JPH03270085A - Laminated piezoelectric actuator element - Google Patents

Abstract

PURPOSE:To improve reliability of a laminated piezoelectric actuator element and to obtain an element having small deviation loss, deviation distribution and internal stress by stacking a plurality of laminated longitudinal effect piezoelectric element subunits, and reducing the area of a junction member for bonding between adjacent subunits equal to or smaller than the area of inner electrodes. CONSTITUTION:A laminated piezoelectric actuator element 10 is composed of a laminated longitudinal effect piezoelectric element subunit 5, a junction member 3 for bonding adjacent subunits, and outer electrodes 6 for supplying a drive voltage to a piezoelectric ceramic layer 2. In the unit 5, an inner electrode layer 1, outer electrodes 6 and an electrode lead 11 are screen printed on the layer 2 of substantially square-shaped lead titanate-zirconate, and laminated. A piezoelectric inactive part 7 in which the drive voltage is not applied exists on the periphery of the subunit 5. Since the number of laminated layers is small, control of the thickness of the layer, the uniformity of crystal grain size and the denseness in the case of sintering are facilitated, and decreases in reliability of piezoelectric properties, insulating properties are entirely eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laminated piezoelectric actuator element used in piezoelectric actuators and the like.

[Prior Art] Conventionally, this type of laminated piezoelectric actuator element is
A structure in which lead zirconate titanate (PZT)-based piezoelectric ceramic layers and internal electrode layers are alternately laminated in the direction of expansion and contraction has been proposed. Such a laminated piezoelectric actuator element expands and contracts depending on the polarity of the voltage applied to the internal electrode layer, so its displacement can be used as an actuator for piezoelectric dot impact printer heads, VTR heads, etc., and also for ultrasonic motors. It is used as a vibrator. In addition, if the thickness of one layer of the piezoelectric ceramic layer becomes several tens of micrometers or less, the insulation between internal electrode layers becomes a problem. A laminated piezoelectric ceramic element having an internal electrode structure in which an inactive portion exists has been manufactured.

[Problems to be Solved by the Invention] In order to achieve low-voltage driving of the laminated piezoelectric actuator element as described above, it is required to reduce the thickness of each layer of laminated piezoelectric ceramic layers and increase the number of laminated layers. There is. However, the thinner the thickness of each piezoelectric ceramic layer or the greater the number of laminated layers, the greater the risk of damage to the degreasing body during the degreasing process and non-uniformity of the piezoelectric ceramic layer during sintering. , there was a problem of decreased reliability. In addition, in a laminated piezoelectric ceramic element having an internal electrode structure in which a so-called piezoelectrically inactive area without an internal electrode layer exists in the peripheral area of the piezoelectric ceramic layer, the piezoelectrically inactive area acts to restrain displacement when a voltage is applied. This caused problems such as displacement loss, displacement distribution, and internal stress.

The present invention has been made in order to solve the above-mentioned problems, and its purpose is to stack a plurality of laminated longitudinal effect piezoelectric element subunits each having an internal electrode structure having a piezoelectrically inactive portion at the periphery. By making the area of the bonding member that connects adjacent laminated longitudinal effect piezoelectric element subunits less than or equal to the area of the internal electrode, the reliability of the low-voltage-driven laminated piezoelectric actuator element is improved, and piezoelectric The object of the present invention is to provide a highly reliable laminated piezoelectric actuator element that is driven by a low voltage and has low displacement loss, displacement distribution, and internal stress by reducing the effect of an inert part restraining displacement.

[Means for Solving the Problems] In order to achieve this object, the laminated piezoelectric actuator element of the present invention generates dimensional strain due to the piezoelectric/electrostrictive longitudinal effect by applying a voltage. The area of the joint for connecting the laminated longitudinal effect piezoelectric element subunit with the internal electrode structure having a piezoelectrically inactive part in the peripheral part and the adjacent laminated longitudinal effect piezoelectric element subunit is the area of the internal electrode layer. A plurality of the laminated longitudinal effect piezoelectric element subunits are stacked with the bonding member interposed in a direction in which longitudinal effect dimensional distortion occurs.

[Operation] According to the laminated piezoelectric actuator element of the present invention having the above-mentioned configuration, a laminated longitudinal effect piezoelectric element subunit having an internal electrode structure having a piezoelectrically inactive portion at the periphery is connected to the adjacent laminated longitudinal effect piezoelectric element. A plurality of subunits are stacked in a direction that produces longitudinal effect dimensional distortion through a joining member whose area of the joining part for joining the subunits is less than or equal to the area of the internal electrode layer, and a desired driving voltage is applied. Displace.

[Example] An example embodying the present invention will be described with reference to FIGS. 1 and 2. The laminated piezoelectric actuator element 10 includes a laminated longitudinal effect piezoelectric element subunit 5, a joining member 3 for joining adjacent laminated longitudinal effect piezoelectric element subunits,
It is composed of an external electrode 6 for supplying a driving voltage to the piezoelectric ceramic layer 2.

The laminated longitudinal effect piezoelectric element subunit 5 has a thickness of 20 μm.
The area is 3. OX3. 0 mm, and is electrically connected to a substantially square-shaped lead zirconate titanate (PZT)-based piezoelectric ceramic layer 2 with a substantially square-shaped internal electrode layer 1 and external electrode 6 with an area of 2.5 x 2.5 mm. After screen printing the electrode take-out portions 11, 23 sheets were laminated.

The height of the laminated longitudinal effect piezoelectric element subunit 5 is 0.5 mm.
Consists of. The laminated longitudinal effect piezoelectric element subunit 5
There is a piezoelectric inactive region 7 having a width of about 0.25 mm and to which no driving voltage is applied.

The ten laminated longitudinal effect subunits 5 have an area of 2,
If they are joined together via a 5 x 2.5 mm square joining member 3 made of an organic adhesive, a laminated piezoelectric actuator element 10 having a slit 4 with a width of about 0.25 mm around the periphery of the joining member 3 is formed. Ru.

In the laminated longitudinal effect piezoelectric element subunit 5 of this example, the thickness of each piezoelectric ceramic layer 2 is extremely thin at 20 μm, but since the number of laminated layers is as small as 23, the thickness of the layers, the uniformity of the crystal grain size, and the It is easy to control sintering such as densification, and there is no reduction in reliability of piezoelectricity or insulation properties. Furthermore, since the number of laminated longitudinal effect piezoelectric element subunits having thin piezoelectric ceramic layers with a thickness of several tens of μm can be arbitrarily selected, a highly reliable laminated longitudinal effect piezoelectric element subunit can be obtained, and the laminated piezoelectric The reliability of the entire actuator element is also improved. Further, since this laminated longitudinal effect piezoelectric element subunit has a portion without an internal electrode layer in the peripheral portion, the reliability of the insulation between the internal electrode layers is high and the moisture resistance is also good.

Laminated piezoelectric actuator element 1 configured as above
0 is 7 as a result of applying a driving voltage of 60V to the external electrode 6.
A displacement of μm was obtained. In another embodiment, 10 of the stacked longitudinal effect subunits 5 have an area of 2. OX2. Omm
In the laminated piezoelectric actuator element 10, which is connected via a joining member 3 of
As a result of applying a driving voltage of V, a displacement of 8 μm was obtained.

A laminated piezoelectric actuator element in which 10 laminated longitudinal effect piezoelectric element subunits 5 prepared as a comparative example were fully bonded, and 10 laminated longitudinal effect subunits 5 were combined with a bonding member 3 having an area of 2.7 x 2.7 mm. In the laminated piezoelectric actuator element 10 which has a slit 4 with a width of about 0.15 mm at the periphery of the bonding member 3, as a result of applying a driving voltage of 60 V to the external electrodes 6, the width of each 4.8 μm 1
A displacement of only 5 μm was obtained.

Therefore, it can be seen that when the area of the bonding member 3 is less than or equal to the area of the internal electrode layer 1, the presence of the slit 4 reduces the effect of the piezoelectrically inactive portion restraining displacement. Also,
Due to the presence of the slit 4, internal stress generated during driving can be alleviated, and mechanical destruction of the element can also be prevented. Therefore, a multilayer piezoelectric actuator element with high reliability and low voltage drive can be obtained. As a result, when using the laminated piezoelectric actuator element of the present invention as a drive source for an impact-type piezoelectric printer head, for example, it becomes possible to significantly reduce the voltage and use the same power source as the motor, etc. It is possible to downsize the printer device and reduce costs.

[Effects of the Invention] As is clear from the detailed description above, the laminated piezoelectric actuator element of the present invention achieves highly reliable low voltage drive by stacking the laminated longitudinal effect piezoelectric element subunits. A laminated piezoelectric actuator element is obtained.

Further, since this laminated piezoelectric actuator element has a portion without an internal electrode layer in the peripheral portion, the reliability of the insulation between the internal electrode layers is high and the moisture resistance is also good. By making the area of the bonding member that connects adjacent laminated longitudinal effect piezoelectric element subunits less than or equal to the area of the internal electrode layer and having grooves in the periphery of the bonding member, when voltage is applied, The piezoelectric inactive portion reduces the effect of restricting displacement, reduces displacement loss and internal stress, reduces drive voltage, and suppresses element destruction.

[Brief explanation of drawings]

1 to 2 show embodiments embodying the present invention. FIG. 1 is a schematic configuration diagram showing a laminated piezoelectric actuator element, and FIG. 2 is an internal electrode layer pattern on a piezoelectric ceramic layer. FIG. l...Internal electrode layer 3...Joining member 4...Slit

Claims (1)

[Claims] In a laminated piezoelectric actuator element that generates dimensional strain due to piezoelectric/electrostrictive longitudinal effect by application of a voltage, a laminated longitudinal effect piezoelectric element sub having an internal electrode structure having a piezoelectrically inactive portion at the periphery. unit, and a joining member for joining the laminated longitudinal effect piezoelectric element subunits, the area of the joint part for joining the laminated longitudinal effect piezoelectric element subunits being equal to or less than the area of the internal electrode layer, 1. A laminated piezoelectric actuator element, characterized in that a plurality of piezoelectric actuator elements are stacked with the joining member interposed in a direction that produces an effect of dimensional distortion.