JPH0666482B2 - Mechanical-electrical conversion element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention uses a flexible piezoelectric material to convert mechanical stress into an electrical signal, or to convert an electrical signal into a mechanical vibration. Regarding the conversion element.

<Prior Art> A flexible piezoelectric material applied to this type of electromechanical conversion element is made by mixing ferroelectric ceramic particles such as lead zirconate titanate and lead titanate in synthetic rubber or synthetic resin. Due to its flexibility, it can be easily displaced with respect to mechanical stress and a good output voltage can be obtained. Therefore, ultrasonic transducers, hydrophones, vibration detection sensors for internal combustion engines, electric piano string vibration pickups, etc. It is used for various purposes.

As the electromechanical conversion element, two flexible electrodes are provided in pairs through a piezoelectric layer made of a flexible piezoelectric material, and the piezoelectric layers are polarized in the corresponding directions of the two electrodes, and at least one of them is disposed. The electrode is connected to a lead wire, and a signal voltage corresponding to mechanical stress is taken out from the lead wire.

However, in this type of conventional structure, when a load is applied at the connecting portion of the lead wire by pulling, bending, or swinging of the lead wire, this acts as a mechanical stress on the piezoelectric layer, which causes noise. Occurred, which was a cause of false detection.

It is an object of the present invention to provide a mechanical-electrical conversion element capable of preventing generation of a voltage due to a load at a connecting portion of the lead wire and extracting a good signal voltage.

<Means for Solving the Problems> In the present invention, two flexible electrodes are provided opposite to each other through a piezoelectric layer made of a flexible piezoelectric material, and the piezoelectric layers are polarized in the corresponding directions of the two electrodes. Further, in the electromechanical conversion element in which the electrode is connected to the lead wire, the piezoelectric layer in the partial region on the side connected to the lead wire is non-polarized.

Here, examples of the flexible piezoelectric material include piezoelectric rubber and piezoelectric resin. Further, the material applied to the electrode layer includes conductive rubber and the like.

<Operation> In the present invention, since the piezoelectric layer in the partial region on the side connected to the lead wire is made non-polarized, even if a load is caused by pulling the lead wire or the like at the connection portion, the load does not generate an electric signal. Not converted Therefore, it is possible to prevent the signal voltage from being disturbed by the load.

<Example> FIG. 1 shows a mechanical-electrical conversion element 1 in the form of a coaxial cable.
The present invention is applied.

Here, 2 is a piezoelectric layer made of piezoelectric rubber, and a core electrode layer 4 made of a conductive rubber having a core electrode 3 made of a linear conductive material is embedded in the center thereof. An electrode layer 5 made of conductive rubber is formed on the outer periphery of the electrode layer 5. The electrode layer 5 also covers the end portion of the piezoelectric layer 1, and a moisture-proof coating or the like is applied to the periphery of the electrode layer 5 if necessary.

6 is a lead wire, and the conductor wire 7 is inserted through the center of the lead wire,
Further, the outer peripheral surface is covered with the conductive braid 9 via the insulating layer 8 to form a known structure.

The core electrode 3 is exposed from the end of the electromechanical conversion element 1 and connected to the conductor wire 7, and a conductive tube 10 is externally fitted between the electromechanical conversion element 1 and the lead wire 6. The conductive tube 10 electrically connects the electrode layer 5 and the conductive braid 9.

In the above structure, the piezoelectric layer 2 has a partial region on the side connected to the lead wire 6 which is non-polarized and the other partial regions which are polarized in the radial direction.

In order to make the connection side partial region non-polarized, as shown in FIG. 1, the piezoelectric layer 2 is arranged with the polarized piezoelectric partial layer 2a on one end side and the non-polarized piezoelectric partial layer 2b on the connection side. It should be arranged.

As another means, a method may be used in which the entire piezoelectric layer 2 is radially polarized and then the connection side partial region of the piezoelectric layer 2 is heated to erase the polarization treatment.

FIG. 2 shows a plate-shaped electromechanical conversion element 20 to which the present invention is applied, in which electrode layers 22 and 22 made of conductive rubber are formed on the upper and lower surfaces of a piezoelectric rubber plate 21 (piezoelectric layer). ing. Conductive braids 23, 23 for connection are embedded in the electrode layers 22, 22, respectively. At the ends of the piezoelectric rubber plate 21, the conductive braids 23 and 23 are exposed and the lead wires 24 and 24 are connected.

Even with such a configuration, the piezoelectric rubber plate 21 has a polarized piezoelectric partial layer 21a arranged on one end side and a non-polarized piezoelectric partial layer 21b arranged on the connection part side. A non-polarizing process is applied to the area.

In the above-described embodiment, the lead wire 24 may be formed by cutting off the electrode layer 22 to expose the conductive braid 23 and connecting to the exposed braid 23 by means such as soldering.

<Advantages of the Invention> As described above, according to the present invention, the electrode layer is polarized except for the partial region on the side where the lead wire is connected. Therefore, a load is applied to the connection portion by pulling the lead wire or the like. Even if it happens,
This is not converted into a voltage, so that there is an excellent effect that a good output signal can be obtained.

[Brief description of drawings]

The attached drawings show an embodiment of the present invention. FIG. 1 is a vertical sectional side view of an embodiment in which the present invention is applied to a coaxial electromechanical conversion element 1, and FIG. It is a vertical side view of the applied example. 1; electromechanical conversion element, 2; piezoelectric layer, 3; core electrode, 4;
Core electrode layer, 5; Electrode layer, 6; Lead wire, 20; Mechanical-electrical conversion element, 21; Piezoelectric rubber plate, 22; Electrode layer, 23; Conductive braid, 24; Lead wire

Claims (3)

[Claims] 1. A piezoelectric layer made of a flexible piezoelectric material is interposed,
In a mechanical-electrical conversion element formed by pairing two flexible electrodes, polarizing the piezoelectric layer in the corresponding directions of the two electrodes, and further connecting the electrodes to a lead wire, A mechanical-electrical conversion element characterized in that a piezoelectric layer in a partial region is non-polarized. 2. A coaxial electromechanical conversion element comprising a core electrode embedded in the center of a piezoelectric layer, the outer surface of the piezoelectric layer being covered with a jacket electrode, and the electrode being connected to a lead wire. The electromechanical conversion element according to claim 1), wherein the piezoelectric layer in the partial region on the side connected to the lead wire is non-polarized. 3. Electrodes are formed on the upper and lower surfaces of the piezoelectric plate layer, respectively.
The mechanical layer according to claim 1), characterized in that the piezoelectric layer in the partial region of the electromechanical conversion element formed by connecting the electrode to the lead wire is connected to the lead wire is non-polarized. Electric conversion element.