JP2759804B2 - Vibrator type actuator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator suitable for transporting a card such as a bank card in a machine for reading the card, and more particularly to a piezoelectric actuator as an electromechanical transducer. The present invention relates to a vibrator-type actuator using a vibrator.

(Prior art and problems) Among vibrator-type actuators using a piezoelectric vibrator as electromechanical conversion means for converting electric energy into mechanical energy, an ultrasonic motor is well known. Ultrasonic motors are characterized by lower rotational speed and higher torque than electromagnetic motors that rotate by electromagnetic force, so they are widely used as actuators for precision machinery. The mechanical structure of the vibrator and the like and the electric circuit for exciting the piezoelectric vibrator are complicated, difficult to miniaturize, and expensive.

A vibrator-type actuator that can be easily miniaturized and can be manufactured at low cost is the “vibrator-type actuator” invented and patented by the same inventor of the present invention (Japanese Patent Application No. 63-12)
9122, 63-157506). The piezoelectric vibrator used in the vibrator-type actuators of these patent applications is a columnar type, but a rectangular piezoelectric vibrator is often easier and more convenient for some applications.

The piezoelectric vibrator has a rectangular shape (square plate or prism shape), and the following ultrasonic motors have been published so far.

Using the in-plane flexural vibration mode (Flexural-Flexuralmode) of a square plate with the same shape and degeneracy (Bucheon)
Others: “Ultrasonic motor using in-plane vibration multimode transducer”, US87-32 (1987)).

Two vertical vibrations (Be
nding-Bendingmode) to obtain an elliptical motion (Tomikawa et al .: “Ultrasonic motor configuration and its application”, US87-5 (1987)).

No characteristic results have been reported for these two types.

An ultrasonic linear motor (Taniguchi, Shimizu: “Piezoelectric ceramics”) that uses strips of electrodes on a prism (square bar) of a single piezoelectric ceramic and uses the same degenerate dual-mode flexural vibrator to polarize and excite the electrodes. "Sound-piece type ultrasonic linear motor", Sound Lectures, 62.10).

Elliptical motion drive: Max. Speed 16cm / s, maximum thrust 60gw when input 141V, 0.89W, f = 21.7kHz Linear motion drive: Max. Speed 7.6cm / when input 283V, 0.93W, f = 22.3kHz s, maximum thrust 75 gw FIG. 4 is a view for explaining the above ultrasonic motor,
FIG. 1A is a perspective view of a piezoelectric vibrator, FIG. 2B is a conceptual diagram showing directions of polarization and excitation in the piezoelectric vibrator, and FIG. 1C is a conceptual diagram showing a vibration mode in the piezoelectric vibrator. (D) and (e) are a plan view and a side view of the ultrasonic motor, respectively.

However, in the above ultrasonic motors, the mechanical structure such as the piezoelectric vibrator and the electric circuit for exciting the piezoelectric vibrator are complicated, and there are difficulties in downsizing and cost reduction.

Therefore, an object of the present invention is to provide a vibrator-type actuator that has a simple structure, can be easily miniaturized, can be manufactured at low cost, and has a rectangular piezoelectric vibrator.

(Means for Solving the Problems) Means provided by the present invention for solving the problems described above operate on the basis of a piezoelectric vibrator and a vibration displacement caused by applying an AC voltage to the piezoelectric vibrator. A vibrator-type actuator including a mover, wherein the piezoelectric vibrator has a rectangular parallelepiped ceramic piezoelectric body having at least two of length, width, and height substantially equal to each other, and a polarization axis of the ceramic piezoelectric body. A pair of electrodes fixed to two end surfaces perpendicular to the first electrode, one of the pair of electrodes is composed of an electrode A and an electrode B electrically insulated from each other, and the piezoelectric vibrator is The AC voltage having a frequency substantially equal to one of the resonance frequencies of the first and second electrodes is applied between the other of the pair of electrodes and the electrode A or the electrode B. In one direction parallel to the polarization axis or in the other direction opposite to the polarization axis, the vibration displacement serving as a power source of the movable element is generated, and the movable element is connected to the ceramic piezoelectric body in a direction parallel to the polarization axis. Contacting at least one of the side surfaces.

(Example) Next, the present invention will be described in detail with reference to examples.

FIG. 1 is a perspective view showing one embodiment of the present invention. This embodiment includes a piezoelectric vibrator 1, a rotor 2, and pressure contact means (not shown) for pressing the rotor 2 against the piezoelectric vibrator 1. The piezoelectric vibrator 1 is made of a ceramic piezoelectric body 11.
And electrodes 12, 13a, 13b, and the rotor 2 is provided with a rotating shaft 21. The electrodes 13a and 13b are insulated from each other. In this embodiment, one of the pair of electrodes is divided into 13a and 13b. The shape of the piezoelectric body 11 is a cube having a side of 5 mm. When the Young's modulus is Y ₃₃ ^E (N / m ² ), the density is ρ (kg / m ³ ), and the Poisson's ratio is σ, the material constants of the piezoelectric body 11 are Y ₃₃ ^E = 7.7 × 10 ¹⁰ and ρ = 7.6 × 10 ³ , σ = 0.28
It is. The polarization axis of the piezoelectric body 17 is in a direction perpendicular to the electrodes 12, 13a, 13b.

FIG. 2, when the frequency f is applied an AC voltage of 233.2KH _Z between the electrode 12 and the 13a of FIG. 1 embodiment, the vibration displacement generated on the surface of the piezoelectric member 11 of the embodiment by the arrow FIG. The vibration displacement in the directions of the X axis and the Z axis occurs in the direction opposite to that in FIG. 2 when an AC voltage is applied between the electrodes 12 and 13b. However, the vibration displacement in the Y-axis direction is the same as that in FIG. 2 even if the electrode to which the voltage is applied is changed from 13a to 13b.

FIG. 3 shows the piezoelectric vibrator 1 in the embodiment of FIG.
FIG. 9 is a frequency characteristic diagram of admittance indicated by the piezoelectric vibrator when an AC voltage of up to 600 kHz is applied. As is clear from this figure, the piezoelectric vibrator 1 resonates at the frequencies f ₁ , f ₂ and f ₃ , and large vibration displacement appears at these frequencies. Part f ₁ is 233.2KH _Z, when exciting the piezoelectric vibrator 1 at this frequency, the vibration displacement occurs as shown by the arrow in Figure 2 as previously described.

The embodiment shown in FIG. 1 is an actuator for extracting the vibration displacement shown in FIG. 2 as a rotational force, and the rotor 2 rotates around a rotation shaft 21 in the direction of the arrow in FIG. Of course, rotor 2
Can be changed in the direction opposite to the arrow in FIG. 1 by switching and applying an alternating voltage for excitation to the electrodes 13a to 13b.

FIG. 1 does not show a means for stably bringing the rotor 2 into contact with the piezoelectric body 11, but for example, the bearing of the rotating shaft 21 may be pressed in the direction of the piezoelectric body 11 by a spring. Therefore, detailed description is omitted.

By adopting the structure in which the rotor 2 of FIG. 1 is brought into contact with a card, the present embodiment can be used for an automatic cash withdrawal machine of a bank. It is to be noted that a hard material such as hard plastic or metal is suitable for the rotor 2, and direct contact with the card may damage the card. In order to eliminate such a risk, a second rotor made of rubber or the like may be provided, the rotation of the rotor 2 may be transmitted to the second rotor, and the second rotor may be brought into contact with the card.

In the first embodiment, the excitation AC voltage is kept single-phase, and only the electrodes to be applied are switched between 13a and 13b.
Since the rotation direction of the piezoelectric vibrator can be arbitrarily changed, the excitation circuit of the piezoelectric vibrator is simple.

(Effects of the Invention) As described above in detail with reference to the embodiments, in the present invention, the shape of the piezoelectric vibrator is a rectangular shape, which is easy to mount on a device, the structure is simple, and the piezoelectric vibrator is small (the example is 5 mm on a side). And a smaller rotor). Therefore, the actuator of the present invention can be manufactured at low cost. In addition, since the moving direction of the movable element can be arbitrarily changed only by switching the voltage application electrode with the single-phase AC for exciting the piezoelectric vibrator, the configuration of the piezoelectric vibrator exciting circuit can be simplified.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, and FIG.
FIG. 3 is a conceptual diagram showing a vibration displacement appearing in the piezoelectric vibrator 1 in the embodiment of the present invention, FIG. 3 is a characteristic diagram showing a frequency-admittance relationship of the piezoelectric vibrator 1 in the embodiment of FIG. 1, and FIG. FIG. 2 is a diagram illustrating an ultrasonic motor that is a type of actuator. Reference numeral 1 denotes a piezoelectric vibrator, 2 denotes a rotor, 11 denotes a ceramic piezoelectric body, 12, 13a, 13b denotes an electrode, and 21 denotes a rotating shaft of the rotor.

Claims (1)

(57) [Claims] 1. A vibrator-type actuator comprising: a piezoelectric vibrator; and a moving element that operates based on a vibration displacement generated by applying an AC voltage to the piezoelectric vibrator; A ceramic piezoelectric body formed into a rectangular shape having at least two of the heights substantially equal to each other, and a pair of electrodes fixed to two end surfaces perpendicular to the polarization axis of the ceramic piezoelectric body, One of the electrodes includes an electrode A and an electrode B electrically insulated from each other, and the piezoelectric vibrator applies the AC voltage having a frequency substantially equal to one of the resonance frequencies of the piezoelectric vibrator to the pair of AC voltages. Is applied between the other one of the electrodes and the electrode A or the electrode B, so that one direction parallel to the polarization axis or another direction reverse thereto. The vibration displacement acting as a power source of the moving element is generated, wherein the moving element is in contact with at least one of four side surfaces of the ceramic piezoelectric body parallel to the polarization axis. A vibrator-type actuator.