JP3419962B2 - 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 used in cameras, optical equipment such as video movies, audio equipment such as CD players and the like.

[0002]

2. Description of the Related Art In recent years, ultrasonic motors have become highly reliable and miniaturized with the market expansion in optical equipment such as cameras and video movies, audio equipment such as CD players and the like.
Cost reduction is required.

A first conventional example of an ultrasonic motor will be described with reference to FIG .

In FIG . 6 , the rotor A of the ultrasonic motor is shown.
Is attached to the shaft 5, a moving body 3 fixed to the shaft 5 and having mechanical strength as the rotor A, and attached to the moving body 3, and is pre-pressed by a vibrating body 1 of a stator B described later to rotate. A friction material 4 suitable for transmitting a force to the moving body 3, the shaft 5 is rotatably supported by bearings 6 and 7, the bearing 6 is fixed to a bracket 9, and the bearing 7 is a frame. 10a and 10b are fixed to the bracket 9 and the frames 10a and 10b.
And form an outer case part. The stator B of the ultrasonic motor comprises a vibrating body 1 held by a stator holder 13a fixed to the frame 10a and a piezoelectric body 2 attached to the vibrating body 1.

Then, the spring retainer 9a and the thrust plate 12a
A preload coil spring 8 held by applies a preload to the contact surface between the rotor A, which is rotatably supported by the bearings 6 and 7, and the stator B.

When an electric input is applied to the ultrasonic motor having the above structure to excite the piezoelectric body 2 of the stator B, surface acoustic waves propagate on the surface of the vibrating body 1 in the direction opposite to the rotation direction of the rotor. The surface acoustic wave is a surface wave accompanied by a longitudinal wave and a transverse wave, and a point on the surface of the vibrating body 1 draws an elliptical orbit whose long axis direction is perpendicular to the surface and is parallel to the traveling direction of the surface acoustic wave. Rotate in the direction opposite to the traveling direction. That is, since the surface acoustic wave forms an apex that moves in the direction opposite to the traveling direction of the surface wave on the surface for each wavelength of rotation of the elliptical orbit, the friction material 4 is vibrated by the preload coil spring 8. Body 1
When the friction material 4 is brought into pressure contact with a predetermined pressure, the friction material 4 is driven only in the apexes and is driven in the direction opposite to the traveling direction of the surface acoustic wave, thereby giving a rotational force to the rotor A and the shaft 5
To rotate.

A second conventional example of the ultrasonic motor will be described with reference to FIG .

In FIG . 7 , since the basic structure of the second conventional example is the same as that of the first conventional example, the same components are designated by the same reference numerals and the description thereof will be omitted. What is different is
This is a spring portion, and the preload wave spring 8a is used in the second conventional example.

Since the ultrasonic motor is based on the above principle, in order to efficiently transmit the surface wave to the rotor A, the preload spring must operate smoothly and the amount of preload must be appropriate.

[0010]

However, in the structure of the first conventional example, the spring retainer 9a is required at the preload coil spring 8, and the frame is divided into two parts 10a and 10b. There is a problem that there are many.

Further, since the contact area between the outer surface of the thrust plate 12a for holding the preload coil spring 8 and the inner surface of the bracket 9 is large, the contact between the outer surface of the thrust plate 12a and the outer surface of the thrust plate 12a in order to smoothly transmit the operation of the preload coil spring 8 to the shaft 5. There is a problem in that the machining accuracy of the inner surface of the bracket 9 needs to be increased, which results in a high machining cost, and a defect occurs if the machining accuracy is not sufficient.

Further, there is a problem that the workability of the alignment at the time of assembly is poor because the structure has no automatic alignment function.

Since there is no hole for the bracket 9 on the extension line of the shaft 5 toward the preload coil spring 8 side, the shaft 5
When a pulley or the like is press-fitted to the output side of the shaft 5, the shaft 5 cannot be fixed by inserting a jig from the preload coil spring 8 side, and the force applied to the shaft 5 causes the preload coil spring 8 to move.
There is a problem that the thrust plate 12a may be distorted.

Further, it is necessary to solder the ground wire of the vibrating body 1, but there is a problem that the vibrating body 1 has a large volume and the workability of soldering is poor, and the reliability of soldering is insufficient. .

The structure of the second conventional example has a problem that the number of parts is large, as in the first conventional example.

Further, similarly to the first conventional example, there is a problem that the workability of alignment during assembly is poor.

Further, similarly to the first conventional example, there is a problem that the workability of soldering is poor and the reliability of soldering is insufficient.

The present invention solves the above problems, has a small number of parts, stabilizes the operation of the preload spring, facilitates the aligning work in the assembly process, stabilizes the characteristics, is small in size, and is inexpensive. , To provide an ultrasonic motor.

[0019]

In order to solve the above-mentioned problems, an ultrasonic motor of the present invention includes a stator having a vibrating body and a piezoelectric body for generating a surface acoustic wave on the surface of the vibrating body, and a stator. A stator holder that holds the stator in the axial direction; a rotor that includes a shaft and a friction member that is fixed to the shaft and that contacts the vibrator of the stator; and a preload coil spring that biases the rotor toward the stator to provide a preload. An outer case portion that covers the rotor and the stator, a thrust plate that axially holds the shaft, a frame that constitutes an output side of the outer case portion, and a preload coil spring receiving side of the outer case portion. A bracket, a frame-side bearing that is held by the frame and rotatably supports the shaft, and a shuffle that is held by the bracket. An ultrasonic motor comprising a rotatably supported to the bracket side bearing, said outer case portion and the frame is molded by the molding press working or synthetic resin of the bracketing Tsu DOO and the metal plate only The thrust plate is arranged between the preload coil spring and the bracket-side bearing, and an alignment mechanism portion is formed between the stator holder and the frame-side bearing.

In order to solve the above problems, the ultrasonic motor of the present invention has a thrust plate having a U-shaped cross section in the radial direction.
It is preferable that it is either an inverted U type or an H type.

In order to solve the above-mentioned problems, the ultrasonic motor of the present invention has a thrust plate thickness T1 represented by the distance from the contact surface of the preload coil spring to the contact surface of the shaft,
It is preferable that the free length L1 of the preload coil spring and the distance L2 from the bottom surface of the cylindrical portion of the bracket receiving the preload coil spring to the bracket side bearing have a relationship of L2> L1 + T1.

[0022]

In the ultrasonic motor of the present invention, the outer case portion is composed only of the bracket and the frame, and the frame is formed by pressing a metal plate or forming a synthetic resin, and further, by forming a thrust plate. Since it is arranged between the preload coil spring and the bracket-side bearing, it is possible to stabilize the operation of the preload coil spring while reducing the number of parts. In addition, since the centering mechanism is formed between the stator holder and the frame side bearing, the centering work in the assembly process is simple and the variation in the mutual positional relationship between the rotor and the stator is stable to a small value. It is possible to reduce variations in characteristics.

In the ultrasonic motor of the present invention, the thrust plate can be prevented from warping, tilting or deforming when the radial cross section of the thrust plate is U-shaped, inverted U-shaped or H-shaped.

In the ultrasonic motor of the present invention, the thickness T1 of the thrust plate expressed by the distance from the contact surface of the preload coil spring to the contact surface of the shaft and the free length L of the preload coil spring.
1 and the distance L2 from the bottom surface of the cylindrical portion of the bracket that receives the preload coil spring to the bracket-side bearing, L
By setting the relation of 2> L1 + T1, it becomes unnecessary to hold down the preload coil spring during assembly, and the productivity is improved.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of an ultrasonic motor of the present invention is shown in FIGS.
A description will be given based on FIG.

FIG. 1 shows a basic mold of the right half of this embodiment, and FIGS. 2 to 5 show partial structural examples of this embodiment.

In FIG. 1, the rotor A of the ultrasonic motor is shown.
Is a shaft 5 and a ring-shaped moving body 3 fixed to the shaft 5 and having mechanical strength as the rotor A.
And a ring-shaped friction material 4 which is attached to the moving body 3 and is pre-pressed by the vibrating body 1 of the stator B which will be described later and is suitable for transmitting a rotational force to the moving body 3.
Is rotatably supported by bearings 6 and 7, the bearing 6 is fixed to a bracket 9, and the bearing 7 is a frame 10.
The bracket 9 and the frame 10 form an exterior case portion. The frame 10
In order to reduce the number of steps in the assembly process, a metal plate is pressed or a synthetic resin is used to form an integrated structure.

In the stator B of the ultrasonic motor, the ring-shaped vibrating body 1 and the piezoelectric body 2 attached to the vibrating body 1 are fixed to the self-aligning stator holder 13. The bearing 7 is fixed to the frame 10 and is held by a bearing 7 having an automatic centering mechanism portion 7a.

As described above, the bracket 9 is made of synthetic resin by integrally forming the portion forming the exterior case portion together with the frame 10 and the portion 9a holding the preload coil spring 8 therein. And the shaft 5
Through-hole 14 for fixing the shaft 5 by inserting a jig from the side of the preload coil spring 8 when press-fitting a pulley or the like on the output side of the
Is provided at the top.

FIG. 2 shows a structural example of the portion 9a in which the bracket 9 holds the preload coil spring 8 therein.
That is, the bracket 9 has a step difference between the inner diameter for holding the preload coil spring 8, the inner diameter for holding the thrust plate 12, and the inner diameter for holding the bearing 6.

As shown in FIG. 2, a step X is provided between the inner diameter of the portion holding the preload coil spring 8 and the inner diameter of the portion holding the thrust plate 12, because the diameter of the thrust plate 12 is larger than the diameter of the preload coil spring 8. If it is too large, thrust plate 1
Compared with the case where the diameter of 2 and the diameter of the preload coil spring 8 are equal, the inclination of the preload coil spring 8 can be suppressed,
This is because the preload coil spring 8 expands and contracts smoothly and stabilizes the rotation of the ultrasonic motor. Also, making the thickness of the thrust plate 12 as thin as possible makes it easier to increase the accuracy of rubbing between the thrust plate 12 and the inner surface of the bracket 9 so that the force of the preload coil spring 8 is efficiently transmitted to the shaft 5. Suitable to do.

Further, as shown in FIG. 2, a step Y is provided between the inner diameter of the portion 9a for holding the thrust plate 12 and the inner diameter of the portion for holding the bearing 6 because the positioning is made when the bearing 6 is inserted. This is because it is easy and convenient for eliminating the inclination at the time of insertion.

As shown in the configuration example of FIG. 3, when the thrust plate 12 has a U-shaped, H-shaped, or inverted U-shaped cross section, warpage and deformation can be prevented even if it is thin.

As shown in the configuration example of FIG. 4, the bracket 9 is preloaded against the bracket depth L2 in which the inner diameter portion holding the preload coil spring 8 and the inner diameter portion holding the thrust plate 12 are combined. Free length L of coil spring 8
1 and the thickness of the thrust plate 12 (the thickness from the contact surface of the preload coil spring 8 to the contact surface of the shaft 5 in the case of U-shaped, H-shaped, and inverted U-shaped cross sections) T1 is L1 + T1 <L2 And In this way, when assembled, the parts fit well and the workability is improved.

Then, as shown in the configuration example of FIG. 5, the metal ring 15 spot-welded to the vibrator 1 is attached.
The metal ring 15 is provided with a convex portion 16 for soldering or spot welding the ground wire. By doing so, the workability of attaching the ground wire to the vibrating body 1 is improved, and the reliability is improved.

[0036]

The present invention provides an ultrasonic motor which stabilizes the operation of the preload spring while reducing the number of parts, facilitates the centering work in the assembly process, stabilizes the characteristics, is small in size, and is inexpensive. The effect is obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a first embodiment of an ultrasonic motor according to the present invention.

FIG. 2 is a sectional view showing a partial configuration example of a first embodiment of the ultrasonic motor of the present invention.

FIG. 3 is a sectional view showing a partial configuration example of the first embodiment of the ultrasonic motor of the present invention.

FIG. 4 is a sectional view showing a partial configuration example of the first embodiment of the ultrasonic motor of the present invention.

5A and 5B are a plan view and a side sectional view showing a partial configuration example of the first embodiment of the ultrasonic motor of the present invention.

FIG. 6 is a sectional view showing a configuration of an ultrasonic motor of a first conventional example.

FIG. 7 is a sectional view showing a configuration of an ultrasonic motor of a second conventional example.

[Explanation of symbols]

A rotor B stator 1 vibrating body 2 Piezoelectric body 3 moving bodies 4 Friction material 5 shafts 6 Bearing on the bracket side 7 Frame side bearing 7a Frame side automatic alignment mechanism 8 Preload coil spring 9 bracket 9a cylindrical part 10 frames 12 Thrust plate 13 Stator holder 13a Frame side automatic alignment mechanism 14 through holes 15 metal ring 16 convex

Continuation of front page (56) Reference JP-A-1-264579 (JP, A) JP-A-3-285576 (JP, A) JP-A-62-201074 (JP, A) JP-A-6-121561 (JP , A) JP 5-184166 (JP, A) JP 7-67366 (JP, A) JP 8-317671 (JP, A) Actual flat 2-49390 (JP, U) Actual flat 1-157593 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02N 2/00

Claims (3)

(57) [Claims] 1. A stator having a vibrating body and a piezoelectric body that generates a surface acoustic wave on the surface of the vibrating body, a stator holder that axially holds the stator, a shaft, and a stator fixed to the shaft. A rotor including a friction material that contacts the vibrating body, a preload coil spring that biases the rotor toward the stator to apply a preload, an outer case portion that covers the rotor and the stator, and a thrust that axially holds the shaft. A plate, a frame that constitutes the output side of the exterior case portion, a bracket that constitutes the preload coil spring receiving side of the exterior case portion, and a frame side bearing that is rotatably supported by the frame and rotatably supports the shaft. And a bracket-side bearing that is held by the bracket and rotatably supports the shaft. The exterior case portion is composed only of the bracket and the frame formed by pressing a metal plate or molding a synthetic resin, and disposing the thrust plate between the preload coil spring and the bracket side bearing, An ultrasonic motor comprising an alignment mechanism portion formed between the stator holder and the frame side bearing. 2. The ultrasonic motor according to claim 1, wherein the radial cross section of the thrust plate has a U shape, an inverted U shape, or an H shape. 3. When the thickness of the thrust plate is T1, the free length of the preload coil spring is L1, and the distance L2 from the bottom surface of the cylindrical portion of the bracket receiving the preload coil spring to the bracket bearing is L2> L1 + T1. The ultrasonic motor according to claim 1.