JPH05333045A - Piezoelectric acceleration sensor - Google Patents

Abstract

PURPOSE:To easily miniaturize the apparatus and to measure even a small acceleration with high sensitivity by using a piezoelectric body showing a large amount of piezoelectric distortion which is formed of a porous piezoelectric material with many voids. CONSTITUTION:Powders of lead zirconate titanate(PZT) of about 1.2mum average particle size and metacrylic resin of about 30mum average particle size are blended in a suitable ratio, molded and baked. An electric field of approximately 1kV is applied to the baked body, which is then polarized. As a result, a piezoelectric body 1 is obtained. The mixing ratio of the PZT powders and resin powders determines the ratio of voids to the total volume of the obtained porous piezoelectric material (void volume), and also the amount of the piezoelectric distortion. Accordingly, since the piezoelectric body 1 is constructed as above, the amount of the piezoelectric distortion is made large, enabling detection of a small acceleration. Moreover, a minute difference of the acceleration can be detected with high sensitivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric acceleration sensor using a piezoelectric body.

[0002]

2. Description of the Related Art FIG. 1 is a sectional view showing the outline of the configuration of a piezoelectric acceleration sensor using a piezoelectric body. In the figure, 1 is a piezoelectric body, 2 is an electrode, 3 is a weight (inertial object), and 4 is Case 5, 5 is a base, 6 is a lead wire, and the arrow in the drawing indicates the polarization direction of the piezoelectric body 1.

This acceleration sensor is installed on an object to be measured for acceleration and measures the acceleration by the inertial force of the weight 3. That is, the acceleration received by the base 5 acts on the piezoelectric body 1 as an inertial force of the weight 3, and in response to this, the piezoelectric effect of the piezoelectric body 1 is exerted.
Is charged. The amount of electric charge charged in the piezoelectric body 1 is proportional to the strain of the piezoelectric body when a voltage is applied to the piezoelectric body 1, the mass of the weight 3, and the acceleration. At this time, the electrode 2
The voltage generated at both ends of is proportional to the charge generated in the piezoelectric body 1 and inversely proportional to the capacitance of the piezoelectric body 1. Therefore, this type of acceleration sensor detects the acceleration received at this voltage value.

The detection sensitivity of the device is determined by the performance of the piezoelectric body 1. That is, as the amount of electrification generated when the inertial force from the weight 3 is applied to the piezoelectric body 1, the greater the amount of piezoelectric strain and the smaller the capacitance of the piezoelectric body 1, the higher the sensitivity. (High resolution) device can be obtained, and the device can be easily downsized.

[0005]

As described above, since the performance of this type of piezoelectric acceleration sensor is determined by the amount of piezoelectric strain of the piezoelectric body, a piezoelectric body having a large amount of piezoelectric strain should be used for a high performance device. Must be used.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a highly sensitive piezoelectric acceleration sensor capable of detecting a large voltage even when the applied acceleration is small.

[0007]

A piezoelectric acceleration sensor according to the present invention is constructed by using a piezoelectric body having a large piezoelectric strain formed by using a porous piezoelectric material having a large number of holes. Characterize.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The configuration of the device according to the present invention is the same as the configuration shown in FIG. 1 described as a conventional technique except that the piezoelectric body 1 is different, and the duplicate description is omitted here.

Next, the piezoelectric body 1 of the present invention will be described. The piezoelectric body 1 according to the present invention is formed by using a porous piezoelectric material having a large number of holes. Then, the manufacturing method is as follows. Powder of a piezoelectric material such as lead zirconate titanate (PZT) and powder of an organic material such as methacrylic resin are mixed at an appropriate ratio, molded, fired, and polarized by applying an electric field. And manufacture.

This will be described in detail below. For example, a lead zirconate titanate (PZT) powder having an average particle diameter of 1.2 μm and a methacrylic resin powder (for example, a polymer of polymethylmethacrylate) having an average particle diameter of 30 μm are mixed at an appropriate ratio. This mixing ratio determines the ratio of pores to the total volume of the manufactured porous piezoelectric material (hereinafter referred to as porosity), and the amount of piezoelectric strain. Then, the piezoelectric body 1 of the present invention is obtained by molding and firing, applying an electric field of about 1 kV / mm and polarization.

FIG. 2 is a diagram showing the relationship between the porosity and the piezoelectric strain amount. As shown in the figure, the piezoelectric strain amount is always increased by making it porous, and the piezoelectric strain amount is the porosity. It turns out that it depends on. FIG. 3 is a diagram showing the relationship between the porosity and the relative permittivity. As the porosity increases, the relative permittivity, that is, the capacitance decreases, and the capacitance depends on the porosity. You can see what you are doing.

By constructing a piezoelectric acceleration sensor as shown in FIG. 1 with the piezoelectric body 1 thus obtained, the amount of piezoelectric strain of the piezoelectric body 1 can be increased, and a small acceleration which cannot be detected by the conventional device can be detected. In addition, a highly sensitive device capable of detecting a minute difference in acceleration can be obtained.

In the above embodiment, lead zirconate titanate is used as the piezoelectric material of the piezoelectric body 1 and methacryl resin powder is used as the organic material for forming the porosity. , Barium titanate or the like can be used, and other organic materials may be used as the material for forming the porosity.

[0014]

As described above, according to the present invention, a highly sensitive piezoelectric acceleration sensor can be obtained by constructing an apparatus using a piezoelectric body formed by using a porous piezoelectric material having a large number of holes. There is an effect that is.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a piezoelectric acceleration sensor.

FIG. 2 is a diagram showing a relationship between a porosity and a piezoelectric effect.

FIG. 3 is a diagram showing the relationship between porosity and relative permittivity.

[Explanation of symbols] 1 piezoelectric body 2 electrode 3 weight 4 case 5 base 6 lead wire

Claims (1)

[Claims] 1. An inertial object is mounted on a base, which is installed on an object to be measured whose acceleration is to be measured, through a piezoelectric body having extraction electrodes provided at both ends thereof, and the inertial force from the inertial object is generated by the received acceleration. In a piezoelectric acceleration sensor that measures the acceleration by detecting the amount of charge that is charged in the piezoelectric body due to the force acting on the piezoelectric body due to the piezoelectric effect, the piezoelectric body used in the device may be, for example, lead zirconate titanate. A piezoelectric acceleration sensor characterized by using a piezoelectric body made of a porous piezoelectric material in which a large number of holes are formed by using a piezoelectric material such as lead titanate or barium titanate.