JPH04145880A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To obtain an effective and highly efficient ultrasonic motor by constituting the motor of an annular elastic body and a plurality of electro/mechanical conversion elements fixed to the elastic body and forming a flexible vibrator to a closed curve shape by applying an SC voltage across the electro/mechanical conversion elements. CONSTITUTION:When a prescribed high-frequency voltage is applied across piezo-electric elements 4 firmly stuck to a flexible vibrator 10, resonant flexible standing waves are produced on the ring. The arrangement the elements 4 which can most efficiently produce the standing waves is that the elements 4 are firmly stuck to an elastic body 5 at every 1/2 wavelength, with the direction of polarization of the piezoelectric bodies constituting the elements 4 being alternately inverted. Then a high-frequency voltage which has the same frequency as that of the high-frequency voltage applied to the vibrator 10 and a 90 deg. phase difference against the voltage applied to the vibrator 10 is applied across longitudinal vibrators provided at the node positions of the flexible standing waves at an equal distance on a circumference. Then elliptical vibrations are produced on the leading end face of the vibrator 12 and rotate a rotor 7 which is brought into pressurized contact with the end face.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an ultrasonic motor, and more particularly, to an ultrasonic motor that has a hollow-shaped driving body and drives a driven body by the driving body. .

[Prior Art] In recent years, as is well known, ultrasonic motors have attracted attention as actuators that can drive focusing operations of camera lenses and the like in a small space. The reason for this is that ultrasonic motors can obtain large torque at lower speeds than conventional electromagnetic motors, so they can drive the lens holding frame directly, so there is no need for reduction gears, and they are compact, silent, and highly accurate. This is because high-response lens drive can be achieved.

By the way, when using an ultrasonic motor as an actuator for driving a camera lens, the actuator can be installed within the hollow cylindrical frame that houses the lens holding frame without taking up space, but its shape and arrangement must be consistent. It requires some ingenuity.

And, as a product that realized this, Japanese Patent Application Laid-Open No. 122267
There is an annular ultrasonic motor using a traveling wave, which is disclosed in Japanese Patent No. 2. This generates a traveling wave in the circumferential direction of a ring-shaped vibrator, presses the end of a cylindrical body as a rotor to the end face where the traveling wave is generated, and rotates the cylindrical body. In order to convert the rotation of the body into linear movement of the lens, a conversion mechanism such as a cam or a helicoid screw is provided on the cylindrical body, and this mechanism moves the lens forward and backward in the optical axis direction.

Furthermore, as disclosed in Japanese Patent Publication No. 60-7245, a lens has been proposed in which an inchworm type actuator is provided in the lens to drive the lens in a straight line. This is designed to drive the lens holding frame in a straight line by sequentially operating two actuators for clamping and one actuator for driving.

Furthermore, as seen in Japanese Unexamined Patent Publication No. 62'-99714, a traveling wave type rail-shaped linear motor is arranged around the outer periphery of the lens holding frame, and the lens holding frame is moved by the progressive vibration waves generated in the linear motor. Some are configured to drive.

However, in order to drive the lens with the annular ultrasonic motor using traveling waves disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 1-222672, the rotational motion generated in the motor must be controlled as described above. A conversion mechanism such as a helicoid screw or a cam is required to convert the motion into linear motion, and if a hollow motor is constructed, it will be large and the construction will be complicated. Furthermore, since a helicoid screw or cam is used, there is also a drawback that it is difficult to accurately determine the positional accuracy of the lens holding frame due to mechanical play.

Furthermore, with the inchworm type actuator shown in the above-mentioned Japanese Patent Publication No. 60-7245, which uses the inchworm type actuator to drive the lens, due to its operating mechanism, it is not possible to realize a step frequency of about several KHz. However, the clamping actuator has the disadvantage of slow operation speed, and the clamping actuator must hold the lens frame fixedly on the fixed frame when clamped, and be completely separated from the fixed frame when not clamped. A laminated piezoelectric material is used, and its operating stroke is several micrometers to several tens of micrometers, and abrasion of the clamping surface may cause the clamping operation to become unstable and the lens drive to stop. Furthermore, in order to hold the lens in a certain position, it is necessary to keep the actuator energized to keep it in a clamped state, which also causes the problem that energy is consumed even when the lens is not in operation.

On the other hand, the traveling wave type linear ultrasonic motor disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 62-99714 requires a closed-loop shaped vibrator to be disposed around the outer periphery of the lens to generate a traveling wave. Using a damping material increases the size of the lens frame, and since traveling waves are used, it is difficult to fix the transducer without damaging the vibration. The position of the lens relative to the member in the direction perpendicular to the lens optical axis cannot be precisely determined.

Therefore, in order to eliminate the above-mentioned drawbacks of the conventional ultrasonic motor of this type, the present applicant has generated a resonant bending standing wave in a plate-shaped bending vibrator to which a piezoelectric material is attached, and the position of the bending vibration node is A vertical vibrator made of a laminated piezoelectric material vibrates in a direction perpendicular to the neutral axis of the bending vibration.
A small linear type ultrasonic motor is configured to generate elliptical vibration at the tip of the vertical vibrator by sliding the vertical vibrator, thereby moving a moving body crimped to the tip of the vertical vibrator in a predetermined direction. I proposed it earlier (patent application No. 2-7980)
No. 0).

[Problems to be Solved by the Invention] However, in the ultrasonic motor that uses minute rotational motion around nodes of flexural vibration, which was previously proposed by the present applicant, a plurality of circular drive bodies are arranged side by side to generate a rotary type motor. When manufacturing a motor, since the bending vibrator has an end, energy loss occurs due to reflection at the end, making it impossible to manufacture a highly efficient rotary motor.

That is, the bending waves generated by the expansion and contraction of the piezoelectric body, which is an electro-mechanical transducer, propagate left and right in the longitudinal direction of the plate and are reflected at each end face of the plate. Each wave overlaps to form a standing wave, but since the plate has an end face, energy loss occurs due to wave reflection there. In other words, there is no problem if the wave reflection at the end is 100%, but in reality, the reflection at the end is not 100%, but 100%.
A loss occurs with each reflection.

In addition, in a rod-shaped bending vibrator with ends, the amplitude of the standing wave varies depending on the position, and the bending vibration that occurs near the center of the vibrator is the largest, and the amplitude of the bending vibration that occurs at the ends is small. The mounting position of the vertical vibrator is limited. That is, unless a longitudinal vibrator is installed at the node position of the minute rotational amplitude, a difference will occur in the amplitude, and the difference in amplitude will cause the ultrasonic motor to slip, resulting in energy loss.

Furthermore, in the traveling wave type annular ultrasonic motor disclosed in Japanese Patent Application Laid-Open No. 1-222672, since traveling waves are generated in the vibrator, it is difficult to support it without losing efficiency.
Efficiency is not necessarily high.

An object of the present invention is to solve the above-mentioned drawbacks of the conventional ultrasonic motor by making the bending transducer into a closed curve shape, and to provide a highly efficient rotary ultrasonic motor that is effective for driving camera lenses, etc. .

[Means for Solving the Problems and Effects] The ultrasonic motor according to the present invention includes an annularly formed elastic body and a plurality of electromechanical transducer elements fixed to the elastic body, a bending vibrator that generates standing wave type bending vibration on the elastic body by applying an alternating voltage to the element; A vertical vibrator that is oscillated about the nodal line by bending vibration and expands and contracts in the amplitude direction of the bending vibration when an alternating current voltage is applied, and a driven member that is pressed against the tip surface of the vertical vibrator. By expanding and contracting the longitudinal vibrator in synchronization with the bending vibration, the driven member is moved relative to the bending vibrator and the longitudinal vibrator in the wavelength direction of the bending vibrator. It is characterized by causing

[Example] The present invention will be explained below with reference to illustrated embodiments.

1 and 2 show a first embodiment of the present invention, in which a fixed frame 1 has an outward flange on its lower end outer layer on which a driving body 15, a driven member 7, etc. are placed and attached. 1
a, and is formed of a cylindrical body with internal threads 1b carved on the outer circumferential surface of the upper end for screwing the retaining ring 11, and is located at three equally spaced positions on the outer circumferential edge of the flange 1a. Each of the receivers of the bending vibrator 10 is provided with a portion IC. The receiver part IC has a recess 1d into which a support pin 5a provided on the bending vibrator 10 is fitted and supported via a support 14, and the support 14 is made of, for example, rubber, urethane, etc.
The bending vibrator 1 is made of a vibration-proofing material such as felt.
It is designed to allow vibration around the 0 node line and also serve as a vibration damper for the driving body 15.

The driving body 15 is composed of a bending vibrator 10 and a longitudinal vibrator 12.

The bending vibrator 10 is formed by fixing a large number of piezoelectric elements 4, which are a plurality of electro-mechanical conversion elements, to the lower surface of a ring-shaped elastic body 5, and applies a driving AC voltage to the piezoelectric elements 4. This serves to cause the bending vibrator 10 to generate bending standing wave vibration in the thrust direction. Further, on the upper surface of the elastic body 5 of the ring-shaped bending vibrator 10, longitudinal vibrators 12 that vibrate in the amplitude direction of the bending vibration are provided at three locations among the nodal lines of the bending vibration. A cylindrical rotor 7, which is a driven member, is in contact with the longitudinal vibrator 12 via a slider 6 that is integrally attached to the lower surface of the rotor. The rotor 7 has its inner circumferential surface fitted to the outer circumferential surface of the cylindrical body of the fixed frame 1 with a gap, and is rotatably disposed, and has a ball receiving groove 7 formed of a V-groove in the middle of its upper end surface.
A is bored in a ring shape. In this ball receiving groove 7a, a large number of balls 8 that reduce rotational friction similar to ball bearings are arranged in a row, and a ball holding ring 9 that is tightly fitted to the outer circumferential surface of the fixed frame 1 is placed above the balls 8. A ring-shaped leaf spring 13 is disposed on the upper surface of the retaining ring 9, and the retaining ring 11 is screwed into the female thread 1b of the fixed frame 1.

The rotor 7 is fixed to the lower surface of the rotor 7 by screwing the retaining ring 11 into the female thread 1b of the fixed frame 1, so that the spring 13 disposed on the upper surface of the ball retaining ring 9 presses the rotor 7 via the balls 8. The lower surface of the slider 6 and the upper surface of the vertical vibrator 12 are pressed together and pressed together.

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

When a predetermined high-frequency voltage is applied to the piezoelectric element 4 fixed to the bending vibrator] 0, a resonant bending standing wave is generated on the ring. The standing wave of bending occurs at a wavelength that equally divides the circumference, and in this example, the frequency is selected such that a standing wave with a wave number of 3n (n = 1.2.3...) is generated. There is. The piezoelectric element 4 can be arranged to most efficiently generate the standing wave by fixing the piezoelectric element 4 to the elastic body 5 with the polarization direction of the piezoelectric element 4 alternately reversed every 1/2 wavelength. Next, a high-frequency voltage of the same frequency is applied to the vertical vibrators 12 provided at equal positions on the circumference at the node positions of the bending standing wave, and a high-frequency voltage having a phase approximately 90° different from the high-frequency voltage applied to the bending vibrator 10 is applied. Apply wave voltage. However, the phase of the bending vibration with the longitudinal vibrator 12 attached]
If the difference is 80°, the phase of the longitudinal vibration is changed by 180°. In the case of FIG. 1, the phases of the longitudinal vibrations are all the same. Then,
Elliptical vibration occurs at the end face of the vertical vibrator 12, causing the rotor 7 pressed against the end face to rotate. In the case of reversal, the phase of either the bending vibration or the longitudinal vibration may be changed by 1800 degrees.

According to this embodiment configured in this manner, the driving body 15 is reliably held on the fixed frame 1 at the nodes of bending vibration, so that the vibration energy of the driving body 15 is less likely to be lost due to support. Further, although the drive body 5 receives a force in the rotational direction as a reaction to the rotation of the rotor, it does not rotate because the support pin 5a is engaged with the four parts 1d. Further, by positioning the support at three equally divided positions on the circumference, the position of the driving body 11.5 with respect to the fixed frame 1 is determined accurately.

FIG. 3 shows only a driving body 15A in a second embodiment of the ultrasonic motor of the present invention, and the configuration other than this driving body 15A is the same as that of the first embodiment. Also, in FIG. 3, support pins provided integrally with the elastic body 5A are not shown, or the support pins are provided at four locations at the nodes of bending vibration where the longitudinal vibrator 12A is arranged. There is. In this embodiment, the piezoelectric element 4A is configured so that eight waves of bending vibration can be generated most efficiently.

Further, since the position of the longitudinal vibrator 12A relative to the bending vibrator 10A is the position of the node of the bending vibration having the same phase, the voltage signals applied to each longitudinal vibrator 12A may be in the same phase. Although the number of longitudinal vibrators 12A provided is four in this embodiment, the number may be further increased. Vertical vibrator 12
The maximum number of A that can be arranged is 16, which is the same as the number of bending vibration nodes.
The number of waves is twice the wave number of bending vibration. Also,
Regarding the number and position of the support pins, they do not necessarily need to be provided at the nodes where the longitudinal vibrators are arranged, and may be provided at any position as long as the nodes of bending vibration.

Furthermore, as the number of vertical oscillators increases, the force of vibration in the vertical direction increases,
The driving force of the motor can be increased.

4(A)(B) and FIG. 5(A)(B) respectively show modified examples of the driving body 15 in the ultrasonic motor of the present invention. FIG. 5(A) is a plan view of the driving bodies 15B and 15C, and FIG. 4(B) and FIG. 5(B) respectively show their side faces.

The driving body 15B shown in FIGS. 4(A) and 4(B) has an elastic body 5B and a piezoelectric element 4B constituting the bending vibrator 10B, which are formed to have an elliptical planar shape, and are positioned at equal intervals on the upper surface. Four vertical vibrators 12B are arranged, and the fifth
The driving body 15C in FIGS. (A) and (B) has an elastic body 5C and a piezoelectric element 4C forming the bending vibrator 10C so that the planar shape is an annular quadrangle, and the driving body 15C is positioned at equal intervals on the upper surface. Vertical vibrators 12C are arranged at four locations.

In this way, the shape of the bending vibrator may be an ellipse, a square, or any other shape as long as the neutral plane of the bend has a closed curve.

However, if the closed curve has a singular point or a point where the curvature is significantly different from other points, the transmission efficiency of bending vibration will decrease, so it is better to form the curve as smoothly as possible. For example, as shown in Figure 5. As shown in (A), the four corners of the four corners are connected by circular arcs.

FIG. 6 shows a third embodiment of the present invention. The difference between this third embodiment and the first embodiment is that in the first embodiment, the drive body 15 was fixed, but in this embodiment, the drive body 15D and the fixed frame IA are fixed relative to the base 16. It is designed to be driven. That is, the elastic body 5
D, a bending vibrator 10D consisting of a piezoelectric cord 4D is placed in contact with a base 16 with vertical vibrators 12D disposed at three equal positions on the lower surface of the elastic body 5D, and the vertical vibrator 12D of the elastic body 5D is The support pins attached to the corresponding positions are attached to the support body 14D.
The fixing frame 1 is coated with a fitting notch 1e of [A] and is covered with a fixed frame disposed on the drive body 15D with this support pin.
The driving body 15D is pressed onto the base 16 by its own weight.

With this configuration, an elastic member for compression such as a leaf spring is not required, and the structure becomes extremely simple. Moreover, the bending vibration of the bending vibrator 10D is set to a constant amplitude, and the three longitudinal vibrators 12
By controlling at least one of the phase shift and amplitude of the bending vibration of D, the driver 15D can be rotated relative to the base 16 as shown in FIG.
It can move freely in three directions of movement.

[Effects of the Invention] As described above, according to the present invention, since the bending vibrator has an endless closed curve shape, the bending vibration generation efficiency is high, and the efficiency of the motor can be improved. For this reason, with conventional annular ultrasonic motors, it was difficult to create a highly efficient motor with a shape other than an annular shape.However, in the present invention, standing waves of bending vibration are generated on a closed curve. Once the conditions are met, a highly efficient hollow ultrasonic motor can be manufactured relatively easily.

In addition, a bending vibrator can be made into any shape as long as it has a closed curve shape, and since a bending vibrator generates standing wave bending vibration, it is necessary to support the position of the bending vibration node. , it is possible to realize a highly efficient motor without impairing the efficiency of the ultrasonic motor. In addition, it has a bending vibrator and a longitudinal vibrator so that the bending vibration that generates rotational driving force and the longitudinal vibration that presses the driven member can be generated independently, so it is remarkable that the driven member can be controlled stably. It is also effective.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of an ultrasonic motor showing a first embodiment of the present invention. FIG. 2 is an enlarged sectional view of the left half of the ultrasonic motor shown in FIG. 1. FIG. FIGS. 4(A) and 4(B) are a perspective view showing only the driving body in an ultrasonic motor according to a second embodiment of the invention; )(B) is a plan view and a side view when the driving body is made into a rectangular shape, and FIG. 6 is an exploded perspective view of an ultrasonic motor showing a third embodiment of the present invention. 4.4A, 4B, 4C, 4D...Piezoelectric element (electro-mechanical conversion element) 5.5A, 5B, 5C, 5D...Elastic body 7... ...Rotor (driven member) 10, IO
A, IOB, IOC, IOD...Bending vibrator 12.12A, 12B, 12C, 12D...
・Longitudinal oscillator

Claims (1)

[Claims] (1) Consisting of an annular elastic body and a plurality of electro-mechanical conversion elements fixed to the elastic body, by applying an alternating current voltage to the electro-mechanical conversion elements, a bending vibrator that generates a standing wave type bending vibration; and a bending vibrator that is provided on the surface of the elastic body on a nodal line of the bending vibration, is oscillated about the nodal line by the bending vibration, and generates an AC voltage. a vertical vibrator that expands and contracts in the amplitude direction of the bending vibration when the bending vibration is applied; and a driven member that is pressed against the tip end surface of the vertical vibrator, and An ultrasonic motor characterized in that the driven member is moved relative to the bending vibrator and the longitudinal vibrator in the wavelength direction of the bending vibrator by expanding and contracting the longitudinal vibrator.