JPH043511Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laminated piezoelectric actuator made of piezoelectric ceramics that prevents destruction of piezoelectric elements due to the presence of strain in piezoelectrically inactive parts.

Conventionally, piezoelectric actuators have attracted attention because they are smaller, lighter, and more energy efficient than electromagnetic actuators. Piezoelectric actuators include a piezoelectric bimorph type that utilizes a piezoelectric transverse effect and a stacked type that utilizes a piezoelectric longitudinal effect that allows a large amount of displacement to be obtained.

A multilayer piezoelectric actuator is manufactured by applying the manufacturing technology of multilayer ceramic capacitors. That is, ceramic powder is dissolved in an organic binder and an organic solvent to obtain a slurry. Next, a green sheet is formed on an organic film by, for example, a doctor blade method, and a two-component compound (Pd-Ag ) is further applied by printing at intervals of several tens of micrometers, and then cut into a predetermined size as shown in FIG.
Then, the electrode patterns of the upper and lower layers are stacked in layers so that they unfold 180 degrees, and then pressure is applied in the vertical direction while applying heat, and sintered in a temperature range of about 900 to 1250 degrees Celsius, and silver paste is applied on both sides. This can be obtained by forming the external electrode 3 in the following manner.

By the way, according to the device obtained through the above process, green sheets are punched out one by one and laminated in layers, and the film thickness is several tens to hundreds of μm, so the mechanical strength is low. is small and requires special consideration during work. Moreover, since it is necessary to develop the electrode pattern by 180°, there is a drawback that production efficiency is extremely reduced due to the need to pay careful attention to the alignment of each film.

Furthermore, as shown in Figure 2, since the internal electrodes are not formed over the entire surface, there are piezoelectrically inactive areas (see A in the figure), and as a result, when repeatedly driven as a piezoelectric actuator, the piezoelectric Internal stress within the element becomes non-uniform, and there is a risk that the piezoelectric element may break due to repeated fatigue.

In view of this, the main object of the present invention is to eliminate the above-mentioned drawbacks by providing rounding or chamfering to absorb internal stress at the end faces of the piezoelectrically inactive portions.

An embodiment of the present invention will be described in detail below with reference to the drawings.

First, after forming a green sheet, as shown in FIG.
Next, a conductive film that will become the internal electrodes 11 is formed by screen printing. After that, dry it if necessary.
The connection end side 12a with the next element 12 is rounded. In this case, the roundness is formed continuously so that the thickness of the element 12 gradually decreases from the starting part of the inactive part A where the internal electrodes are not overlapped toward the end face, and the thickness becomes almost zero at the end face. It is formed. Then, they are laminated and pressed one after another and sintered to form the shape shown in FIG. Although such an element 12 does not have internal electrodes formed over the entire surface, the element pieces 12A, . . . are integrated at the connecting ends. Furthermore, the actuator 20 can be obtained by forming the external electrodes 14a and 14b using silver paste or a conductive sputtered film.

FIG. 5 is a diagram showing another example of the present invention. In this example, the sintered body 15 has electrodes formed on its surface.
When bonding with an adhesive, it is also possible to chamfer 15a at a portion corresponding to the piezoelectric inactive region, and after laminating, form external electrodes.

Therefore, the same effect as in the above example can be obtained.

Note that the formation of the external electrodes is not limited to the above embodiments, but can be achieved by forming a resin, glass, or alumina film as an insulating layer, and forming the above conductive film on the top surface by sputtering. Effects similar to those of the embodiment can be obtained.

As described above, according to the present invention, in a piezoelectric actuator which has a piezoelectrically inactive portion that is laminated in layers such that internal electrodes are alternately connected to external electrodes, the piezoelectrically inactive portion is not formed with internal electrodes. Rounding or chamfering is applied continuously from the starting point to the end face to absorb internal stress, and the amount of rounding or chamfering is maximized at the end face, which not only eliminates the piezoelectric inactive area, but also reduces the Since the amount of roundness chamfering increases in proportion to the amount of inertness becoming more noticeable as the distance increases, it has the effect of completely eliminating distortion during driving of the piezoelectric actuator.

Furthermore, according to the present invention, it is possible to eliminate the need for the process of creating an internal electrode pattern in which the internal electrodes are alternately rotated by 180 degrees, unlike conventional ceramic capacitors.

[Brief explanation of the drawing]

1 and 2 are diagrams showing the structure of a conventional laminated piezoelectric actuator, FIGS. 3 and 4 are diagrams showing an example of the present invention, and FIG. 5 is a diagram showing another example of the device of the present invention. . 12... Actuator element, 12A... Element piece, 12a... Connection end side.

Claims (1)

[Claims for Utility Model Registration] In a piezoelectric actuator that has a piezoelectrically inactive portion that is laminated in layers such that internal electrodes are alternately connected to external electrodes, the beginning of the piezoelectrically inactive portion where no internal electrode is formed. A laminated piezoelectric actuator characterized in that rounding or chamfering is applied continuously from a point to an end face to absorb internal stress, and the amount of rounding or chamfering is maximized at the end face.