JP2864479B2 - Annular ultrasonic motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a configuration of an ultrasonic motor that generates a driving force by using elastic vibration of a piezoelectric body.

2. Description of the Related Art In recent years, an ultrasonic motor that excites an elastic vibration to a vibrating body using a piezoelectric body such as a piezoelectric ceramic and uses the vibration as a driving force has attracted attention.

Hereinafter, a conventional ultrasonic motor will be described in detail with reference to the drawings.

FIG. 6 is a cutaway perspective view of an annular ultrasonic motor that is excited in a vibration mode of primary radial direction and tertiary or higher in the circumferential direction. The vibrating body 3 is formed by bonding. Protrusions 9 are provided on the vibrator 3 at equal intervals in an annular shape. Reference numeral 8 denotes a friction material made of an abrasion-resistant material, and reference numeral 10 denotes a second elastic body. The moving body 5 is in pressure contact with the vibrating body 3 via the friction material 8. When an electric field is applied to the piezoelectric body 2, a traveling wave of bending vibration is excited in the circumferential direction of the vibrating body 3,
The moving body 5 is driven. Note that the arrow A in the figure indicates the rotation direction of the moving body 5.

FIG. 7 shows an example of the electrode structure of the piezoelectric body 2 used in the annular ultrasonic motor of FIG. In the figure, nine elastic waves are excited in the circumferential direction. A and B are electrode groups each composed of a small region corresponding to a half wavelength, C is an electrode corresponding to three quarter wavelengths, and D is an electrode corresponding to a quarter wavelength. Electrodes C and D are positioned in electrode groups A and B
It is provided to create a phase difference of one-half wavelength (= 90 degrees). The adjacent small electrode portions in the electrodes A and B are polarized in the thickness direction opposite to each other. The bonding surface of the piezoelectric body 2 with the first elastic body 1 is a surface opposite to the surface shown in FIG. 7, and the electrodes are solid electrodes. At the time of driving, the electrode groups A and B are used after being short-circuited, respectively, as shown by oblique lines in FIG.

V ₁ = V ₀ × sin (ωt) (1) V ₂ = V ₀ × cos (ωt) is applied to the electrodes A and B of the piezoelectric body 2 of the annular ultrasonic motor configured as described above. (2) where V ₀ : instantaneous value of voltage ω: angular frequency t: time If voltages V ₁ and V ₂ represented by time are respectively applied, 振動 = ξ ₀ × (cos (ωt) × cos (kx) + sin ( ωt) × sin (kx)) = ξ 0 × cos (ωt-kx) ...... (3) However, ξ: amplitude value of the bending vibration ξ _0: bending the instantaneous value k of the vibration wave number (2π / λ) λ: wavelength x: position A traveling wave of circumferentially traveling bending vibration, which can be expressed by, is excited.

FIG. 8 shows that point A on the surface of the vibrating body 3 performs an elliptic motion of a long axis 2w and a short axis 2u by excitation of a traveling wave, and the moving body 5 placed under pressure on the vibrating body 3 has an elliptical shape. By contact near the vertex, frictional force causes v
= Ω x u.

In the case of such a configuration, in order to increase the speed of the motor, the protrusions 9 for the purpose of increasing the lateral displacement u are arranged at equal intervals and circumferentially over the entire width of the vibrating body 3. Is provided on the contact surface.

However, disposing the protrusions 9 on the vibrating body 3 has a problem in processing. For example, when processing with a milling cutter, the mechanical strength of the base of the protrusion 9 and the vibrating body 3 is weak, and care must be taken in the processing. As a result, there is a problem that the processing time is prolonged. Since the accuracy of the contact surface of the tip of the projection with the moving body 5 is difficult to obtain, the contact surface needs to be polished. Further, the accuracy with respect to the thickness of the vibrating body 3 and the height of the protruding body 9 is directly proportional to the resonance characteristic of the vibration, that is, the deviation of the amplitude ratio of each standing wave component and the resonance frequency in the excitation of the elastic traveling wave. In addition, there is a problem that the demand for the processing accuracy for the height of the projections 9 as well as the thickness is very severe.

Although the motor can be speeded up by providing the projections 9, cogging corresponding to the number of projections appears in the characteristics, which adversely affects the control characteristics. Therefore, if the number of the protrusions 9 is increased, the control characteristics are improved, but problems arise in mechanical strength and workability, and there is a limit in that respect.

In the case of a plate-shaped vibrating body having no projections 9 on the contact surface with the moving body 5, the amplitude of the vibrating body is 10 μm or less, and the pressure contact with the moving body 5 can be performed uniformly and stably. Since it cannot be performed well, there is a problem that the contact position between the moving body 5 and the vibrating body 3 varies and stable motor characteristics cannot be obtained. Further, there is a problem that audible sound is generated due to unstable contact.

Therefore, an object of the present invention is to provide an annular ultrasonic motor that solves the above-mentioned conventional problems.

Means for Solving the Problems The present invention provides a vibrating body in which an annular first elastic body and an annular piezoelectric body are bonded, and a moving body in which an annular friction material and an annular second elastic body are bonded. The moving body is driven by applying pressure to the body and applying an AC electric field to the piezoelectric body to excite the vibrating body in a primary vibration mode in the radial direction and to excite an elastic traveling wave in the circumferential direction. In the annular ultrasonic motor, the contact surface between the vibrating body and the moving body does not reach the outer peripheral edge of the vibrating body, reaches the inner peripheral edge, and the vertex surface of the first elastic body A recess substantially equal to the plate thickness is formed to reduce the rigidity of the first elastic body on the inner peripheral edge side.

The ring-shaped ultrasonic motor of the present invention has a ring-shaped first elastic member and a ring-shaped piezoelectric member bonded together, a ring-shaped friction material and a ring-shaped second elastic member bonded together. The moving body is in pressurized contact, and exciting a traveling wave of vibration in the circumferential direction of the vibrating body by applying an electric field to the piezoelectric body,
By forming a concave portion that drives the moving body and that does not reach the outer peripheral edge of the vibrating body but reaches the inner peripheral edge thereof on a contact surface of the vibrating body with the moving body, the output characteristic is improved. Will be excellent.

Embodiment Hereinafter, an embodiment of an annular ultrasonic motor according to the present invention will be described in detail with reference to the drawings.

1 (a) and 1 (b) are a plan view and an end view of a vibrating body of an annular ultrasonic motor according to the present invention. In the figure,
The first elastic body 1 forms an annular vibrating body 3 together with the piezoelectric body 2, and a concave portion 4 is provided inside the annular vibrating body 3 in a plane width that does not reach the outer diameter. The recesses 4 are preferably provided at equal intervals in the circumferential direction as shown in FIG. 1, but are not limited thereto.

As shown in FIG. 6, the moving body 5 is in pressure contact with the vibrating body 3 provided with the concave portion 4 which does not reach the outer diameter of the annular vibrating body 3 via the friction material 8 as shown in FIG. .

The shape of the concave portion 4 may be a partially hollow shape as shown in FIG. 2 (a), a rectangular shape as shown in FIG. 2 (b), or FIG. 2 (c). As shown in FIG. 1), various shapes such as a V-shaped saw-like cutout can be considered, but are not limited thereto.

FIG. 3 shows the distribution of vibration displacement in the radial direction of the vibrating body of the annular plate. As the primary vibration mode is used, the displacement increases toward the outer side. However, by providing the recess 4 reaching the inner peripheral edge of the vibrating body 3, the mechanical rigidity changes in proportion to the cube of the plate thickness, so that the displacement amount can be flattened in the radial direction. Stable contact is possible even with eccentricity. On the other hand, since the movable body is driven inside the small amplitude of the vibrating body 3, it is stable against a change in load.

Next, the operation of the embodiment of the annular ultrasonic motor according to the present invention will be described.

By using the simple, basically flat annular vibrating body 3 as described above, problems in processing (accuracy, cost, etc.) can be solved as in the prior art. In addition, since precision is not required for the size and shape of the concave portion 4, integral molding such as powder metallurgy, which can be reduced in cost, becomes possible.

If the depth of the concave portion 4 is equal to or more than the amount by which the moving body 5 is deformed toward the vibrating body 3 by pressurization, basically no further depth of the concave portion 4 is particularly required.

Further, since the number of the concave portions 4 can be freely set, a motor having stable characteristics with little cogging can be obtained by increasing the number.

In addition, since there is an increase in frictional resistance due to the catching of the concave portion 4, it is possible to obtain an excellent annular ultrasonic motor having stable characteristics and free from a sudden fluctuation in output due to slippage on the high torque side. Can be.

As in the past, the effect on the resonance characteristics due to the change in the mechanical rigidity and the change in the thickness of the vibrating body due to the protrusions can be made very small, causing audible sound and uneven rotation during elastic traveling wave driving. No unnecessary standing wave components are generated.

It is needless to say that the recesses 4, 6, 7 may be provided on the contact surface of the moving body 5 with the vibrating body 3. At this time,
The concave portions 4, 6, 7 of the vibrating body 3 are not always necessary.

Effect of the Invention In the present invention, by providing a concave portion in the contact surface with the moving body with respect to the width of the vibrating body, the processing of the vibrating body is simplified to a flat plate shape, and processing accuracy is easily obtained. In addition, because the mechanical output can be transmitted efficiently due to caught by the concave part, etc., a ring type ultrasonic motor with good stability, high reliability and excellent output characteristics without cogging or audible sound is realized. You can do it.

[Brief description of the drawings]

FIG. 1 (a) is a plan view of a vibrating body of an embodiment of an annular ultrasonic motor according to the present invention, FIG. 1 (b) is an AA 'end view thereof, FIG. (B) and (c) are cross-sectional views showing examples of the shape of the concave portion of the embodiment, FIG. 3 is a diagram showing a radial vibration displacement distribution in a thin plate of an annular ultrasonic motor, and FIG. Cutaway perspective view of ultrasonic motor, FIG.
FIG. 6 is a plan view showing the shape and electrode structure of a piezoelectric body used in the ultrasonic motor shown in FIG. 6, and FIG. 6 is an explanatory diagram of the operation principle of the ultrasonic motor. 2 ... Piezoelectric body, 3 ... Vibration body, 4 ... Recess, 5 ... Movable body, 8 ... Friction material.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Masanori Sumihara 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. In-company (56) References JP-A-2-26278 (JP, A) JP-A-2-17875 (JP, A) JP-A-63-206175 (JP, A) ) Hikaru 1-86489 (JP, U)

Claims (1)

(57) [Claims] 1. A pressurized contact is made between a vibrating body in which an annular first elastic body and an annular piezoelectric body are bonded, and a moving body in which an annular friction material is bonded with an annular second elastic body. And applying an AC electric field to the piezoelectric body to excite the vibrating body in a primary vibration mode in the radial direction and to excite an elastic traveling wave in the circumferential direction to drive the moving body. In the motor, a contact surface between the vibrating body and the moving body does not reach an outer peripheral edge of the vibrating body but reaches an inner peripheral edge thereof, and a vertex surface is substantially equal to a plate thickness of the first elastic body. Forming a recess, the first
An annular ultrasonic motor wherein the rigidity of the inner peripheral edge side of the elastic body is reduced.