JPS62247769A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To reduce power consumption by a method wherein a stator and a rotor are held so that they are coupled with or separated from each other, and controlled to have a pressed state or non-pressed state at suitable time by means of a laminated piezoelectric actuator. CONSTITUTION:A stator comprising a piezoelectric element 11 and a vibration plate 12 is fixed within a cylindrical body 10 as stator/rotor holding means by a fixing element 14. A rotor 13 is arranged on the stator so that they are coupled with or separated from each other, and a laminated piezoelectric actuator 16 is installed through a bearing 15. Contact portion between one end surface of the actuator 16 and an upper surface of the bearing 15, and contact portion between other end surface of the actuator 16 and inside of an upper wall of the body 10 are fixed. At AUTO operation state, if voltage is applied to the actuator 16, it is extended and the rotor 13 and the stator are contacted. Also at MANUAL state, the applied voltage is turned off and the pressing force is released. As a result, the changing control can be performed stably and rapidly.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an ultrasonic motor configured so that the rotor rotates with respect to the stator by pressing the rotor against the stator in which surface traveling waves are excited. In particular, the present invention relates to improvements in pressure contact means between a stator and a rotor.

[Conventional technology]

Recently, ultrasonic motors have been attracting attention as a new motor to replace electromagnetic motors. This ultrasonic motor is not only new in principle, but also has the following advantages over conventional electromagnetic motors.

■Does not require a central axis.

■Thin and lightweight.

■There is no exchange of magnetic influence.

■The component structure is simple and highly reliable.

■Low speed and high torque can be obtained without gears.

■There is no backlash and positioning is easy.

■The rotor rotates and chucks against the stator.

It can take on three states: floating.

In order to take advantage of these advantages, various applied techniques are being researched.

FIG. 8 is a schematic diagram of a typical conventional rotary ultrasonic motor. The principle of this ultrasonic motor is that an annular piezoelectric element 1
A traveling wave is excited by the inverse piezoelectric effect in the metal donut-shaped diaphragm 2 integrated with the metal donut-shaped diaphragm 2, and the rotor 3 is suppressed and arranged so as to be in contact with the apex of the backward elliptical trajectory of the surface mass point generated thereby. 3 in the direction of arrow A. The above traveling wave excitation method will be explained below.

FIG. 9 is a diagram showing a polarization state diagram of the piezoelectric element 1 constituting a general ultrasonic motor, and corresponds to the diagram seen from below in FIG. 8. Polarize the ring-shaped piezoelectric material so that the polarization directions are alternately reversed like ■○■○... or arrange multiple divided piezoelectric elements so that the polarization directions are opposite to each other. do.

In such an arrangement, one set of adjacent polarization directions opposite to each other corresponds to one wavelength λ. and,
180@ Unpolarized portions 1a and 1b having lengths of 3/4λ and 1/4λ are arranged at different positions, respectively, and polarized bodies are arranged symmetrically with respect to the center line connecting these parts. The polarization directions are continuously arranged so that the polarization directions are alternately opposite in the circumferential direction.

Of this polarization arrangement, the left half of the surface that is not in contact with the diaphragm, with the 3/4λ and 1/4λ unpolarized parts 1a and 1b sandwiched between them, is covered with one electrode, and this is connected to one side of the common electrode. The surface of the right half not in contact with the diaphragm is covered with another electrode, and this is used as the common electrode on the other side. The electrode on the diaphragm side is electrically connected to the diaphragm 2, and is shared as a ground-side electrode for all piezoelectric elements.

When driving a structure having such a polarization arrangement and electrode arrangement, there is a phase difference of π/2 between the two common electrodes on one side and the ground side electrode, and λ.

An electric signal having a natural frequency ω determined by the inner and outer diameters of the ring, the thickness, the average elastic constant of the piezoelectric ceramic and the diaphragm, the density 9, etc. is input.

Now, as shown in FIG.
When an AC voltage of frequency ω is applied from the power source 5, the diaphragm 2
A bending standing wave is excited.

When the above AC voltage is applied to the left part of the piezoelectric element 1 in FIG.
A standing wave having a displacement of nωt (1) is excited. Furthermore, when an AC voltage with a frequency ω whose phase is shifted by π/2 from the above AC voltage is applied to the right side portion of the piezoelectric element 1 in FIG.
The neutral axis of the diaphragm 2 has y2-As in2π/λ(p
-λ/4) sin (ω is one π/2) ... (2
) is excited.

Therefore, when the AC voltages shown in equations (1) and (2) above are simultaneously applied to the right and left halves of the piezoelectric element 1, V−V1+V2 −As i n (2πp/λ−ωt)・−・A traveling wave with a displacement of (3) is obtained. A surface traveling wave having the same phase as the neutral axis is also excited on the surface of the diaphragm 2. In such a bending traveling wave of a plate, as shown in FIG. 10, the mass point on the surface moves backward in an elliptical direction -5 in the direction of wave propagation. Therefore, when the rotor 3 is placed on the surface of the diaphragm 2 by pressing it with a certain pressure as shown in FIG. It will rotate.

[Problem that the invention seeks to solve]

When such an ultrasonic motor is used as a lens barrel drive source of a camera, the following problems arise. That is, when used as a lens barrel drive source of a camera, etc., it is necessary to support not only AUTO operation but also MANUAL operation. However, in the ultrasonic motor, the rotor 3 is suppressed and held against the diaphragm 2 of the stator for efficiency reasons, so simply turning off the power to the ultrasonic motor during manual operation will not cause the rotor The suppressing holding force of 3 becomes a large resistance, and strong force is required for operation. As a means to deal with such problems, 1) means 2 which switches from the traveling wave mode to the standing wave mode during MANUAL operation, eliminates the relative movement in the rotational direction between the rotor 3 and the diaphragm 2, and at the same time reduces the contact friction force; ) At the time of MANUAL operation, a means to separate the rotor and stator may be considered.

However, with the method 1), it is necessary to supply power to the stator to excite the bending wave even during the MANUAL operation, so there is a drawback that the power consumption increases and becomes uneconomical. In addition, with the method 2), although there is no risk of a significant increase in power consumption, there is a problem in that after the stator and rotor are once separated, it is difficult to bring them into pressure contact again stably and quickly. .

Therefore, the present invention provides an AUTO-MA system that can stably and quickly switch the stator and rotor into a pressure-contact state or a non-pressure-contact state at a predetermined pressure, and which requires almost no power consumption.
An object of the present invention is to provide an ultrasonic motor equipped with NUAL switching means.

[Means for solving problems]

In order to solve the above-mentioned problems and achieve the object, the present invention takes the following measures. That is, in an ultrasonic motor configured so that the rotor rotates relative to the stator by pressing the rotor against the stator in which surface traveling waves are excited, the stator and rotor are held by a holding means so as to be able to come into contact with and separate from the rotor. At the same time, the stator and rotor, which are held by the holding means so as to be able to come into contact with each other and separate from each other, are controlled to be in a press-contact φ or non-press-contact state at appropriate times by a laminated piezoelectric actuator.

Note that as the laminated piezoelectric actuator, one provided with an elastic part for pressing may be used.

[Effect]

By taking such measures, when voltage is applied to the laminated piezoelectric actuator during AUTO operation,
The actuator extends, and the rotor and stator come into contact with a certain pressure, making it possible to perform AUTO operation. Furthermore, when the voltage applied to the laminated piezoelectric actuator is turned OFF (-0) during MANUAL operation, the actuator contracts and the pressure contact between the rotor and the stator is released, making it possible to respond to MANUAL operation. In this way, the stator and rotor are stably and quickly controlled to be in a pressure contact state or a non-pressure contact state by the laminated piezoelectric actuator.

〔Example〕

FIGS. 1(a) and 1(b) are cross-sectional views showing the configuration of the first embodiment of the present invention, and FIG. 1(a) shows the state during AUTO operation,
(b) shows the state during MANUAL operation.

As shown in FIGS. 1(a) and 1(b), a stator.

A stator consisting of a piezoelectric element 11 and a diaphragm 12 is fixed inside a cylindrical body 10 serving as a rotor holding means by a fixing element 14 such as a screw. A rotor 13 is disposed on the stator L so as to be able to come into contact with and separate from the stator. A laminated piezoelectric actuator 16 is mounted between the surface of the rotor 13 and the inner surface of the upper wall of the body 10 via a bearing 15. The joint between one end surface of the multilayer piezoelectric actuator 16 and the negative surface of the bearing 15 and the joint between the other end surface of the multilayer piezoelectric actuator 16 and the inner surface of the upper wall of the body 10 are fixed by adhesive or other means. There is.

Figure 2 shows the bearing 15 and the laminated piezoelectric actuator 1.
6 is a diagram showing the arrangement relationship with 6. FIG. As is clear from FIG. 2, the laminated piezoelectric actuator 16 has a bearing ball 15a of the bearing 15.

It is arranged at an intermediate position between 15b and 15c.

In the ultrasonic motor of this embodiment configured as described above, when voltage is applied to the laminated piezoelectric actuator 16 during AUTO operation, the actuator extends as shown in FIG. Pressure force is applied between the diaphragm 12 and the diaphragm 12 . When a motor drive voltage is applied to the piezoelectric element 11 of the stator in this state,
A bending traveling wave is excited in the diaphragm 12, and the rotor 13 rotates. In this way, it becomes possible to support AUTO operation.

Furthermore, when the voltage applied to the laminated piezoelectric actuator 16 is turned off during MANUAL operation, as shown in FIG.
As shown in , the actuator is retracted, and the pressure force between the rotor 13 and the diaphragm 12 in the stator is removed.

As a result, a slight gap G is generated between the bearing 15 and the rotor 13, and the frictional resistance between the rotor 13 and the diaphragm 12 is reduced. If the rotor is manually rotated in this state, the rotor 13 will easily rotate with a small force. In this way, it becomes possible to correspond to MANUAL operation.

FIG. 3 is a diagram showing the relationship between displacement and stress in a typical laminated piezoelectric actuator. As is clear from FIG. 3, the laminated piezoelectric actuator has a relatively small amount of displacement, but can generate a large stress. Furthermore, the laminated piezoelectric actuator has excellent high-speed response.

Therefore, if the laminated piezoelectric actuator 16 in this embodiment has the characteristics shown in FIG. 3 and the gap G during MANUAL operation is set to 5p+, then when a voltage of 200V is applied, Maximum 2.5X1
The mouth 13 can be brought into pressure contact with the diaphragm 12 of the stator with a stress of 0.07 (N/m2). Furthermore, since the response time of the laminated piezoelectric actuator is 1 m5ec or less, it can respond at high speed.

In this way, in this embodiment, the rotor 13 and the diaphragm 1
Since pressure contact and non-pressure contact with 2 are performed by the laminated piezoelectric actuator 16, the AUTO-MANUA
L can be switched quickly and stably. Furthermore, since the laminated piezoelectric actuator 16 expands and contracts by applying a DC voltage, it requires very little power consumption when turned on and off.For example, when using a battery as a power source, the battery capacity It can be small and economical.

FIGS. 4(a) and 4(b) are cross-sectional views showing the structure of a second embodiment of the present invention shown in correspondence with FIGS. 1(a), (b) and 1. This embodiment differs from the first embodiment in that a recess 12a is provided in the diaphragm 12 of the stator, and the tip of the fixing element 14 is loosely inserted into this recess 12a, and the entire stator is held so as to be movable up and down. , a laminated piezoelectric actuator 16 is installed between the piezoelectric element 11 of the stator and the inner surface of the bottom wall of the body 10. Note that the stator can only move up and down to a certain extent and is prevented from rotating.

In this embodiment, when a voltage is applied to the laminated piezoelectric actuator 16 during AUTO operation, as shown in FIG.
), the stator is pushed up and pressure is applied between the diaphragm 12 and the opening 13. Also MANUAL
When the above voltage is turned off during operation, the voltage shown in Fig. 4 (b
), the stator is pulled down and the pressure between the diaphragm 12 and the rotor 13 is removed. This embodiment also provides the same effects as the first embodiment.

FIGS. 5(a) and 5(b) are sectional views showing the structure of a third embodiment of the present invention. This embodiment differs from the first embodiment in that a coil spring 17 as a pressing elastic member is attached to the laminated piezoelectric actuator 16 in a compressed state.

131 In this embodiment, when a voltage is applied to the laminated piezoelectric actuator 16 during AUTO operation, as shown in FIG.
), the actuator expands, and the compressed coil spring 17 expands accordingly, the expansion force presses the bearing 15, and press force is applied between the rotor 13 and the diaphragm 12. Furthermore, when the voltage is turned off during MANUAL operation, the actuator contracts as shown in FIG. The pressure force between the rotor 13 and the diaphragm 12 is removed. In this embodiment, since the pressing force is obtained by the coil spring 17, the laminated piezoelectric actuator 16 only needs to exert control force, and may be small. Other than the above, the same effects as in the first embodiment are achieved.

FIGS. 6(a) and 6(b) are diagrams showing the configuration of a fourth embodiment of the present invention. This embodiment differs from the third embodiment in that the laminated piezoelectric actuator 16 and the spring coil 17 are arranged below the stator.
This is similar to the difference from the example. However, in the case of this embodiment, a suppression plate 18 is interposed on the lower surface of the piezoelectric element 11.

This embodiment is similar to the second embodiment in that the entire stator is moved up and down to bring the rotor 13 and the diaphragm 12 into pressure contact or non-pressure contact, and the coil spring 17
The effect is similar to that of the third embodiment. Other than the above, 1st
The same effects as in the embodiment are achieved.

FIGS. 7(a) and 7(b) are sectional views showing the structure of a fifth embodiment of the present invention. This embodiment differs from the first embodiment in that a flange 13a is provided at the top of the shaft of the rotor 13, and a coil spring 20 for lifting the rotor is interposed between the flange 13a and the outer surface of the upper wall of the body 10 via a bearing 19. This is the point.

In this embodiment, when the voltage applied to the laminated piezoelectric actuator 16 is turned off during MANUAL operation, the rotor 13 is pulled upward by the coil spring 20 for lifting the rotor, so that the gap G between the rotor 13 and the diaphragm 16 is It definitely occurs between. As a result,
Even if the weight of the rotor 13 is considerably large, no pressing force will act between it and the diaphragm 12. Therefore, M.A.
In addition to making NUAL operations easier, even MANUAL
Even if the operation is performed for a long time, there is no risk of wear on the contact surface between the rotor 13 and the diaphragm 12, and deterioration of characteristics can be prevented.

Other than the above, the same effects as in the first embodiment are achieved.

Note that the present invention is not limited to the above embodiments.

For example, the rotor pulling means shown in FIGS. Third. It may be applied to each of the fourth embodiments, and in that case, the same effects as those of the fifth embodiment can be expected. It goes without saying that various other modifications can be made without departing from the gist of the present invention.

〔Effect of the invention〕

According to the present invention, the stator and rotor are held in contact with and separated from each other, and the stator and rotor are controlled to be in pressure contact or non-pressure contact state at appropriate times by the laminated piezoelectric actuator. AUTO-MAN that can stably and quickly switch the pressure contact state or non-pressure contact state at a predetermined pressure, and requires almost no power consumption.
An ultrasonic motor equipped with UAL switching means can be provided.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are cross-sectional views showing the configuration of the first embodiment of the present invention. FIG. 1(a) is a diagram showing the operating state during AUTO operation, and FIG. It is a figure showing a state. FIG. 2 is a diagram showing the arrangement relationship between the bearing 15 and the laminated piezoelectric actuator 16 of the same embodiment, and FIG. 3 is a diagram showing the relationship between displacement and stress of a typical laminated piezoelectric actuator. Figures 4(a) and (b) are similar to Figures 1(a) and (b).
5(a) and 5(b) are cross-sectional views showing the configuration of the second embodiment of the present invention shown in correspondence with FIGS. 1(a) and (b). A sectional view showing the configuration of an example,
6(a) and 6(b) are cross-sectional views showing the configuration of a fourth embodiment of the present invention corresponding to FIGS. 1(a) and (b), and FIGS. FIG. 1 is a sectional view showing the configuration of a fifth embodiment of the present invention corresponding to FIGS. 1(a) and 1(b). Figures 8 to 10 are diagrams showing the prior art. Figure 8 is a schematic diagram of a typical conventional rotary ultrasonic motor, and Figure 9 is a diagram of a piezoelectric element constituting a general ultrasonic motor. A diagram showing a polarization state diagram, and FIG. 10 is a diagram showing the rotation principle. DESCRIPTION OF SYMBOLS 11... Piezoelectric element, 12... Vibration plate, 13... Rotor, 14... Fixed element, 15... Bearing, 1
6... Laminated piezoelectric actuator, 17... Coil spring, 18... Pressing plate, 19... Bearing, 20... Coil spring for pulling up the rotor. Applicant's representative Patent attorney Atsushi Tsuboi l-L'uJ Mouth ≧ (LL+r/) 7J'yk ♀゛Procedural amendments Showa, 2617 June Kunio Ogawa, Commissioner of the Patent Office 1, Case indication patent application 1988- 08941.8 No. 2, Name of the invention Ultrasonic motor 3, Relationship with the person making the amendment Patent applicant (037) Olympus Optical Industry Co., Ltd. 4, Agent UBE Building, 3-7-2 Kasumigaseki, Chiyoda-ku, Tokyo 7,
Contents of amendment (1) Among the drawings, Figure 1 (a) (b) and Figure 4 (a)
(b), Figures 5 (a) and (b), Figures 6 (a) and (b), Figures 7 (a) and (b), and Figure 9 are corrected as shown in the attached sheet. (2) "Rotary ultrasonic motor" in line 19 of page 2 of the specification is corrected to "annular ultrasonic motor." (3) In the second line of page 5 of the specification, after "to," add the phrase "assuming the amplitude as A and the position in the circumferential direction along the neutral axis as p". (4) In the 6th line of page 8 of the specification, ``to have together'' has been corrected to ``to have together''. (a) 1st (b) Figure

Claims (2)

[Claims] (1) In an ultrasonic motor configured so that the rotor rotates relative to the stator by pressing the rotor against the stator in which surface traveling waves are excited, holding that holds the stator and rotor so that they can come into contact with and separate from each other. and a laminated piezoelectric actuator for controlling the stator and rotor, which are held by the holding means so as to be in contact with and separate from each other, into a pressure contact state or a non-pressure contact state. (2) The ultrasonic motor according to claim 1, wherein the laminated piezoelectric actuator includes an elastic member for pressing.