JPH05304324A - Piezoelectric actuator - Google Patents

Abstract

PURPOSE:To obtain a piezoelectric actuator in which relatively high operation generating power and displacement can be achieved concurrently through a simple structure. CONSTITUTION:A disc type piezoelectric element 22 is bonded to one surface of a disc type metal plate 20 except the peripheral part thereof to produce a piezoelectric unimorph 12. Two such piezoelectric unimorphs 12 are then jointed at the peripheral parts thereof through a spacer 24 while opposing the piezoelectric elements 22 each other thus producing a piezoelectric unit 14. A plurality, six, for example, of such piezoelectric units 12 are stacked sequentially in series in a tubular container 26, for example, thus constituting a piezoelectric actuator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric actuator that generates a minute (μm unit) mechanical displacement as an electric signal, and more particularly to a piezoelectric actuator used for horizontal positioning of a precision balance or the like.

[0002]

2. Description of the Related Art Generally, a piezoelectric actuator of this type is generally composed of a plurality of laminated plate-shaped piezoelectric elements, and is a laminated actuator constructed to superpose displacements of the plate-shaped piezoelectric elements in the thickness direction. Alternatively, it is composed of a bimorph formed by two piezoelectric elements in which a disc-shaped or rectangular-shaped metal plate is sandwiched and the peripheral portions are joined, and the displacement of the center portion due to the bending deformation of this bimorph is used. It is known as a bimorph actuator.

[0003]

However, the above-mentioned conventional piezoelectric actuators have the following drawbacks, respectively.

That is, first of all, the laminated actuator has a large actuation force (usually several tens to several hundreds of kg) in its structure, but has a small displacement (usually several tens of μm or less). Have some difficulties. On the other hand, the bimorph actuator has a large displacement amount (usually 300 μm) due to its structure.
m), however, it has a small actuation force (usually 10g or less)
It has the basic difficulty. For this reason, the conventional piezoelectric actuator of this type is required for a precision balance that requires a relatively large actuation force and displacement amount.
The application was basically inappropriate.

In order to solve each of the above-mentioned difficulties, for example, the former difficulty is described in JP-A-60-64.
As disclosed in Japanese Patent Publication No. 212-212, for example, an internal electrode is inserted between each laminated piezoelectric element to form a through hole in the central portion thereof, and a coupling rod is inserted into the through hole to connect the internal electrode to the internal electrode. A configuration has been proposed in which the displacement amount is increased by alternately and repeatedly applying an electric signal to repeatedly move the coupling rod (hereinafter referred to as a displacement magnifying mechanism). However, this method has the decisive disadvantage that it has a complicated structure and is extremely expensive in comparison with a conventional stacked actuator or bimorph actuator.

Regarding the latter difficulty, as disclosed in, for example, Japanese Patent Application Laid-Open No. 1-283069, a metal plate sandwiched between piezoelectric elements is provided with concentric annular grooves to reduce its rigidity. A configuration has been proposed in which the bending deformation of the bimorph is increased by setting the displacement and the displacement amount is further increased.

However, it is clear that this method further reduces the actuation generating force by reducing the rigidity of the metal plate.

Therefore, an object of the present invention is to provide a piezoelectric actuator which has a simple structure and can be constructed at a low cost, and at the same time can obtain a relatively large actuation force and displacement amount.

[0009]

In order to achieve the above object, a piezoelectric actuator according to the present invention has a disk-shaped piezoelectric element which has a peripheral edge portion on one surface of a disk-shaped metal plate. It is characterized in that two piezoelectric unimorphs that are adhered to each other are formed into one piezoelectric unit by interposing a spacer at the peripheral portion and making the respective piezoelectric elements face each other.

In this case, a plurality of each piezoelectric unit can be laminated in series.

[0011]

Each of the piezoelectric units constituting the present invention is composed of two piezoelectric unimorphs in which the same disk-shaped piezoelectric element is bonded to one surface of the disk-shaped metal plate, leaving the peripheral edge portion. Therefore, the unit exerts a relatively large displacement amount and, at the same time, exerts a relatively large actuation generation force because it has uniform rigidity of the metal plate. further,
In the piezoelectric actuator of the present invention, since a plurality of the units are laminated in series, the displacement amount can be set appropriately by appropriately selecting the number.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the piezoelectric actuator according to the present invention will be described in detail below with reference to the accompanying drawings.

Referring to FIGS. 1 to 7, a piezoelectric actuator 10 according to the present invention is basically composed of two piezoelectric unimorphs 12 bonded together to form a piezoelectric unit 14, and a plurality of piezoelectric units 14 are formed. It is configured by stacking pieces (five pieces in the figure). Hereinafter, these will be described in more detail.

First, the piezoelectric unimorph 12 is formed by adhering a disk-shaped piezoelectric element 22 to one surface of the disk-shaped metal plate 20, leaving a peripheral edge portion thereof. The piezoelectric unimorph 12 is the same as that used for an ordinary speaker or buzzer, for example.

Next, the piezoelectric unit 14 is formed by joining the two piezoelectric unimorphs 12 with the spacers 24 at their peripheral portions and the piezoelectric elements 22 facing each other. In this case, since the piezoelectric elements 22 are arranged facing each other toward the inside, damage can be prevented and at the same time reliability can be improved. In addition, the spacer 24
Can be made of plastic or a metal piece. However, if it is made of a metal piece (conductor), the advantage that the electric wiring can be simplified can be obtained. The piezoelectric units 14 may be sequentially stacked in the cylindrical container 26 (see FIG. 4), or may be stacked by forming through holes 28 in the central portions thereof and inserting the coupling rod 30 into the through holes. (See FIG. 5) Alternatively, through holes 32 are provided in the central portion and the peripheral portion, and the connecting rods 3 are provided in these through holes.
It is possible to stack by inserting 4 (see FIG. 6), or further by supporting with support rods 36 arranged at the outer peripheral edges without providing through holes (see FIG. 7). In addition, reference numeral 38 in the drawing denotes a displacement extracting member.

The operation of the piezoelectric actuator 10 according to the present invention having the above-described structure is as will be apparent from the experimental results described later (see Table 1). Since the piezoelectric unimorph 12 is formed by adhering the piezoelectric element 22 to one surface of the disk-shaped metal plate 20, a relatively large amount of displacement is exhibited. Further, since the metal plate 20 forming the piezoelectric unimorph 12 is composed of a uniform rigid body, it exerts a relatively large actuation generating force. Moreover, in the piezoelectric actuator 10 of the present invention, since the plurality of piezoelectric units 14 are laminated in series, the displacement amount can be set more appropriately.

Therefore, the above-mentioned Table 1 (experimental results) will be described.

[0018]

[Table 1]

That is, Table 1 shows one piezoelectric unit 1
Regarding No. 4, the displacement amount Δdμ and the residual displacement amount when a voltage of 0 to 50 to 0 V is applied under a load of 120 g are displayed. Here, Δd is (d1-d
2), and d1 is the height when no voltage is applied (see FIG. 2)
And d2 indicates the height at the time of application (see FIG. 3). As described above, the piezoelectric unit 14 according to the present invention has an average voltage of 82.
A displacement of 4 μm can be achieved. Furthermore, since the thickness of one piezoelectric unit 14 is 2 to 3 mm,
For example, in the piezoelectric actuator 10 of the present invention in which five of these are stacked, the total thickness thereof can be set to about 1.5 to 2 mm, and the displacement amount in this case is 2 mm.
It reaches 50 μm.

As described above, according to the present invention, a relatively large actuation force and displacement can be obtained with a simple structure, particularly without requiring a complicated and expensive displacement magnifying mechanism as in the conventional laminated actuator. The quantity can be obtained at the same time. Therefore, it can be suitably applied to applications such as a precision balance that requires such actuation force and displacement amount.

Although the present invention has been described above with reference to the preferred embodiments, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the spirit thereof.

[0022]

As described above, in the piezoelectric actuator according to the present invention, two disc-shaped piezoelectric elements are similarly bonded to one surface of the disc-shaped metal plate with the peripheral edge portion left. The piezoelectric unimorph is configured such that a spacer is provided at the peripheral portion thereof, the piezoelectric elements are opposed to each other, and the piezoelectric unimorph is bonded to one piezoelectric unit, and further, a plurality of the piezoelectric units are laminated in series. Since the unit is configured as a bimorph type actuator, a relatively large displacement amount can be obtained. Further, since the metal plate forming the piezoelectric unimorph is made of a uniform rigid body, a relatively large actuation force can be obtained. Moreover, since the plurality of piezoelectric units are stacked in series, the displacement amount can be appropriately increased.

Further, since the piezoelectric actuator of the present invention does not require a complicated and expensive displacement magnifying mechanism as in the conventional laminated actuator, it has an advantage in that it has a simple structure and can be provided at low cost. Have.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a piezoelectric unimorph that constitutes a piezoelectric actuator according to the present invention.

FIG. 2 is a plan view showing an embodiment of a piezoelectric unit constituting the piezoelectric actuator according to the present invention and showing a state when no voltage is applied.

3 is a plan view showing a state of the piezoelectric unit shown in FIG. 2 when a voltage is applied.

FIG. 4 is a cross-sectional view showing an example of a piezoelectric actuator according to the present invention, which is configured by stacking the piezoelectric units shown in FIGS. 2 and 3.

5 is a sectional view showing another embodiment of the piezoelectric actuator according to the present invention, which is similar to FIG.

FIG. 6 is a plan view showing still another embodiment of the piezoelectric actuator according to the present invention.

FIG. 7 is a plan view showing another embodiment of the piezoelectric actuator according to the present invention.

[Explanation of symbols]

10 Piezoelectric Actuator 12 Piezoelectric Unimorph 14 Piezoelectric Unit 20 Metal Plate 22 Piezoelectric Element 24 Spacer 26 Cylindrical Container 28 Through Hole 30 Coupling Rod 32 Through Hole 34 Coupling Rod 36 Supporting Rod 38 Displacement Extracting Member

Claims (2)

[Claims] 1. A pair of piezoelectric unimorphs formed by adhering a disk-shaped piezoelectric element to one surface of a disk-shaped metal plate while leaving a peripheral edge of the disk-shaped metal plate. A piezoelectric actuator, characterized in that one piezoelectric unit is formed by opposing piezoelectric elements. 2. A piezoelectric actuator formed by stacking a plurality of the piezoelectric units according to claim 1 in series.