JP2684418B2 - Ultrasonic actuator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultrasonic actuator configured to convert a deformation of an ultrasonic vibrator made of a piezoelectric element into a rotational force and take out the same, and more particularly, to the ultrasonic actuator. The present invention relates to an ultrasonic actuator that converts an axial deformation of a vibrator into a motion equivalent to a so-called swinging rotation of a swash plate, and extracts the motion as a rotation output.

(Prior Art) Ultrasonic actuators that take out as rotational force by using expansion and contraction of an ultrasonic vibrator made of a piezoelectric element are small, lightweight, have high torque, and have small inertial force. Is expected to be an effective drive source for the (JP-A-58-148682, JP-A-63-5977)
(Problem to be solved by the invention) However, in the ultrasonic actuator as disclosed in Japanese Patent Application Laid-Open No. 58-148682, a progressive vibration wave is used, so that the vibration wave is not interrupted. A large number of piezoelectric elements must be circulated and installed in order to proceed, and a large number of lead wires must be installed along with this, which is still insufficient for miniaturization, weight reduction and simplification of the actuator I have to say.

Further, in a conventionally known ultrasonic actuator, since a constant proportional relationship is always maintained between the longitudinal wave amplitude and the transverse wave amplitude in principle, the longitudinal wave amplitude, which should be the driving force of the moving body, and the moving body It is difficult to freely control the amplitude of the shear wave to be the supporting force of the vehicle, and it is difficult to control the amplitude in accordance with a required change in load or speed.

On the other hand, the ultrasonic actuator disclosed in Japanese Unexamined Patent Publication No. 63-59777 is for exciting a bidirectional bending vibration wave to obtain a driving force. However, the bending actuator uses axial vibration. Although it is easy to obtain a large displacement as compared with, it is difficult to obtain a large torque on the other hand, and thus it is difficult to obtain an actuator with a large torque.

Also, if a large torque is to be obtained with this type of actuator, the voltage applied to the piezoelectric element must be increased. However, a high-voltage power supply and a high-voltage piezoelectric element are required for that, and the drive circuit becomes large. Not only that, the cost of the apparatus is greatly increased. Such problems are rooted in utilizing bending vibration.

On the other hand, the ultrasonic transducer is composed of a piezoelectric element composed of an annular disc, and the piezoelectric element is polarized so that the semicircles are positive and negative, and one piezoelectric element is provided on one side of the piezoelectric element. A ground electrode is provided, and on the other side, four 90-degree fan-shaped electrode plates are arranged in the + semicircle portion and two in the − semicircle portion. The opposing electrode plates are short-circuited to each other, and the AC voltage is applied to the two adjacent electrode plates by shifting the phase by 90 degrees, and two such annular piezoelectric elements are used. One of the inventors of the present invention has invented and is already known about an ultrasonic motor in which electrode plates are superposed so that their polarities are the same, and one distribution electrode in contact with the piezoelectric element is provided. (See Japanese Laid-Open Patent Publication No. 63-209479) An ultrasonic transducer composed of the above-mentioned known piezoelectric element is called an electrostrictive revolution element.

In this known ultrasonic motor, the rotor is rotated by utilizing the radial deformation of the ultrasonic vibrator.

Therefore, an object of the present invention is to use an electrostrictive revolution element as disclosed in JP-A-63-209479, and utilize the axial vibration of the piezoelectric element to perform so-called swinging motion of a swash plate. The goal is to obtain an ultrasonic actuator that realizes equivalent motion and that is small in size, high in output, and simple in structure.

(Means for Solving the Problem) A feature of the present invention is that a rotor, a resonator formed of an elastic material that partially contacts an end surface of the rotor and having a circular overall shape, and the resonator are provided. Of the ultrasonic transducer for axially oscillating the end surface of the ultrasonic transducer, the ultrasonic transducer comprising a piezoelectric element formed of an annular disc, and the piezoelectric element has a thickness such that the semicircles are + and −. Direction is polarized, one common ground electrode is provided on one side of the piezoelectric element, and four 90 degree fan-shaped electrode plates are provided on the other side in the + semicircle portion. And-two pieces are arranged in a semi-circle part, and among the four electrode plates, the opposite electrode plates are short-circuited, and two adjacent electrode plates are shifted in phase by 90 degrees to generate an AC voltage. A swing equivalent to the swinging motion of the swash plate is applied to the contact surface between the resonator and the rotor by applying In addition, the resonator is formed by forming four radial slits, and the resonator is divided into 90-degree fan-shaped sections, which are the same as the electrode plate. It is located radially in four parts.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

Referring to the drawing, a shaft 3 having a screw 2 is provided on a base 1 so as to project therefrom. A resonator 5 made of an elastic material is fixed to the base 1 with an ultrasonic transducer 4 interposed therebetween. Resonator 5
Is provided with a screw groove 6 into which the screw 2 of the shaft 3 is screwed, and the screw 2 of the shaft 3 is screwed into and fixed to the screw groove 6. The shaft 3 penetrates the resonator 5, and a rotor 7 is rotatably provided at the tip of the shaft 3 with a bolt 8. The bolt 8 is screwed into a screw hole 9 formed at the end of the shaft 3, and the rotor 7 is rotatably attached with the bolt 8 as a rotation shaft. A hole 10 through which the bolt 8 penetrates the rotor 7.
And a recess 11 is provided. A bearing 12 and a disc spring 13 are provided in the recess 11, and the bolt 8 is inserted through the bearing 12 and the disc spring 13. The crimping strength of the disc spring 13 changes depending on the tightening condition of the bolt 8, which causes the rotor 7 and the resonator 5 to
The crimping force with and can be adjusted.

Since the disk surface of the rotor 7 comes into contact with the resonator 5 after being deformed, it is a conical surface that is slightly inclined, and the contact surface 14 of the resonator 5 has a surface hardening treatment for preventing wear. For example, heat treatment, alumite treatment, hard chrome plating treatment, etc. are performed. The rotor 7 is not necessarily required to be tilted, but may be a flat surface as long as the rotor 7 can move in the axial direction.

The resonator 5 has a circular overall shape. Here, the circular shape includes a cylindrical shape as well as a cylindrical shape having a hole through which a shaft passes in the central portion as seen in the illustrated embodiment. Further, in this embodiment, the structure of the slit 15 is open to the contact surface where the resonator 5 and the rotor 7 come into contact with each other, but the structure is not limited to this slit structure. Further, the resonator 5 may be radially divided into four parts instead of the slits to form four 90-degree fan-shaped parts.

The ultrasonic transducer 4 is formed by subjecting the piezoelectric element 16 to a semicircle polarization to + and-, similarly to the electrostrictive revolution element disclosed in the above-mentioned Japanese Patent Laid-Open No. 63-209479. Interval-shaped 4
A single electrode plate is provided, and two electrode plates are superposed on each other and one distribution electrode 17 is in contact with the piezoelectric element 16.

The piezoelectric element 16 will be described in more detail with reference to FIG.
As shown in detail in (b), a ground electrode 18 is provided on one surface and fan-shaped electrode plates are provided at 90 degree intervals on the other surface.
19, 20, 21, and 22 are applied, a positive DC voltage is applied to the electrodes 19 and 20, and a negative DC voltage is applied to the electrodes 21 and 22 to form a semicircle as shown by + and − in the figure. The residual polarization is + and-, respectively. In this embodiment, the two piezoelectric elements 16 processed as described above have the same polarity on the four electrode plates 19, 20, 21, and 22 (the positive and negative polarities are overlapped with each other). ) Is overlaid.

In addition, the distribution electrode 17 is arranged so as to be sandwiched between the two piezoelectric elements 16 and, as shown in FIG. 3C, the electrodes which are in contact with the electrodes 19, 20, 21, 22 respectively. Board 19A, 2
It has 0A, 21A, 22A, short-circuits the electrode plate 19A and the electrode plate 21A, short-circuits the electrode plate 20A and the electrode plate 22A, and connects two lead wires 23, 24 to each. . Ultrasonic transducer 4
A lead wire 25 is provided to connect to the ground electrode 18 of the piezoelectric element 16.

The fan-shaped electrodes 19, 20, 21, 22 correspond to the fan-shaped portion of the resonator 5 defined by the slit 15.

The operation of the ultrasonic actuator of the present invention configured as described above will be described.

First, referring to FIG. 5, a so-called swash plate swinging motion will be described.

The swash plate 31 operates so that the coma just tilts and swings and swings. Here, the swash plate 31 simply swings and swings at an inclination angle θ without rotating itself, but one point on the conical surface 32 of the swash plate 31 contacts a rotor 33 at a predetermined peripheral speed ( Since it is displaced at the tangential velocity), the conical surface
The rotor 32 frictionally drives the rotor 33 at the peripheral speed. The rotating mechanism in this case is known as a speed reducing mechanism using a swash plate gear (see Japanese Patent Laid-Open No. 60-125443), and the speed reducing ratio is as follows.

That is, assuming that the inclination angle of the swinging rotation is θ, the reduction ratio is 1 / Sinθ.

Now, assuming that the displacement amount of the piezoelectric element is ΔL and the radius of the swash plate is R, ΔL is so small that Sinθ = θ, and the reduction ratio is 1 / Sinθ = 1 / θ = 1 / (ΔL / R) = It becomes R / ΔL.

Now, in the ultrasonic actuator of the present invention, when an alternating voltage of the same frequency is applied to the lead wires 23, 24 with a phase shift of 90 degrees, the electrodes 19, 20, 21 are passed through the electrode plates 19A, 20A, 21A, 22A. , 22, the piezoelectric elements 16 that are polarized expand and contract in sequence (alternately), and this vibration propagates through the resonator 5 as a longitudinal elastic vibration wave and is generated on the contact surface 14 during the swinging motion of the swash plate. A motion equivalent to the motion is produced, and the rotor 7 is rotationally driven by this.

The above is one embodiment of the present invention, and the present invention is not limited to the above embodiment.

For example, the structure of the piezoelectric element that causes the axial vibration is not limited to the above-described embodiment, and a structure in which four 90-degree fan-shaped piezoelectric elements are provided is sufficient. Instead of subjecting the annular disc to polarization treatment, four piezoelectric elements may be arranged on the circumference.

Further, in the above embodiment, two piezoelectric elements are installed, but the number of piezoelectric elements of the present invention is not limited to two, and it is needless to say that one piezoelectric element may be used. It is also possible to make more than one sheet.

Further, in the above-mentioned embodiment, the polarized parts of the piezoelectric element are overlapped so as to face each other so that only one distribution electrode plate is required. However, the ground electrode parts of the piezoelectric element are overlapped and the distribution electrode plate is divided into two parts. It is also possible to adopt a structure in which one piece is grounded.

(Effects of the Invention) The effects of the present invention described above are enhanced as follows.

Since the rotational force is extracted from the elastic vibration wave in the axial direction by the four fan-shaped piezoelectric elements, a large torque can be obtained, and a small and high-power ultrasonic actuator can be obtained, while at the same time being small and compact. Becomes

According to the configuration of the present invention, it is possible to easily overlap two or more piezoelectric elements,
It is possible to obtain a more compact and high-power ultrasonic actuator.

According to the present invention, basically only three lead wires need to be installed, so that the wiring can be simplified.

[Brief description of the drawings]

FIG. 1 is a front view of an ultrasonic actuator showing an embodiment of the present invention, FIG. 2 is an exploded view of the ultrasonic actuator of FIG. 1, and FIG. 3 (a) is a plan view of a piezoelectric element viewed from one side. Fig. 3 (b) is a plan view of the piezoelectric element viewed from the other side,
FIG. 3C is a front view showing the distribution electrode plate, FIG. 4 is a plan view of the resonator, and FIG. 5 is a diagram for explaining the swinging motion of the swash plate, which is the operation of the present invention. 1: base, 2: screw, 3: axis, 4: ultrasonic transducer, 5: resonator,
6: Thread groove, 7: Rotor, 8: Bolt, 9: Screw hole, 10: Hole, 11:
Recess, 12: bearing, 13: disc spring, 14: contact surface, 15: slit,
16: Piezoelectric element, 17: Distribution electrode 18: Ground electrode, 19, 20, 21, 22: Electrode 19A, 20A, 21A, 22A: Electrode plate 23, 24, 25: Lead wire

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-209479 (JP, A) JP-A-63-110980 (JP, A) JP-A-63-140679 (JP, A) JP-A 64-- 1482 (JP, A) Actually opened 63-70297 (JP, U)

Claims (4)

(57) [Claims] 1. A rotor, a resonator made of an elastic material which is in partial contact with an end surface of the rotor and formed into a circular shape as a whole, and an ultrasonic vibrator for vibrating the end surface of the resonator in an axial direction. The ultrasonic transducer is composed of a piezoelectric element formed of an annular disc, and the piezoelectric element is polarized in the thickness direction so that the semicircles are + and −, and one of the piezoelectric elements is formed. One side has a ground electrode, and the other side has a 90 degree fan shape.
Two electrode plates are arranged in the + semicircle portion and two in the − semicircle portion, and among the four electrode plates, opposing electrode plates are short-circuited to each other, and two adjacent ones are formed. By applying an alternating voltage by shifting the phase of the electrode plate by 90 degrees, an oscillating rotation equivalent to the swinging motion of the swash plate is generated at the contact surface between the resonator and the rotor. Sonic actuator. 2. The ultrasonic actuator according to claim 1, wherein four radial slits are formed in the resonator, and the resonator is partitioned into a fan shape of 90 degrees which is the same as the electrode plate. . 3. The ultrasonic actuator according to claim 2, wherein the slit formed in the resonator is opened to a contact surface which comes into contact with the rotor. 4. The ultrasonic actuator according to claim 1, wherein the resonator is radially divided into four parts, and the resonators are arranged in a fan shape having the same 90 degrees as the electrode plate.