JPH02303377A - ultrasonic motor - Google Patents

Abstract

PURPOSE:To suppress fluctuation of rotation and torque by providing a projection for receiving pressurizing force on a mover. CONSTITUTION:An ultrasonic motor comprises a housing 1, a stator 6 having a piezoelectric element, a rotary shaft 20, a mover 24 secured thereto, a belleville spring 30, and the like. An annular projection 25 for receiving the pressure functioning section 30a of the belleville spring 30 is formed integrally on the upper face of the mover 24, and the pressurizing force of the belleville spring 30 is distributed uniformly in the circumferential direction through a spring receiving section 25a notched in the annular projection 25. By such arrangement, noise can be suppressed and high output can be produced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an ultrasonic wave generator configured to press a movable element against a stator by a spring means and drive the movable element by an elastic traveling wave generated in the stator. The present invention relates to a motor, and specifically relates to the structure of a joint between a spring means and a movable element.

[Prior art] As a conventional ultrasonic motor of this type, there is a
One example is the technology published in Publication No. 887.

FIG. 3 is a vertical sectional view showing a conventional ultrasonic motor, FIG. 4 is a partial sectional view showing an enlarged contact area between the stator and the movable element in the ultrasonic motor shown in FIG. 3, and FIG. FIG. 4 is an explanatory diagram showing the distribution state of the pressing force of the disc spring used in the ultrasonic motor of FIG. 4;

In FIG. 3, 41 is a case that forms the outer shell of the ultrasonic motor, 42 is a cover that closes the case 41, 43 is a stator,
44 is a piezoelectric element disposed on the stator 43, 45 is a movable element arranged to be joined to the stator 43 via a liner 46, and 47 is a rotating shaft that rotates together with the movable element 45. A disc spring 50 that presses against the thin wall portion 49 of the movable element 45 is disposed below the large-diameter flange portion 48 of the rotating shaft 47 . Also, a snap ring 5 is provided at the bottom of the rotating shaft 47.
1 holds a shim 52, and by selecting the thickness of this shim 52, the pressing force of the disc spring 50 can be adjusted as appropriate.

In the conventional ultrasonic motor configured as above,
When a high frequency voltage is applied to the piezoelectric element 44, the piezoelectric element 4
Along with the deformation of the stator 4, an elastic traveling wave is generated in the stator 43, and this elastic traveling wave causes an elliptic motion in the mass point on the surface of the stator 43. Along with this elliptical movement, the stator 4
3 and the liner 46 fixed to the movable element 45, a frictional force is generated on the contact surface between the liner 46 fixed to the movable element 45, a rotational moment acts on the movable element 45 by the frictional force, and the rotary shaft 47 is rotated together with the movable element 45. .

[Problems to be Solved by the Invention] By the way, the output of this type of ultrasonic motor 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. are respectively bent, and the stator 43 and the liner 46 fixed to the movable element 45 are pressed against each other in a one-sided state. Also, disc spring 50
Due to its own spring characteristics, the pressing force in the circumferential direction is uneven as shown by the arrows in Fig. 5, so the movable element 45 is pressed against the stator 43 with uniform force at each part. It is difficult to do so.

Therefore, it is expected that the fluctuation range of the friction coefficient and pressure contact force between the stator 43 and the liner 46 fixed to the movable element 45 will increase, causing uneven rotation or torque, resulting in unstable motor output. . Moreover, in a state where the friction coefficient and the pressure contact force are unstable, a natural vibration of a frequency different from that of the stator 43 is generated in the movable element 45, which may cause an inconvenience that abnormal noise is generated. And for these reasons,
Up until now, it has been difficult to increase the output of ultrasonic motors.

Therefore, an object of the present invention is to uniformly distribute the pressing force of the spring means in the circumferential direction of the movable element with a simple structure, to suppress rotational unevenness, torque unevenness, and generation of abnormal noise, thereby achieving high output. Our goal is to provide an ultrasonic motor that can achieve

[Means for Solving the Problems] An ultrasonic motor according to the present invention includes a movable element that is arranged to come into elastic contact with a stator that generates an elastic traveling wave by deformation of a piezoelectric element and is driven by the elastic traveling wave; It is comprised of a spring means for pressurizing the movable element toward the stator, and a protrusion disposed on the movable element so as to receive the pressing force of the spring means.

[Operation] In the ultrasonic motor of the present invention, since the movable element is provided with a protrusion that receives the pressing force of the spring means, the pressing force of the spring means is uniformly distributed on the movable element along the protrusion. . In addition, since the movable element is reinforced by projections at the portion that engages with the pressing force of the spring means, there is no risk of the movable element being bent by the pressing force of the spring means, and the stator and the movable element are always in stable contact. Pressure is applied through the surface. Therefore, the friction coefficient and pressure contact force of the liner fixed to the stator and mover are stabilized, rotational unevenness and torque unevenness are suppressed, and the natural vibration of the mover is suppressed, thereby preventing the occurrence of abnormal noise. Ru. As a result, high power can be supplied to the piezoelectric element and high motor output can be obtained without any problem.

[Embodiments] Hereinafter, embodiments embodying the present invention will be described based on 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 movable element installed in the ultrasonic motor of FIG.

The housing 1 of the ultrasonic motor of this embodiment is composed of a base 2 and a cover 3 that covers the top of the base 2. A support cylinder 4 is formed in the center of the base 2 and projects inward. A bearing 1 is installed in the support tube 4.
7 is press-fitted, and movement inward is restricted by the overhanging portion 5 of the support tube 4. Inner ring 17a of the bearing 17
A rotating shaft 20 is inserted from below. Said rotating wheel 2
0 includes an output portion 21 that projects downward from the housing 1, a collar portion 22 that contacts the lower surface of the bearing 17, and a connecting portion 23 at the upper end, and the housing 1 is moved inward by the collar portion 22. is regulated.

The holder 18 is inserted into the connecting portion 23 of the rotating shaft 20 so as to be relatively unrotatable via a rotation preventing means such as a surface joint or a spline joint. A shim 34 is interposed between the holder 18 and the bearing 17. Then, by housing the washer 15 in the upper recess 18a of the holder 18 and tightening the screw 19 to the upper end of the rotating shaft 20, the holder 18 is prevented from being removed by the washer 15, and the shim 3
4 is clamped, and in that state, the rotating shaft 20 and the bearing 1
The inner ring 17a1 holder 18 of No. 7 and the shim 34 are each connected to be rotatable together.

The inner hole 7 of the stator 6 is inserted into the outer periphery of the support cylinder 4 of the base 2 . The stator 6 is integrally constructed of a small-diameter ring portion 8, a large-diameter ring portion 9, and a thin-walled portion 10 of an elastic metal material such as phosphor bronze. The small-diameter ring portion 8 is fixed to the support tube 11 of the base 2 by screws 12 while being joined to the support tube 11 . A large number of comb teeth 13 are protruded from the upper surface of the large diameter ring portion 9 at a constant pitch over the entire circumference.

A piezoelectric element 14 formed into 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 circuit board 31 and a printed circuit board 32 disposed at an end thereof. When high-frequency power is applied to the piezoelectric element 14, an elastic traveling wave, that is, an ultrasonic vibration, is generated in the large diameter ring portion 9 of the stator 6 as the piezoelectric element 14 expands and contracts.

The holder 1 is connected to the stator 6 from above.
A movable member 24 is inserted into the movable member 8 through a rotation preventing means such as a surface joint or a spline joint so as to be relatively unrotatable. The movable element 24 is formed into a disk shape from a metal material such as aluminum, and has a ring-shaped protrusion 26 projecting downward from its outer periphery. The lower surface of the ring-shaped convex portion 26 is in contact with <[13] of the stator 6 via the liner 28.

A disc spring 30 serving as a spring means for pressurizing the movable element 24 toward the stator 6 is inserted into the holder 18 above the movable element 24, and is pressed and held from above by the flange 18b of the holder 18 at one end. ing.

Further, an annular projection 25 is integrally formed on the upper part of the movable element 24 at a position corresponding to the outer peripheral edge of the disc spring 30. On the inner periphery of the annular projection 25, there is a spring bearing portion 2 that receives the outer periphery of the disc spring 30, that is, the pressure acting portion 30a.
5a is cut out. A rubber ring 2 as an elastic member is provided between the spring bearing portion 25a and the pressure acting portion 30a.
7 is interposed. Note that the pressing force of the disc spring 30 is adjusted as appropriate by changing the thickness of the shim 34.

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

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. This 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 expanded by the comb teeth 13 of the large-diameter ring portion 9.

Then, an elliptical motion is generated in the mass points on the surface of the comb teeth 13, and along with this elliptical motion, a frictional force is generated on the contact surface between the stator 6 and the liner 28 fixed to the movable element 24.

This frictional force causes a rotational moment to act on the movable element 24, thereby causing the movable element 24, the holder 18, and the rotating shaft 20 to rotate together.

As described above, in the ultrasonic motor of this embodiment, the annular protrusion 25 that receives the pressurizing portion 30a of the disc spring 30 is integrally formed on the upper surface of the movable element 24, so that the pressurizing force of the 1111 spring 30 is reduced. The movable element 24 along the annular protrusion 25
uniformly distributed in the circumferential direction.

Furthermore, since the movable element 24 is reinforced by the annular protrusion 25 at the portion that engages with the pressurizing portion 30a of the disc spring 30, there is no possibility that the movable element 24 will curve due to the pressing force of the disc spring 30, and the stator 6 and the movable element 24 are always pressed together through a stable contact surface.

Therefore, the friction coefficient and pressure contact force between the liner 28 fixed to the movable element 24 and the stator 6 are stabilized, and uneven rotation and torque are suppressed. In addition, when the liner 28 fixed to the movable element 24 and the stator 6 are in stable pressure contact, the natural vibration of the frequency different from that of the stator 6 is less likely to occur in the movable element 24, and the movable element 24 and the disc spring 30 etc., the generation of abnormal noise is prevented. As a result, high power can be supplied to the piezoelectric element 14 and high motor output can be obtained without any problem.

Moreover, since the annular protrusion 25 is integrally fixed to the movable element 24, the number of parts is reduced compared to the case where separate parts are interposed between the movable element 24 and the disc spring 30, making it lightweight and easy to assemble. With a structure that is easy to attach, the pressing force of the disc spring 30 can be stabilized. Furthermore, in this example,
Since the rubber ring 27 as an elastic member is interposed between the annular protrusion 25 and the disc spring 30, the vibration of the movable element 24 is less likely to be transmitted to the 1111 spring 30 side, and damping of vibration energy can be suppressed. .

In the above embodiment, the annular protrusion 25 is integrally formed with the movable member 24, but the present invention is not limited to this, and the annular protrusion 25 and the movable member 24 may be separated. They can also be assembled after being formed and fixed together in advance with a fixing means such as adhesive or welding.

Alternatively, the annular projections 25 can also be used as projections arranged at a predetermined pitch. However, according to this embodiment in which the annular protrusion 25 is integrally formed with the movable element 24,
The precision of the annular protrusion 25 is improved, and the unique effect that the pressing force of the disc spring 30 can be uniformly distributed in the circumferential direction of the movable element 24 can be obtained.

Furthermore, although the ultrasonic motor of this embodiment is configured so that the movable element 24 performs rotational motion, the present invention can be applied to a linear type ultrasonic motor in which the movable element is configured to perform linear motion. It is also possible to convert Of course, in this case, the annular projections 25 of the above embodiment may be linear projections or projections 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 elastic traveling waves using piezoelectric elements, and an elastic traveling wave that is arranged so as to be in elastic contact with the stator. It is extremely simple because it consists of a movable element that is moved toward the stator, a spring means that presses the movable element toward the stator, and a protrusion that is arranged on the movable element so as to receive the pressing force of the spring means. With this structure, the pressing force of the spring means can be uniformly distributed in the circumferential direction of the movable element, and rotational unevenness, torque unevenness, and generation of abnormal noise can be suppressed, thereby making it possible to obtain high output.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of an ultrasonic motor according to an embodiment of the present invention, FIG. 2 is a perspective view showing a movable element installed in the ultrasonic motor of FIG. 1, and FIG. 3 is a conventional ultrasonic motor. FIG. 4 is a partial sectional view showing an enlarged view of the contact area between the stator and the movable element in the ultrasonic motor shown in FIG. 3, and FIG. FIG. 3 is an explanatory diagram showing the distribution state of the pressing force of the 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 the same symbols indicate the same or equivalent parts. Patent applicant: 1 person other than Aisin Seiki Co., Ltd.

Claims (3)

[Claims] (1) A stator that generates an elastic traveling wave using a piezoelectric element, a movable element that is arranged to come into elastic contact with the stator and is driven by the elastic traveling wave, and a movable element that is directed toward the stator. An ultrasonic motor comprising: a pressurizing spring means; and a projection disposed on the movable member so as to receive the pressurizing force of the spring means. (2) The ultrasonic motor according to claim 1, wherein the projection is an annular projection formed integrally with the movable element. (3) The ultrasonic motor according to claim 1 or 2, wherein an elastic member is interposed between the annular projection and the spring means.