JPH03251086A - Piezoelectric actuator - Google Patents

Abstract

PURPOSE:To obtain an ultrasonic wave motor having simple structure by shifting the positions for forming electrodes on the inner and outer circumferential faces and applying a voltage onto the electrodes from a single power source. CONSTITUTION:Electrodes 21, 22 are formed on the inner circumferential face of a tubular piezoelectric ceramics 20 over the semicircle and electrodes 23, 24 are formed on the outer circumferential face over the semicircle. The electrodes 21, 22 on the inner circumferential face are shifted by about 45 deg. from the electrodes 23, 24 on the outer circumferential face. AC power is applied from a power source 25 onto these electrodes thus operating an ultrasonic wave motor.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a piezoelectric actuator, and in particular, a piezoelectric actuator in which drive electrodes are formed on the inner and outer surfaces of a cylindrical piezoelectric ceramic, and the displacement generated on the end face is utilized. This invention relates to a piezoelectric actuator.

[Prior art]

Piezoelectric actuators and piezoelectric motors have the advantage of being able to be driven with low current, and are being used in a variety of fields. There are many types, including those that obtain linear motion and those that obtain rotational motion.

〔assignment〕

However, piezoelectric actuators generally have problems such as a complicated structure, a large number of parts, and a complicated circuit for driving the piezoelectric actuator.

The present invention provides a piezoelectric actuator that can be driven with a single power source without any phase difference.

[Means to solve the problem]

The present invention solves the above problems by improving the arrangement of electrodes.

That is, in a piezoelectric actuator in which at least two drive electrodes are formed on the inner and outer surfaces of a cylindrical piezoelectric ceramic, the positions of the electrodes on the inner surface and the electrodes on the outer surface are shifted, and the same power source is used. It is characterized in that it includes means for applying a voltage to at least two electrodes, one on the inner surface and one on each of the outer surfaces.

Further, the present invention is characterized in that it utilizes the displacement produced on the end face of the cylindrical piezoelectric ceramic cap.

A further feature is that the direction of rotation can be changed by switching the connection of the voltage application means.

[Effect]

The operation of the piezoelectric actuator according to the present invention has not yet been fully elucidated. However, it is believed that the operation of the piezoelectric actuator according to the present invention can be obtained by providing a substantial phase difference between the internal and external facing electrodes.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of a cylindrical piezoelectric ceramic. The outer circumference is 21.7 mm, the inner circumference is 15.5 mm, and the thickness is 6.5 m.
It is made by molding and firing a piezoelectric ceramic of m.

Uniform silver electrodes were formed on the inner and outer circumferential surfaces of the piezoelectric ceramic, and polarization treatment was performed from the inner circumference to the outer circumference.

FIGS. 2 and 3 are explanatory views of the piezoelectric ceramic in which driving electrodes are formed on the inner and outer peripheral surfaces thereof and connected to a power source.

In the example shown in FIG. 2, electrodes 21 and 22 are formed on the inner circumferential surface of a cylindrical piezoelectric ceramic 20, extending approximately half a circumference, and electrodes 23 and 24 are similarly formed on the outer circumferential surface, extending approximately half a circumference. The electrodes 21 and 22 on the inner circumferential surface and the electrodes 23 and 24 on the outer circumferential surface are not formed at the same position, and are 45"
It is formed in a staggered manner. That is, the electrode 24 on the outer circumferential surface having the opposite potential is shifted to the right by 45'' with respect to the electrode 21 on the inner circumferential surface.

In the example shown in FIG. 3, electrodes 31 and 32 are formed on the inner circumferential surface of a cylindrical piezoelectric ceramic 30, extending approximately half a circumference, and electrodes 33 and electrodes 24 are similarly formed on the outer circumferential surface, extending approximately half a circumference. The electrodes 31 and 32 on the inner peripheral surface and the electrodes 33 and 34 on the outer peripheral surface are not formed at the same position, but at a 45° angle.
It is formed in a staggered manner. That is, the electrode 34 on the outer circumferential surface, which has the opposite potential, is shifted 45 degrees to the left with respect to the electrode 31 on the inner circumferential surface.

The above structure was driven by applying a sinusoidal current, and a load of 50
A weight of 0 g was placed on the end face of the cylindrical ceramic so that their central axes were aligned, and the number of rotations was measured. The applied voltage is peak-to-peak and the thickness of the piezoelectric ceramic is 1 m.
Measured on four sides of 10V, 20V, 30V, 40V (thus 3 times that in total) per m, and the frequency is 80-8
The frequency was set to 4kHz.

Table 1 shows the measured rotational speeds of the weights.

cTable 1] Number of revolutions per minute [Table 1] Continued The above measurements were carried out using the device shown in FIG.

In the case of the electrode arrangement and connection shown in FIG. 2, the rotation was clockwise when viewed from the top, and in the case of the electrode arrangement and connection shown in FIG. 3, the rotation was counterclockwise.

Therefore, it can be rotated in any direction depending on the electrode arrangement and power supply connection, and the rotation direction can also be changed by switching the power supply connection. For this purpose, it is a good idea to divide the electrodes on the outer surface into four parts so that the power supply connection can be changed.

As shown in Table 1 above, when the frequency of the power source falls within a certain range, elliptical motion occurs on the end face of the cylindrical piezoelectric ceramic, causing the weight to rotate.

Although this frequency varies depending on the power supply voltage, the measurement results show that the highest rotational speed was recorded around 81.2 kHz when 30 V was applied per 1 mm of piezoelectric ceramic.

In addition, the current value was also measured, and although the current value also increased at higher rotational speeds, the highest rotational speed and the highest current value did not necessarily match.

Note that the arrangement (division) of the electrodes is not limited to two divisions as in the above example, but can be any number. and,
It is not necessary to apply voltage to all the electrodes, and some of them can be left floating.

When actually used as an actuator, a stator such as a metal piece is brought into contact with the end face of the cylindrical piezoelectric ceramic. The displacement (elliptic motion) of the piezoelectric ceramic transmitted to the stator can be converted into rotational motion of the rotor in contact with the stator, and the resulting energy can be utilized. Furthermore, by applying a treatment to the piezoelectric ceramic, it is also possible to bring the rotor into direct contact with the piezoelectric ceramic.

It is also possible to arbitrarily change the size of the piezoelectric ceramic and adjust the driving frequency band.

〔effect〕

According to the present invention, a piezoelectric actuator can be driven by simply applying currents of the same phase to a plurality of electrodes using a single drive power source.

Therefore, the drive circuit is simple, and assembly man-hours and costs can be reduced.

Further, rotation in both directions can be obtained arbitrarily by wiring and switching means.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an example of a piezoelectric ceramic used in the present invention, and FIGS. 2 and 3 are explanatory diagrams showing examples of electrode arrangement and power supply connection. 1O120,30...Piezoelectric ceramic 21-24.31-34...Electrode

Claims (5)

[Claims] (1) In a piezoelectric actuator in which at least two drive electrodes are formed on the inner and outer surfaces of a cylindrical piezoelectric ceramic, the positions of the electrodes on the inner surface and the electrodes on the outer surface are shifted, and the same power source is used. A piezoelectric actuator comprising means for applying a voltage to at least two electrodes, an electrode on the inner surface and each electrode on the outer surface. (2) In a piezoelectric actuator in which at least two drive electrodes are formed on the inner and outer surfaces of a cylindrical piezoelectric ceramic, the positions of the electrodes on the inner surface and the electrodes on the outer surface are shifted, and the same power source is used. A piezoelectric actuator characterized by comprising means for applying a voltage to at least two electrodes, an electrode on the inner surface and each electrode on the outer surface, and utilizing displacement generated on an end surface of the cylindrical piezoelectric ceramic. . (3) The piezoelectric actuator according to claim 2, wherein the rotary motion is obtained by bringing a rotor into contact with the end face of the piezoelectric ceramic. (4) The piezoelectric actuator according to claim 2, wherein a stator is disposed on an end face of the piezoelectric ceramic, and a rotor is brought into contact with the stator to obtain rotational motion. (5) In a piezoelectric actuator in which at least two drive electrodes are formed on the inner and outer surfaces of a cylindrical piezoelectric ceramic, the positions of the electrodes on the inner surface and the electrodes on the outer surface are shifted, and the same power source is used. It is characterized by comprising means for applying a voltage to at least two electrodes, an electrode on the inner surface and each electrode on the outer surface, and the direction of rotation can be switched by switching the connection of the voltage application means. piezoelectric actuator.