JP2001268950A - Ultrasonic motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic motor that can prevent an increase of cost and also can realize improvement of output and reduction in size. SOLUTION: This ultrasonic motor comprises a disc type or polygon type elastic member, a vibrator formed by joining a piezoelectric element or an electrostrictive element to the elastic member and a rotor that is placed with pressure in contact with a driver provided to the vibrator. In this structure, the vibrator having a stepped portion is formed at the area near the nodal circle position of the vibration wave generated when an electric signal in the ultrasonic wave region is applied to the piezoelectric element or electrostrictive element of the vibrator.

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 that rotates by applying an electric signal in an ultrasonic range to a piezoelectric element. The present invention relates to an ultrasonic motor for transmitting to a motor.

[0002]

2. Description of the Related Art As a type of ultrasonic motor, there is generally known a so-called standing wave system in which a standing wave of thickness bending vibration is generated in a vibrator. And 2 corresponding to each one of the first piezoelectric elements of the main vibration system.
By configuring a second piezoelectric element of the direction switching system arranged one by one, by selecting the energization of the second piezoelectric element,
An ultrasonic motor that moves the node diameter of the vibration and changes the movement of the driver to change the rotation direction of the rotor (Japanese Patent Application No. 8-11 / 1996)
5210, Japanese Patent Application No. 9-56815).
Hereinafter, the related art will be described with reference to FIG. FIG.
FIG. 3A is a conceptual diagram of a conventional standing wave ultrasonic motor, and FIG. 3B is a perspective view of the vibrator of FIG. 3A as viewed from the piezoelectric element side. c) is B1 in FIG.
The operation waveform diagram in the section of -B2 is shown.

In FIG. 3A, reference numeral 1 denotes a disc-shaped elastic body, 2 denotes a piezoelectric element, 3 denotes a vibrator formed by joining the piezoelectric element 2 to the elastic body 1, and 4a and 4b denote vibrators on the vibrator 3. , 5 denotes a friction material, and 6 denotes a rotor which is an output shaft having the friction material. The rotor 6 is in pressure contact with the drivers 4 a and 4 b of the vibrator 3 via the friction material 5.

In FIG. 3B, a piezoelectric element 2 includes a main vibration system piezoelectric element 7a, 7b and a direction switching system piezoelectric element 8a, which is provided corresponding to the main vibration system piezoelectric element.
8b, 9a and 9b.

Next, the operation of the standing wave type ultrasonic motor will be described. Now, the piezoelectric element 7a of the main vibration system,
When bending resonance occurs between the piezoelectric element 7b and the second piezoelectric elements 8a and 8b of the direction switching system, as shown in FIG. 3B, a nodal diameter of vibration is formed on the line A1-A2 on the areas 9a and 9b where current is not supplied. . FIG. 3C shows the movement when the driver 4a is bent toward the rotor during this time. That is, the driver 4a
Is △ in the vertical direction due to the positional relationship with the nodal diameters A1-A2.
y, △ x is displaced simultaneously in the horizontal direction. Therefore, the driver 4
The rotor 6 which is in contact with a receives a rightward force in FIG. 3C and rotates left as viewed in FIG. 3B. Also, at this time, the other driver 4b is in a posture away from the rotor, and in the next half cycle, the driver 4b works and the driver 4a rests, thus rotating the rotor alternately.

Next, in order to perform reverse rotation, the piezoelectric elements 7a and 7b of the main vibration system and the second piezoelectric elements 9a and 9b of the direction switching system are used.
Since the nodal diameters occur on 8a and 8b, the driver 4a in FIG. 3C has the opposite inclination and moves away from the rotor, so that clockwise rotation is achieved. The same applies to the driver 4b. As described above, the rotation of the rotor can be performed by the piezoelectric element of the direction switching system.

[0007]

In the conventional ultrasonic motor described above, as a method for improving the output torque, the size of the vibrator and the piezoelectric element is increased and the plate of the vibrator and the piezoelectric element is increased. A method for adjusting the thickness to an optimum thickness is known. Further, as another method, in principle, a method of increasing the number of even-numbered drivers arranged on the vibrator, that is, a method of increasing the number of node diameters of the vibration can be considered. However, these methods of increasing the size of the vibrator and the piezoelectric element and increasing the plate thickness have a problem that the size and cost are increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an ultrasonic motor capable of preventing an increase in cost, improving output, and reducing the size. is there.

[0009]

In order to solve the above problems, a piezoelectric element or an electrostrictive element is joined to a vibrator made of a disc-shaped or polygonal elastic body, and the piezoelectric element or the electro-strictive element is joined. This is a means for solving the problem by forming a vibrator having a stepped portion near a nodal position of a vibration wave generated in the vibrator when an electric signal in an ultrasonic region is applied to the distortion element.

That is, the ultrasonic motor according to the present invention comprises a vibrator 3 having a disc-shaped or polygonal elastic body 1 and a piezoelectric element 2 or an electrostrictive element joined to the elastic body 1.
And an ultrasonic motor having a rotor 6 pressed and pressed against a driver 4 disposed on the vibrator 3, wherein the piezoelectric element 2 or the electrostrictive element of the vibrator 3 has an ultrasonic region. A vibrator 3 having a stepped portion 10 is formed near a nodal position of a vibration wave generated when an electric signal is applied.

[0011]

According to the present invention, the vibrator 3 having the stepped portion 10 is formed in the vicinity of the nodal circle position of the vibration wave generated in the vibrator 3, and the driver 4 disposed on the vibrator 3 is provided. Is rotated in response to the bending vibration of the vibrator 3.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A shows an embodiment of the present invention, and FIG. 1B shows a perspective view of the vibrator of FIG. 1A as viewed from the piezoelectric element side. In FIG. 1A, reference numeral 1 denotes a disc-shaped elastic body having a stepped portion 10;
Is a vibrator formed by joining the piezoelectric element 2 to the elastic body 1. 4 is a driver provided on the vibrator 3, 5 is a friction material,
Reference numeral 6 denotes a rotor which is an output shaft having the friction material. The rotor 6 is in pressurized contact with the driver 4 of the vibrator 3 and rotates by the vibration generated by the vibrator. The principle of this rotation operation is the same as that of the prior art, so that the description is omitted.

Here, the shape of the vibrator 3 of the present invention will be specifically described. The vibrator 3 of the present invention has a shape having a stepped portion 10 in the vicinity of a nodal circle position 11 of a vibration wave generated when a voltage in an ultrasonic region is applied to the piezoelectric element 2. Therefore, compared with the case where the stepped portion 10 is not provided, the stepped portion 10 is more likely to generate the bending vibration of the vibrator 3, so that the generation of the vibration wave is large. Accordingly, the vibration displacement becomes large, so that the output can be improved.

Hereinafter, the results of evaluation of the vibrator having the stepped portion of the present invention will be described. A striking difference was observed between the vibrator having the step portion of the present embodiment and the vibrator not performing the present embodiment, and the superiority of the vibrator having the step portion of the present embodiment was confirmed.

FIG. 2 is a sectional view showing a second embodiment of the ultrasonic motor according to the present invention. In the present invention, the shape of the vibrator 3 having the stepped portion 10 in FIG. 1 from the vicinity of the nodal circle position 11 to the outer peripheral portion is tapered, and the object is as in the first embodiment of the present invention. Is the same. Although not particularly shown, the tapered portion may have a shape in which the plate thickness from the stepped portion to the outer peripheral portion gradually increases.

FIG. 1B shows a case where the piezoelectric element 2 is divided into two parts, and the present invention can be applied to even divisions such as four divisions, six divisions, and eight divisions. Further, in FIG.
The polarization direction of the piezoelectric element 2 is divided into + and-, but a series connection in which all areas are set to the same direction may be used.

[0017]

As described above, according to the present invention, a practical effect that the output can be improved only by forming a shape having a step portion near the nodal circle position of the vibration wave generated in the vibrator is achieved. Is a great thing. Further, according to the present invention, since the stepped portion is provided at the position where the nodal circle of the vibration wave generated in the vibrator is generated, the vibrating wave has an effect of regulating the nodal circle position of the vibration.
Further, according to the present invention, since the vibrator may have a shape having a stepped portion, not only the weight can be reduced, but also the cost can be reduced.

[Brief description of the drawings]

FIG. 1 shows a first embodiment of an ultrasonic motor according to the present invention,
(A) is a sectional view thereof, and (b) is a perspective view seen from a piezoelectric element side.

FIG. 2 is a sectional view showing a second embodiment of the ultrasonic motor according to the present invention.

FIG. 3 shows a conceptual diagram of a conventional ultrasonic motor, and FIG.
Is a cross-sectional view thereof, and (b) and (c) are schematic views for explaining the operation.

[Explanation of symbols]

1 elastic body, 2 piezoelectric element, 3 vibrator,
4, 4a, 4b driver, 5 lining material, 6 rotor, 7a, 7b piezoelectric element of main vibration system, 8a, 8b, 9a, 9b piezoelectric element of direction switching system, 10 stepped portion, 11 node circle position

Claims (1)

[Claims] 1. An elastic body having one of a disk shape and a polygonal shape,
An ultrasonic motor comprising: a vibrator formed by joining a piezoelectric element or an electrostrictive element to the elastic body; and a rotor that is pressurized and pressed against a driver disposed on the vibrator. An ultrasonic motor characterized in that a vibrator having a stepped portion is formed near a nodal circle position of a vibration wave generated when an electric signal in an ultrasonic region is applied to the piezoelectric element or the electrostrictive element.