JPS62153765A - Laminated type piezoelectric ceramic element - Google Patents

Abstract

PURPOSE:To make it possible to simply apply polarizing processing to a piezoelectric ceramic element by a pair of polarizable electrodes, by constituting the piezoelectric ceramic element by alternately laminating a piezoelectric ceramic layer and a layer of an insulating material having no or weak piezoelectric property. CONSTITUTION:Hollow cylindrical piezoelectric ceramic layers 11 having different diameters and insulating layers 15 having different diameters are laminated in a concentric circular state to constitute a laminated type piezoelectric ceramic element. Each inner electrode 12 for electric output is present on the surface of each piezoelectric ceramic layer 11 contacted with the insulating layer 15 and each inner electrode 12 is connected using a pair of outer electrodes 13 so as to make the piezoelectric ceramic layers 11 parallel. The inner electrodes 12 are connected to the outer electrodes 13 every other one by insulating protective films 14 and lead wires 5 for guiding electric output to the outside are connected to the outer electrodes 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a laminated piezoelectric ceramic element suitable for use in a torsional type acceleration sensor and the like.

[Conventional technology]

An example of a conventional acceleration sensor is shown in Fig. 7.

Figure A is a partially cutaway top view, and Figure B is -fH(j.

It is a cross-sectional front view. In these figures, 'ζ, (1) is a piezoelectric ceramic element, (2) is a weight, t3+ is a support, and +11 to (3) are attached concentrically. The electrodes are located on the inner and outer sides of the piezoelectric ceramic element (11), and polarization is performed by applying an electric field in the direction of the element surface (Z). When acceleration in the Z direction is applied, the shear stress increases with the weight (2
) acts on the element (11), and since the element (11 causes in-plane displacement distortion, an electric current 1-I is generated on the surface where the electrode is located,
The charge is passed through the connector (111f51) from the electrode (
4) and taken out as an electrical signal to the outside.

The weight (2) and the element (11), the element (11 and the support body (3)) are
It is fixed by continuous adhesive.

FIG. 8 shows an example of a piezoelectric ceramic element used in the sliding type acceleration sensor shown in FIG. 7. Same figure A
As shown in Neo in Figure B, the output electrodes (9) are formed on the inner and outer sides of the hollow cylindrical element (1) as described above, and as shown in Neo in Figure B, the polarization electrodes are placed on the top and bottom surfaces of the element (1). Polarization is performed by applying an electric field in the P direction. The piezoelectric ceramic element described above has low sensitivity and small capacitance because it is 1 ikj, and is therefore easily affected by electrical noise and the like. In addition, because adhesive is basically used to fix the element (11) and the weight (2), the adhesive part is particularly weak due to the structure, so the weight of the weight (2) is increased in order to improve sensitivity. This not only causes a decrease in the resonant frequency, but also causes a decrease in the strength of the bonded portion, resulting in disadvantages such as a decrease in acceleration resistance and an increase in the size and mass of the acceleration sensor.

In contrast to the above-mentioned methods, the method of improving sensitivity using a laminated piezoelectric ceramic element does not have the above-mentioned drawbacks. Figures 4 and 5 show an example of a laminated piezoelectric ceramic element used in a new type acceleration sensor. This laminated piezoelectric ceramic element is made of piezoelectric ceramics (1
1) is stacked in multiple layers, and by connecting output electrodes (12) in parallel to each layer, the sensitivity increases in proportion to the number of layers stacked compared to a single layer. The element shown in FIG. 4 is made by laminating hollow cylindrical piezoelectric ceramics concentrically, and FIG. 4A is a top view, and FIG. 4B is a partially cutaway perspective view. The polarization process is performed in a direction perpendicular to the top and bottom surfaces of the element, as indicated by the arrows in FIG. B, and the polarization direction is opposite in adjacent layers.

An internal electrode (12) for obtaining the electrical output of each piezoelectric ceramic (11) is provided on the joint surface between each piezoelectric ceramic (11). At the stacked end face where the internal electrode (12) is exposed, the internal electrode (12) is covered with insulation protection III (14).
After coating every other electrode (2), a conductive material such as silver paste is applied thereon to connect every other internal electrode (12) to form a pair of external electrodes (13). A pair of external electrodes (13) are connected to internal electrodes of mutually different polarities so as to obtain an electrical output proportional to the number of laminated layers.

The element shown in FIG. 5 is made by stacking a plurality of piezoelectric ceramics having the same ring shape in the height direction, and FIG. 5A is a top view, and FIG. 5B is a partially cutaway perspective view. The internal electrodes (12) are located on the joint surfaces between the piezoelectric ceramics (11), and the method of connecting the internal electrodes is the same as that shown in FIG. In this way, the laminated piezoelectric ceramic element used in the shear type acceleration sensor has the polarization axis direction and the electric axis direction the same, and has an angle of 9°.
Since they are orthogonal to each other and are less affected by the pyroelectric output, it is possible to obtain an acceleration sensor with low electrical noise caused by changes in ambient temperature and commercial sensitivity. It is necessary to provide

[Problem that the invention seeks to solve]

In the case of a single-layer piezoelectric ceramic element, for example, an output electrode (9) may be provided as shown in FIG. 8A, and a polarization electrode αω may be provided on a plane perpendicular to this as shown in FIG. 8B, and polarization treatment may be performed at °C. . However, in the case of laminated piezoelectric ceramic elements,
For example, as shown in Figure 5B, it is necessary to reverse the direction of polarization for every other layer, so as shown in Figure 6, polarization electrodes (101) must be attached to each layer for each layer. In the figure, Pl and P2 indicate opposite polarization directions.

Furthermore, since the voltages applied to adjacent layers are reversed, the polarization voltage applied to the piezoelectric ceramic layer affects the adjacent piezoelectric ceramic layer. In particular, since the thickness of a single layer of piezoelectric ceramic in a multilayer piezoelectric ceramic element manufactured by the Green Sea I method is as thin as 0.5 m or less, it is difficult to uniformly apply polarizing electrodes to each scrap. be.

In addition, polarization treatment before stacking piezoelectric ceramics is important because, in the case of lamination by adhesive, the piezoelectric ceramics do not harden at a temperature below one Curie point and lose their polarization, and the thickness of one layer cannot be made too thin. subject to restrictions. In particular, in the case of lamination by the green sheet method or the like, since a hot press is used as the lamination method, polarization disappears due to exposure to high temperatures, so it has not been possible to utilize the shear effect.

(Means for Solving the Problems) The present invention provides a layer of insulating material (hereinafter referred to as "insulation") with no or weak electrical conductor 11 on the 1- and 1-layers of pressure-sensitive ceramics.
The above-mentioned problems were solved by stacking the above-mentioned piezoelectric ceramic elements into a multilayer Ivi type piezoelectric ceramic element.

[Effect]

If the configuration described in 2 is adopted, the bow part will be to simply polarize the crushed ceramic element with a pair of polarizable electrodes.

[Actual hfti example]

FIG. 1 is a partially sectional perspective view showing a first embodiment of the present invention. This example is a laminated piezoelectric ceramic element in which hollow cylindrical piezoelectric ceramic layers and insulating layers having different diameters are stacked concentrically. Internal salt for electrical output & (12) is piezoelectric ceramic layer (11) in contact with insulation Jti (15)
The internal electrodes are connected using a pair of external electrodes (I3) so that each 1- piezoelectric ceramic (11) is connected in one layer. That is, one of the 11 inner electrodes is connected to one external electrode, and the internal electrode is connected to the other external electrode. Connect the other poles of the i-pole. Every other internal salt 41t (12) is connected to the external electrode (13) by an insulating protective film (14) as in the conventional case. In addition, a rieet wire (5) is connected to the external electrode (13) in order to conduct the electrical output to the outside. Since there is no need to reverse the polarization direction for every other layer, it is only necessary to attach removable polarization electrodes to the top and bottom surfaces of the device by applying a DC voltage.

The arrows in Figure 1 indicate the direction of polarization, and piezoelectric ceramics (
11) are polarized in the same direction, and polarization does not occur in the insulating layer (15), or even if it occurs, only weak polarization occurs. During polarization, the polarization shield should be insulated and protected by coating the top and bottom surfaces of the element to avoid direct contact with the internal salt & (12), or by sandwiching an insulating plate. (12) to prevent the polarization electrodes from shorting each other.

FIG. 2 is a partially cross-sectional perspective view showing a second embodiment of the present invention. This embodiment is a laminated type in which thin ring-shaped piezoelectric ceramic layers and insulating layers are alternately stacked in the direction of thickness. It is a piezoelectric ceramic element. Components corresponding to those in FIG. 1 are designated by the same reference numerals, and their explanation will be omitted. To polarize an element having such a structure, it is sufficient to attach polarization electrodes to the inner and outer walls of the element and apply an electric field in the radial direction as shown by the arrows in the figure. However, the inner and outer walls of the element to which the polarization electrodes are attached are provided with insulation protection for the same reason as in the case of FIG.

FIG. 3 shows an example of a recessed acceleration sensor using a laminated piezoelectric ceramic element according to the present invention, in which FIG. 3A is a top view and FIG. 3B is a partially sectional front view. Insulating layer (15)
And piezoelectric ceramics ha! (11) is stacked on the intersection JL,
Inside to take out electrical output! The 'lS electrode (12) is located on the laminated surface and connects the piezoelectric ceramic jti (11) sandwiched between the internal electrodes (12) in parallel.
The end face of 2) is surrounded every other layer with an insulating protective film (14), and an external electrode (13) is provided thereon. The outermost and innermost insulating layers (15) are thicker than other layers, and the outer electrode (13)
) and the weight (2), and the external 'ai electrode (13) and the support (3), so that there is enough room to prevent them from coming into contact with each other. Instead of the above, after forming the external electrode (13), the external! 1 (13) may be insulated and protected. One of the lead wires (5) is connected to the base (8) and grounded, and the other is connected to the connector (4). When acceleration is applied in the Z direction in the figure, an electrical output is generated and transmitted as a signal to the outside.

Note that the shape of the laminated piezoelectric ceramic element according to the present invention does not need to be limited to the above-described embodiments, as long as piezoelectric ceramic layers and insulating layers are alternately laminated.

〔Effect of the invention〕

As explained above, according to the present invention, the entire device can be divided into one part at a time with a pair of polarizing electrodes, which not only reduces the time required for attaching the polarizing fi electrodes and polarizing process, but also reduces the amount of time required for the polarization process. Even when the thickness is thin, there is an advantage that polarization processing can be performed without reducing the degree of polarization '41.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention, FIG. 2 is a diagram showing a second embodiment of the present invention, and FIG. 3 is a diagram showing an example of a stationary acceleration sensor using the present invention. 4 and 5 are diagrams showing two examples of conventional laminated piezoelectric ceramic elements, and FIG.
The figure is an explanatory diagram of the polarization state of the element in Figure 5, Figure 7 is a diagram showing an example of a conventional recessed acceleration sensor, and Figure 8 is an example of a piezoelectric ceramic element used in the one in Figure 7. FIG. (11)...Piezoelectric ceramic layer, (15)...Insulating material layer (insulating layer), (12)...Internal electrode, (1
3)...External electrode. Implantation Sadado Ito Hidemori Matsukuma

Claims (1)

[Claims] 1. A plurality of layers of piezoelectric ceramics and a plurality of layers of insulating material are stacked alternately, an internal electrode is formed on a surface where each of the ceramic layers and the insulating layer are in contact with each other, and the ceramic layer and the insulating layer are stacked alternately. A multilayer piezoelectric ceramic element characterized in that a pair of external electrodes are provided in which different internal electrodes among the internal electrodes exposed on the laminated surface of the layers are connected to every other internal electrode. 2. The plurality of piezoelectric ceramic layers and the plurality of insulating layers are hollow cylindrical shapes having different diameters, and the internal electrode is exposed at the end surface of the lamination of the ceramic layer and the insulating layer. Laminated piezoelectric ceramic element. 3. The multilayer type according to claim 1, wherein the plurality of piezoelectric ceramic layers and the plurality of insulating layers have the same thin ring shape, and the internal electrode is exposed on the side surface of the laminated layer of the ceramic layer and the insulating layer. Piezoelectric ceramic element.