JP2810109B2 - Ultrasonic motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention presses a mover to a stator by spring means,
The present invention relates to an ultrasonic motor configured to drive a mover by an elastic traveling wave generated in the stator, and more particularly, to a structure of a joint between a spring means and a mover.

[Prior Art] A conventional ultrasonic motor of this type is disclosed in JP-A-63-7388.
The technology described in Japanese Patent Publication No. 7 is cited.

FIG. 3 is a longitudinal sectional view showing a conventional ultrasonic motor, FIG. 4 is an enlarged partial sectional view showing a contact portion between a stator and a mover in the ultrasonic motor shown in FIG. 3, and FIG. FIG. 5 is an explanatory diagram showing a distribution state of a pressing force of a disc spring used in the ultrasonic motor of FIG. 4.

In FIG. 3, reference numeral 41 denotes a case serving as an outer shell of the ultrasonic motor, reference numeral 42 denotes a cover for closing the case 41, reference numeral 43 denotes a stator, reference numeral 44 denotes a piezoelectric element provided on the stator 43, and reference numeral 45 denotes a liner 46 A mover 47 that is arranged to be joined to the stator 43 is a rotating shaft that rotates integrally with the mover 45. The rotary shaft 47
Below the large-diameter flange portion 48, a disc spring 50 that presses the thin portion 49 of the mover 45 is disposed. In addition, a shim 52 is held by a snap ring 51 at a lower portion of the rotating shaft 47,
By selecting the thickness of the shim 52, the pressing force of the disc spring 50 can be appropriately adjusted.

In the conventional ultrasonic motor configured as described above, when a high-frequency voltage is applied to the piezoelectric element 44, the piezoelectric element
An elastic traveling wave is generated in the stator 43 along with the deformation of 44, and the elastic traveling wave causes an elliptical motion to occur at a mass point on the surface of the stator 43. Then, a frictional force is generated on the contact surface between the stator 43 and the liner 46 fixed to the mover 45 due to the elliptical motion, and a rotational moment acts on the mover 45 by the frictional force. The rotation shaft 47 is integrally rotated.

[Problems to be Solved by the Invention] The output of this type of ultrasonic motor is generally
It depends on the friction coefficient between the stator 43 and the liner 46 and the pressing force of the disc spring 50. However, when the pressing force of the disc spring 50 is set to be large in the conventional ultrasonic motor, as shown in an enlarged view in FIG.
And the thin portion 54 of the stator 43 is curved, respectively,
43 and the liner 46 fixed to the mover 45 are pressed against each other in a one-sided state. Further, since the disc spring 50 has a nonuniform pressing force in the circumferential direction as shown by an arrow in FIG. It is difficult to pressurize with great force.

Therefore, it is expected that the fluctuation range of the friction coefficient and the pressing force between the stator 43 and the liner 46 fixed to the mover 45 becomes large, and uneven rotation or torque occurs, and the motor output becomes unstable. . In addition, in a state where the friction coefficient and the pressing force are unstable, a natural vibration of a frequency different from that of the stator 43 is generated in the mover 45, which may cause an inconvenience that abnormal noise is generated. For these reasons, conventionally, high output of the ultrasonic motor has been hindered.

Therefore, an object of the present invention is to distribute the pressing force of the spring means evenly in the circumferential direction of the mover with a simple structure, thereby suppressing the occurrence of uneven rotation and uneven torque, and the occurrence of abnormal noise, thereby achieving high output. To provide an ultrasonic motor capable of obtaining the following.

[Means for Solving the Problems] An ultrasonic motor according to the present invention includes: a movable element that is disposed so as to elastically contact a stator that generates an elastic traveling wave by deformation of a piezoelectric element and is driven by the elastic traveling wave; It comprises a spring means for pressing the mover in the direction of the stator, and a projection arranged on the mover to receive the pressing force of the spring means.

[Operation] In the ultrasonic motor of the present invention, since the projection receiving the pressing force of the spring means is provided on the movable element, the pressing force of the spring means is uniformly distributed on the movable element along the projection. . Further, since the mover is reinforced by the projection at a portion where the mover engages with the pressing force of the spring means, there is no possibility that the mover may be bent by the pressing force of the spring means, and the stator and the mover always have stable contact. Pressed through the surface. Therefore,
The coefficient of friction and the pressure contact force of the liner fixed to the stator and the mover are stabilized, and uneven rotation and torque are suppressed, and natural vibration of the mover is suppressed, thereby preventing generation of abnormal noise. As a result, high power can be supplied to the piezoelectric element, and a high motor output can be obtained without any trouble.

Examples Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view of an ultrasonic motor according to an embodiment of the present invention, and FIG. 2 is a perspective view showing a mover mounted on the ultrasonic motor of FIG.

The housing 1 of the ultrasonic motor of this embodiment has a base 2
And a cover 3 that covers the base 2 from above. A support cylinder 4 is formed at the center of the base 2 so as to protrude inward. The support cylinder 4 has a bearing
17 is press-fitted, and the inward movement is regulated by the overhang portion 5 of the support cylinder 4. The rotating shaft 20 is inserted into the inner ring 17a of the bearing 17 from below. The rotating shaft 20 includes an output portion 21 protruding downward from the housing 1, a flange portion 22 abutting on the lower surface of the bearing 17, and a connecting portion 23 at an upper end. Regulates movement to

The holder 18 is inserted into the connecting portion 23 of the rotating shaft 20 via a rotation preventing means such as surface joining or spline joining so as to be relatively non-rotatable. A shim 34 is interposed between the holder 18 and the bearing 17. Then, the washer 15 is accommodated in the upper recess 18a of the holder 18, and the screw 19 is fastened to the upper end of the rotating shaft 20, so that the holder 18 is prevented from coming off with the washer 15, and the shim 34 is clamped. In the state,
The rotating shaft 20, the inner ring 17a of the bearing 17, the holder 18, and the shim 34 are connected so as to be integrally rotatable.

The outer periphery of the support tube 4 of the base 2 has an inner hole 7 of the stator 6 inserted therein. The stator 6 has a small-diameter ring portion 8 and a large-diameter ring portion 9.
The thin portion 10 is integrally formed of a metal elastic material such as phosphor bronze. The small-diameter ring portion 8 is fixed by screws 12 in a state of being joined to the support surface 11 of the base 2. On the upper surface of the large-diameter ring portion 9, a large number of comb teeth 13 project at a constant pitch over the entire circumference.

A piezoelectric element 14 formed in a ring shape from a ceramic material or the like is fixed to the lower surface of the large-diameter ring portion 9 of the stator 6 via a conductive adhesive (not shown). The piezoelectric element 14 is connected to a connector 33 via a flexible printed board 31 and a printed board 32 provided at an end thereof. When high-frequency power is applied to the piezoelectric element 14, elastic traveling waves, that is, ultrasonic vibrations are generated in the large-diameter ring portion 9 of the stator 6 as the piezoelectric element 14 expands and contracts.

Holder so as to be joined to the stator 6 from above
A mover 24 is inserted into the member 18 via a rotation preventing means such as a surface joint or a spline joint so as to be relatively non-rotatable. The mover 24 is formed in a disk shape from a metal material such as aluminum, and a ring-shaped convex portion 26 is provided on an outer periphery thereof so as to protrude downward. The lower surface of the ring-shaped convex portion 26 is in contact with the comb teeth 13 of the stator 6 via the liner 28.

Above the mover 24, the holder 18
Spring 30 as a spring means for pressing the spring toward the stator 6
Is inserted and pressed and held from above by the upper end flange 18b of the holder 18.

An annular projection 25 is integrally formed on the upper surface of the mover 24 at a position corresponding to the outer peripheral edge of the disc spring 30. The inner periphery of the annular projection 25 is formed with a notch at the outer periphery of the disc spring 30, that is, a spring receiving portion 25a for receiving the pressurizing portion 30a. A rubber ring 27 as an elastic member is interposed between the spring receiving portion 25a and the pressing portion 30a.
The pressing force of the disc spring 30 is appropriately adjusted by changing the thickness of the shim 34.

Next, the operation of the ultrasonic motor of the present embodiment configured as described above will be described.

When high frequency power is applied to the piezoelectric element 14 fixed to the stator 6, the piezoelectric element 14 is distorted, and an elastic traveling wave is generated in the stator 6. The elastic traveling wave circulates along the large-diameter ring portion 9 of the stator 6, and in the process, the amplitude of the elastic traveling wave is enlarged by the comb teeth 13 of the large-diameter ring portion 9. Then, an elliptic motion is generated at the mass point on the surface of the comb tooth 13,
With this elliptical motion, a frictional force is generated on the contact surface between the stator 6 and the liner 28 fixed to the mover 24. Then, a rotational moment acts on the mover 24 due to this frictional force, whereby the mover 24, the holder 18, and the rotating shaft 20 are integrally rotated.

As described above, in the ultrasonic motor of the present embodiment, the annular projection 25 that receives the pressurizing portion 30a of the disc spring 30 is integrally formed on the upper surface of the mover 24, so that the pressing force of the disc spring 30 Along the annular protrusion 25, the movable member 24 is uniformly distributed in the circumferential direction. In addition, since the mover 24 is reinforced by the annular projection 25 at a portion of the disc spring 30 that engages with the pressurizing action portion 30a, there is no possibility that the mover 24 will be bent by the pressing force of the disc spring 30. 6 and the mover 24 are always pressed into contact with each other via a stable contact surface.

Therefore, the friction coefficient and the pressing force between the liner 28 fixed to the mover 24 and the stator 6 are stabilized, and the uneven rotation and the uneven torque are suppressed. Further, when the liner 28 and the stator 6 fixed to the mover 24 are stably pressed against each other, natural vibration of a frequency different from that of the stator 6 is less likely to occur on the mover 24, and the mover 24 and the disc spring Generation of abnormal noise at 30 mag is prevented. As a result, high power can be supplied to the piezoelectric element 14, and a high motor output can be obtained without any trouble.

Moreover, since the annular projection 25 is integrally fixed to the mover 24, the number of components is reduced as compared with a case where another component is interposed between the mover 24 and the disc spring 30, and the weight is reduced. With a structure that is easy to assemble, the pressing force of the disc spring 30 can be stabilized. Further, in the present embodiment, the annular projection
Since the rubber ring 27 as an elastic member is interposed between the disc spring 30 and the disc spring 30, the vibration of the mover 24 is not easily transmitted to the disc spring 30 side, and the attenuation of the vibration energy can be suppressed.

Although the annular projection 25 is formed integrally with the mover 24 in the above embodiment, the present invention is not limited to this, and the annular projection 25 and the movable element 24 may be divided. It is also possible to assemble them after forming them and fixing them together in advance with a fixing means such as an adhesive or welding. Alternatively, the annular projections 25 can be used as projections arranged at a predetermined pitch. However, according to the present embodiment in which the annular projection 25 is formed integrally with the mover 25, the annular projection 25
Of the disc spring 30 and the moving force of the mover 24
Has a specific effect that it can be uniformly distributed in the circumferential direction.

Further, the ultrasonic motor of the present embodiment is configured so that the mover 24 performs a rotational movement, but the present invention is applied to a linear ultrasonic motor configured so that the mover moves linearly. It is also possible to convert. Of course, in this case, the annular projection 25 of the above embodiment can be a linear projection or a projection arranged at a predetermined pitch.

[Effects of the Invention] As described in detail above, the ultrasonic motor of the present invention is driven by a stator that generates an elastic traveling wave by a piezoelectric element and an elastic traveling wave that is arranged to elastically contact the stator. The movable element is composed of a movable element, a spring means for pressing the movable element toward the stator, and a projection arranged on the movable element so as to receive the pressing force of the spring means. With such a structure, the pressing force of the spring means can be evenly distributed in the circumferential direction of the mover, so that uneven rotation and uneven torque and occurrence of abnormal noise can be suppressed, and thus a high output can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an ultrasonic motor according to one embodiment of the present invention, FIG. 2 is a perspective view showing a mover mounted on the ultrasonic motor of FIG. 1, and FIG. 3 is a conventional ultrasonic motor. FIG. 4 is an enlarged partial sectional view showing a contact portion between a stator and a mover in the ultrasonic motor of FIG. 3, and FIG. 5 is used in the ultrasonic motor of FIG. FIG. 4 is an explanatory diagram showing a distribution state of a pressing force of a coned disc spring. In the figure, 6: stator, 14: piezoelectric element, 24: mover, 25: annular projection, 30: disc spring. In the drawings, the same reference numerals and symbols indicate the same or corresponding parts.

Continued on the front page (72) Inventor Mutsuro Aoyama 2-1-1 Asahi-cho, Kariya-shi, Aichi Aisin Seiki Co., Ltd. (72) Inventor Shinji 3-105 Sugaya, Ageo-shi, Saitama Fukukoku (72) ) Inventor Tadayoshi Murakami 3-105 Sugaya, Ageo-shi, Saitama Fukuk Co., Ltd. (56) References JP-A-2-41677 (JP, A) JP-A 1-1110068 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H02N 2/00

Claims (3)

(57) [Claims] A stator configured to generate an elastic traveling wave by a piezoelectric element; a movable member arranged to be in elastic contact with the stator and driven by the elastic traveling wave; and the movable member attached to the stator. An ultrasonic motor comprising: spring means for applying pressure toward the movable member; and a projection disposed on the mover so as to receive a pressing force of the spring means. 2. The ultrasonic motor according to claim 1, wherein the projection is an annular projection formed integrally with the mover. 3. An ultrasonic motor according to claim 1, wherein an elastic member is interposed between said annular projection and said spring means.