JP2980712B2 - Ultrasonic motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor formed to rotate a rotor using ultrasonic vibration.

[0002]

2. Description of the Related Art In a conventional ultrasonic motor, a rotor is brought into contact with an upper surface of a cylindrical stator, and a piezoelectric element that performs torsional vibration in the circumferential direction on the stator and longitudinal vibration in an axial direction. By forming a piezoelectric element and combining torsional vibration and longitudinal vibration, the upper surface of the stator is moved to draw a Lissajous figure, and the rotor that is in contact with the upper surface is formed to rotate. I have.

[0003]

However, in the conventional ultrasonic motor, it is necessary to excite both the piezoelectric elements so that the frequency of the torsional vibration and the frequency of the longitudinal vibration coincide with each other. Therefore, high precision is required, an expensive control device is required, and two piezoelectric elements are required, so that the structure is complicated and the cost is high.

[0004] The present invention has been made in view of these points, the rotor can be rotated by only one type of ultrasonic vibration source, the rotation is smooth, the output torque is large, the control of the rotation operation is easy. It is an object of the present invention to provide an ultrasonic motor having a simple structure and a low cost.

[0005]

In order to achieve the above object, an ultrasonic motor according to the present invention comprises a stator having a vibration applying surface capable of vibrating in a normal direction thereof, and a vibrating means for applying vibration to the stator. Means, and a rotor abutting on the vibration applying surface via a driving force converting means, wherein the driving force converting means converts the vibration received from the vibration applying surface into a driving force for rotating the rotor. in the ultrasonic motor is formed by the conversion element, wherein the vibrating means is a stearyl
A pair of electrodes facing each other
At least one electrode corresponding to the center of the rotor
Min has been removed, the formed so as to vibrate by less than the displacement speed of the outer circumferential portion of the displacement speed at the center of the rotor of the vibration applying surface, wherein the conversion element before
It is characterized by being present over a predetermined range in the radial direction of the rotor .

[0006]

According to the ultrasonic motor of the present invention, when the stator is vibrated by the vibrating means, the vibration received from the vibration applying surface of the stator by the converting element as the driving force converting means is converted into the driving force for rotating the rotor. Convert, the rotor rotates. Then, in order for the vibration means to vibrate while making the displacement speed at the center of the rotor of the vibration applying surface smaller than the displacement speed at the outer peripheral portion, the rotational force received by the conversion element from the vibration applying surface is In accordance with the displacement speed, the rotor has an appropriate size in the radial direction such that the center portion of the rotor is small and the outer peripheral portion is large, so that the rotor rotates smoothly and the output torque is large.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIGS. 1 and 2 show the principle of operation of the ultrasonic motor of the present invention.

In the drawing, reference numeral 1 denotes a base body, the upper surface 1a of which is a vibration applying surface, and the upper surface 1a is formed so as to vibrate vertically by a vibration mechanism (not shown).

On a top surface 1a of the base body 1, a rotating body 2 formed in a disk or column shape is mounted with a plurality of blades 3, 3,...

Each blade 3 is perpendicular to the lower surface of the rotating body 2, that is, normal to the upper surface 1 a of the base body 1.
The upper surface 1a is fixed by being inclined by the angle θ, and separates external force received from the vertical vibration of the upper surface 1a to form an upper surface 1a.
A component component directed in the tangential direction of a is extracted and converted into a driving force for rotating the rotating body 2. Are fixed to the position of the concentric circle O from the center of the rotating body 2 so that the driving force is directed in the same tangential direction of the concentric circle O.

Next, the operation principle of the moving body will be described.

When rotating the rotating body 2, the upper surface 1a of the base body 1 is vibrated up and down by a vibrating mechanism. Each of the blades 3 of the rotating body 2 that has received the vertical vibration of the upper surface 1a is driven by the external force received from the vibration to move the moving body 2 in the horizontal direction, that is, the driving force of the concentric circle O in the same tangential direction. , The rotating body 2 is rotated by these driving forces.

However, since each blade 3 is disposed with its lower end face directed in the radial direction, the rotational force generated in each blade 3 is the same in the radial direction. It is presumed that the rotational force becomes excessive and slippage occurs with the upper surface 1a.

The ultrasonic motor according to the present invention is formed so that such a slip does not occur and the rotor rotates smoothly.

FIGS. 3 and 4 show an embodiment of the ultrasonic motor of the present invention to which the principle shown in FIGS. 1 and 2 is applied.

The ultrasonic motor according to this embodiment has a stator 11
Is formed in a cylindrical shape by the piezoelectric element 12 serving as a vibrating means. The piezoelectric element 12 causes the stator 11 to vibrate in the axial direction by ultrasonic waves. Electrodes 12a and 12b for energization are fixed to upper and lower surfaces, respectively. In this embodiment, the electrode 12a fixed to the upper surface is formed in an annular shape with the central portion removed. As a result, the piezoelectric element 12 is energized only in the outer peripheral portion excluding the central portion, which causes a difference in the Young's modulus for the axial deflection of the piezoelectric element 12 between the central portion and the outer peripheral portion. Is generated, and the axial displacement speed of the central portion is suppressed to be lower than the displacement speed of the outer peripheral portion. The electrode 12a on this
The upper surface 11a of the stator 11 provided with is a vibration applying surface. The rotor 13 mounted on the upper surface 11a of the stator 11 is formed in substantially the same manner as the moving body 2 shown in FIGS. That is, on the lower surface of the rotor 13, a plurality of blades 14, 14,... Serving as conversion elements of driving force conversion means for converting vibration of the upper surface 11a into driving force in the rotational direction.
Are arranged concentrically around the center of the rotor 13.

Next, the operation of this embodiment will be described.

According to the ultrasonic motor of this embodiment, the electrode 1
When the piezoelectric element 12 is energized and excited through 2a and 12b, and the upper surface 11a of the stator 11 is ultrasonically vibrated,
Each blade 14 fixed to the lower surface of the rotor 13 applies ultrasonic vibration in the tangential direction of the upper surface 11a, and
Are taken out as driving forces directed in the same tangential direction of concentric circles around the rotation center of
3 rotates coaxially with the stator 11.

At this time, in this embodiment, the piezoelectric element 1
Since the central portion of the electrode 12a provided on the upper surface of the piezoelectric element 12 is removed, the piezoelectric element 12 is energized only to the outer peripheral portion excluding the central portion, and the Young's modulus of the piezoelectric element 12 with respect to the axial deflection of the piezoelectric element 12 is reduced. A difference occurs between the values of the central portion and the outer peripheral portion, and as shown in FIG. 5, the displacement speed in the axial direction of the central portion can be suppressed to be smaller than the displacement speed of the outer peripheral portion. Therefore, the rotational force generated in each blade 14 is small in the central portion of the rotor 13 and large in the outer peripheral portion in accordance with the displacement speed of the upper surface 11a of the stator 11, which is the vibration imparting surface, and has an appropriate size in the radial direction. Slip between the blades 14 and the upper surface 11a is extremely small, the rotor 13 rotates smoothly, and the output torque is large.

In order to suppress the displacement speed of the central portion of the piezoelectric element 12, at least one of the central portions of the pair of electrodes 12a and 12b may be removed.

The ultrasonic motor according to this embodiment has a stator 11
The rotor 13 can be rotated only by causing the piezoelectric element 12 to ultrasonically vibrate, the rotation is smooth, the output torque is large, and the configuration is simple.
The whole structure can be formed small. Therefore, it can be used in various industrial fields where the appearance of small motors is desired. For example, it can be provided at the tip of a fiberscope, which is a kind of medical equipment, and can be used as a drive source for various small medical scalpels such as a laser scalpel. Further, since the configuration is simple, the number of failures is small and the cost can be reduced.

In the embodiment shown in FIGS. 3 to 5, the rotors 13 are respectively mounted on the upper surface 11a of the stator 11 serving as upward vibration imparting surfaces by their own weights so that the rotors 13 are always in contact with each other. However, a constant contact force may be applied to the rotor 13 using a suitable spring or the like other than the own weight. Further, the rotor 13 may be brought into contact with the stator 11 by magnetic force. In this case, the rotor 13 can be moved by bringing the rotor 13 into contact with the vibration applying surface even if the vibration applying surface is not limited to the horizontal plane and is a vertical surface or a downward surface. In particular, this case is extremely suitable for a case of rotational driving in a weightless field such as the outer space.

Further, in each of the above-described embodiments, the blade 14 is used as the driving force converting means. However, the present invention is not limited to the blade, and any structure may be used as long as it can convert vibration into driving force. Good.

It should be noted that the present invention is not limited to the above-described embodiment, and can be changed as needed.

[0026]

As described above, since the ultrasonic motor of the present invention is constructed and operates, the rotor can be rotated only by one kind of ultrasonic vibration source, the rotation is smooth and the output torque is large, The control of the rotation operation is facilitated, the structure is simple, and the cost is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing the principle of rotation of an ultrasonic motor according to the present invention.

FIG. 2 is a perspective view of the lower surface side of the rotating body of FIG. 1;

FIG. 3 is a sectional view showing an embodiment of the ultrasonic motor according to the present invention.

FIG. 4 is an exploded perspective view of FIG. 3;

FIG. 5 is a diagram showing a displacement speed characteristic of a rotor in a radial direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Stator 11a Upper surface 12 Piezoelectric element 12a, 12b Electrode 13 Rotor 14 Blade

Claims (1)

(57) [Claims] 1. A stator having a vibration applying surface capable of vibrating in a normal direction thereof, vibrating means for applying vibration to the stator, and a rotor abutting on the vibration applying surface via driving force converting means. Wherein the driving force converting means is an ultrasonic motor formed by a converting element for converting vibration received from the vibration applying surface into driving force for rotating the rotor, wherein the vibrating means includes the stator. Vs through
And a pair of electrodes facing each other.
The portion of the electrode corresponding to the center of the rotor is removed
Cage, wherein is formed so as to vibrate by less than the displacement speed of the outer circumferential portion of the displacement speed at the center of the rotor of the vibration applying surface, wherein the conversion element of the rotor radial direction
An ultrasonic motor, wherein the ultrasonic motor is provided over a predetermined range of directions .