a diagram showing a method for manufacturing a pressure sensor according to the present invention, FIG. 3 is a diagram showing another manufacturing method, and FIG. 4 is a diagram showing a conventional method. FIG. 3 is a front sectional view of the pressure sensor of FIG. 5... Ceramic diaphragm 6, φ, piezoelectric body

Claims (2)

[Claims] (1) A pressure sensor having a pressure receiving part that integrates a diaphragm that receives pressure and a piezoelectric body that converts the pressure applied to the diaphragm into an electrical signal, wherein the diaphragm is made of ceramic. (2) The pressure sensor according to claim 1, wherein the diaphragm and the piezoelectric body are integrated by simultaneous firing.