JPH10225153A - Ultrasonic motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic motor which can be manufactured at low cost and therefore has high productivity. SOLUTION: First piezoelectric elements 2a, 2b of a main vibrating system and second piezoelectric elements 3a, 3b of a switching system are all polarized in the same direction. Driving members 4a, 4b for driving a rotor are fixed at the centers of the second piezoelectric elements 3a, 3b located on a concentric circle. By switching the serially connected first piezoelectric elements 2a, 2b to the parallelly connected second piezoelectric elements 3a, 3b respectively, a node line of vibration can be displaced and thereby the movements of the driving members can be changed to change the turning direction of the rotor. As the piezoelectric elements are all polarized in the same direction, the productivity can be increased. Cutout sections 5a, 5b formed in the periphery on an extension line connecting the driving members 4a, 4b secures the displacement of the node line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor, and more particularly, to an ultrasonic motor having a piezoelectric element for applying ultrasonic vibration to a driver for rotationally driving a rotor serving as a load. is there.

[0002]

2. Description of the Related Art FIG. 4 is proposed by the present inventor (Japanese Patent Application No. Hei 8-11).
5210) is a conventional ultrasonic motor, in which, in the figure, first piezoelectric elements 12a and 12b, which are arranged in even numbers on a disk-shaped substrate 11 made of an elastic body such as metal and are arranged in different polarization directions, An ultrasonic transducer is formed by two sets of second piezoelectric elements 13a, 13b and 14a, 14b having different polarization directions, and two drivers 15a, 15b for pressing a rotor (not shown) to the ultrasonic transducer. They are fixed at fixed intervals. With the above configuration, one of the sets of the second piezoelectric elements is switched in parallel with the first piezoelectric elements 12a and 12b to generate ultrasonic vibrations, thereby rotating the rotor to the left or right.

[0003]

In the conventional ultrasonic motor as described above, the polarization operation of the evenly divided piezoelectric elements is different from each other, so that it is difficult to perform the polarization operation, thereby increasing the cost. In addition, since one of the sets of the second piezoelectric element of the switching system always plays without participating in vibration, a reduction in efficiency is unavoidable, and vibration is unstable. The present invention seeks to solve the above problems,
An object is to obtain an efficient and stable ultrasonic motor having excellent mass productivity.

[0004]

An ultrasonic motor according to the present invention comprises an even number of first piezoelectric elements in a main vibration system and a second piezoelectric element in a switching system for each one piezoelectric element. Thus, any one of a disk, a ring, and a cylinder is formed, the polarization directions of the first and second piezoelectric elements are all the same, and switching of the second piezoelectric element connected in parallel to the first piezoelectric element is performed. Accordingly, the node line of the main vibration system is biased to one of both sides of the driver to change the rotation direction of the rotor.

An ultrasonic motor according to another aspect of the present invention, in addition to the above-described configuration, provides a notch such as a semicircle on an outer peripheral portion on an extension of a driver arrangement line to perform a displacement operation of a node line. Sure.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) An embodiment will be described with reference to FIGS. 1, 2 and 3. FIG. In FIG. 1, a first piezoelectric element 2a, 2b of a main vibration system is provided on a disk-shaped substrate 1 made of an elastic body such as a metal.
The second piezoelectric elements 3a and 3b of the switching system are alternately and
Each is symmetrically attached to the center of the circle. These piezoelectric elements are all polarized in the same direction. The piezoelectric element may be individually attached or a single-plate type by a known technique, or may be without a substrate. The polarity of the piezoelectric element may be either (+) or (-). The driving elements 4a and 4b include a piezoelectric element 3a,
3b is fixed at a concentric distance in the central portion. The side on which the driver is mounted may be on the piezoelectric element, or may be simultaneously processed by brazing or pressing at the same position on the back surface. Semicircular notches 5a and 5b are formed in the outer peripheral portion of the driver 4a and 4b installation line extension lines to stabilize the absorption of the resonance node line at the time of switching. The shape of the notch may be triangular (wedge-shaped), trapezoidal, rectangular, or simply cut off in addition to a semicircle, and is effective in stabilizing the position of the node line during vibration.

Next, the operation will be described. In FIG. 1, when a current is applied to the piezoelectric elements 2a and 2b of the main vibration system polarized in the same polarity in series to resonate, the node line appears just on the line A1-A2 on the driver. The vibration mode at this time is such that when the area of the piezoelectric element 2a bends upward, the piezoelectric element 2b
Area will bend downward. The movement of the driver 4b at this time is shown in FIG. The X1-X2 arc line is obtained by extending a concentric circle on the driver 4b straight, and node lines generated at the time of switching are indicated by B1-B2 and C1-C2. Now, as a resonance state diagram at the time of series connection in which only the piezoelectric elements 2a and 2b are operated, FIG. 2A shows the moment when the area of the piezoelectric element 2a is bent upward and the area of the piezoelectric element 2b is bent downward. That is, in the state where the switching system piezoelectric elements 3a and 3b are not energized, the node line is A
The driver 4b simply swings left and right on A1-A2 to occur on 1-A2.

Next, in FIG. 2B, the piezoelectric elements 2a and 3
b, a case where the respective groups in which the piezoelectric elements 2b and 3a are arranged in parallel are connected in series and input. That is, this time, the node line is generated on C1-C2 corresponding to the boundary line between the two groups, so that the piezoelectric element 2a
-3b area is bent upward, and the piezoelectric element 2b-3a area is bent downward. Therefore, the driver 4b is lifted upward and swings its head toward the piezoelectric element 2b, so that the rotor in contact with the distal end of the driver receives a force in the direction of the arrow (the piezoelectric element 2b). At this time, the driver 4
Since a is inclined toward the piezoelectric element 2a, the rotor rotates clockwise in FIG. The next half cycle behavior is
Both the drivers 4a and 4b sink away from the rotor.

[0009] In order to reverse the rotor, the connection in FIG.
a, 3a and the piezoelectric elements 2b, 3b may be switched to generate a node line on B1-B2. As described above, the switching of the rotation direction of the rotor is determined by which side the second piezoelectric elements 3a and 3b of the switching system are switched to, and the swing of the vertical component and the rotation direction component of the driver at this time. The length can be adjusted by the angle of the separation θ between the piezoelectric elements 3a and 3b.

The notches 5a and 5b are provided to stabilize each vibration at the time of switching and to fix the position where the node line is generated. This notch is effective even if it is applied to a conventional one as shown in FIG. As shown in FIG.
Since the left and right rotation can be arbitrarily selected by switching the SW, the entire area of the piezoelectric element can be always effectively involved in the vibration, so that a highly efficient motor can be designed without waste.

(Other Embodiments) In the first embodiment, the explanation has been given of the case of 1/2 division which is a simplified illustration, but the number of divisions is increased to 1/4, 1/6,. . . . The operation principle is the same. When the number of divisions is large, the number of driver elements and the cutouts may be omitted by appropriately thinning them out. In the first embodiment, the example in which the piezoelectric element is adhered to one surface of the substrate is shown. However, if the piezoelectric element is adhered to both the front and back surfaces and used so as to bend in the same direction, low voltage driving becomes possible. Especially in the design of micro motors,
A proportional reduction type of only the piezoelectric element in which the substrate 1 is omitted is suitable.

In the construction of the ultrasonic motor, the center hole is often used for assembling and fixing the vibrator unit including the substrate 1 which is generally on the stator side. However, in the motor according to the present invention, the cutout provided on the outer peripheral portion is used. By utilizing the notched portion, positioning assembly that also serves as a rotation stopper can be performed. When the substrate 1 is a conductive material such as a metal plate, the back side electrodes are electrically connected to each other by sticking the piezoelectric element. If this is inconvenient, the back side electrodes are electrically separated by inserting an insulating layer. When the substrate is made of an insulating material such as glass or a ceramic material, there is no need for a folded electrode as it is.
The material and dimensions of the driver, the angle of θ, and the shape of the notch are determined in accordance with the combination with the rotor material and the application.

Since the present invention is applicable to all endless shapes, the piezoelectric element structure may be formed in a ring shape (donut shape) or a cylindrical shape. In the case of an annular shape, X in FIG.
The ring along the 1-X2 line may be cut out at a certain width, and the number of divisions may be increased as appropriate according to the diameter and thickness. The switching of the direction and the installation of the notch are the same, and the piezoelectric element can be configured so that the bending direction is matched to the front and back surfaces. In the case of a cylindrical shape, the rotor is generally arranged inside the cylinder, so that the piezoelectric material is attached to the outer surface of the cylinder. The operation is exactly the same.While each circular sector of the disk oscillates up and down, each circular sector oscillates up and down. In this case, the behavior in which the bending vibration in the outside and the bending in the inside match. The mounting of the piezoelectric material includes a PZT thin film by a sol or gel method and a ZnO thin film by a sputtering method in a small motor. Both the annular and cylindrical vibration units can be operated stably by providing a notch along the vicinity of the driver installation line, and there is no restriction on the dimensional relationship of each part. You get what you design.

[0014]

As is apparent from the above description, according to the present invention, the polarization of all the piezoelectric elements of the main vibration system and the switching system is performed in the same polarity. You can get things. According to another aspect of the present invention, in addition to the above, a notch is provided on the outer peripheral portion of the extension line of the driver line, so that the rotation of the rotor can be smoothly switched while ensuring the displacement of the node line.

[Brief description of the drawings]

FIG. 1 is a top view of a main part according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating the operation of the first embodiment of the present invention.

FIG. 3 is an equivalent circuit diagram of the first embodiment of the present invention.

FIG. 4 is a top view of a main part of a conventional ultrasonic motor.

[Explanation of symbols]

 1 Substrate 2a, 2b First piezoelectric element 3a, 3b Second piezoelectric element 4a, 4b Driver 5a, 5b Notch

Claims (2)

[Claims] An even number of first piezoelectric elements of a main vibration system and a second piezoelectric element of a switching system corresponding to each of the first piezoelectric elements are alternately arranged so as to be circular, annular, and cylindrical. And the polarization directions of the first and second piezoelectric elements are all the same, and they are respectively connected in parallel to a pair of the first piezoelectric elements which are located at the center symmetrical position and connected in series to each other. The second piezoelectric element is switched to selectively displace a main vibration node line to one of both sides of a driver disposed at a central position of the second piezoelectric element and to which a rotor is engaged. Ultrasonic motor. 2. The ultrasonic motor according to claim 1, wherein a notch for facilitating displacement of the node line is provided in an outer peripheral portion of the extension line of the driver arrangement line.