JPH02151279A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To obtain an efficient rotary drive with high capacity at a high speed by disposing a telescopic piezoelectric element at a lever ratio by a lever arm, and symmetrically arranging a plurality of drive sources in which movable strokes are increased. CONSTITUTION:A lever arm 3 is brought into contact with the movable end of a piezoelectric element 4, a predetermined prepressure is applied to integrally mount the other ends of the lever arm 3, the piezoelectric element 4 at mounting fittings 5 by bolts 6, 7. A rotary drum 1 is pressed by the lateral deflection vibration of the lever are 3, and so disposed at a predetermined angle theta and a gap delta as to unidirectionally rotate by a frictional force. The movable stroke of the telescopic piezoelectric element 4 is several mum, but amplified to hundreds of mum by the lever ratio of the lever arm 3 and resonance effect, and converted to a rotatable drive. One piezoelectric element 4 has, for example, 20mmu of diameter, power source E=200V, f=40kHz is applied, approx. 100mum of movable stroke and approx. 20kg of maximum force are obtained. A plurality of drive units of the piezoelectric element 4 are disposed on the periphery of the drum 1 to obtain a rotary force of large capacity at a high speed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the principle of rotation of an ultrasonic motor that uses ultrasonic waves, and uses a piezoelectric element that moves in an elastic manner as a drive source to drive the circular motion of a single rotating drum. Expandable piezoelectric elements are arranged around the circumference with a lever arm to provide a lever ratio so that rotation in both left and right directions can be obtained arbitrarily, and multiple drive sources with expanded movable strokes are arranged symmetrically to achieve high speed and high capacity. This relates to an ultrasonic motor that can provide efficient rotational drive. [Prior art] An example of an ultrasonic motor using a conventional piezoelectric element is:
It is shown in FIG.

FIG. 4 is a perspective view showing an example of a conventional ultrasonic motor, in which a diaphragm 15 is fixed to the top of a ring-shaped piezoelectric body 14, and these are attached to a case 9. Further, the circular plate surface of the rotating disk 8 is brought into close contact with the disk surface of the diaphragm 15, and the disc spring 13 is pressed against the side surface of the rotating disk 8 so as to strongly press this surface. Fixing pin 1
2 and the like are integrally rotatably attached to the fence 10, and electric wires 11 are further connected to the piezoelectric body 14 to integrally construct an ultrasonic motor.

In the ultrasonic motor configured as described above, when a DC source is supplied in pulses from the electric wire 11, the piezoelectric body 14 is divided into a plurality of circular rings, and the polarity operation is alternately arranged next to each other. Therefore, each ring-shaped element portion expands and contracts in the thickness direction. Since the diaphragm 15 is fixed to this surface, it is displaced integrally, and this expanding and contracting frequency and the diaphragm 1
Since the natural vibration frequencies of the circular ring portions 5 are equal, the expansion and contraction vibrations are amplified, and the surface of the diaphragm 15 becomes wavy in the thickness direction due to transverse vibrations, that is, vibrations in the rotational direction of the rotating disk 8. Accompanied by the displacement, a head wave propagates on the plate surface of the circular ring in response to the application of power and rotates.

Since the rotating disk 8 is pressed against this surface, the rotating disk 8 rotates in a direction opposite to the direction of wave propagation due to the frictional action of this pressed portion, that is, the reaction of the rotating disk 8 to the transverse vibration action of the diaphragm 15. The disk 8 rotates.

[Problem that the invention seeks to solve]

However, in the above-described configuration, the speed of the surface wave of the diaphragm 15 moves at a constant speed in the width direction (indicated by W in the figure) with respect to the tangent to the circular ring. However, the displacement angle θ with respect to the axis 10
, the rotation radius R, and the moving distance S of the wave must have the relationship S w R#, but unless the width W of the diaphragm 15 is a line, the rotation radius R is increased by the width W. If there is a difference at the lower limit and the movement of the wave is constant, the displacement angle 0 will always be a different value, and as long as the diaphragm 15 is a rigid body, movement with a different displacement angle θ is not allowed and slips on the width W. The rotating disk 8 moves accordingly.

As a result, rotational torque cannot be obtained effectively, or even if the force on the piezoelectric body 14 side is increased, if the width Wo on the rotating disk 8 side that receives the force is increased, slips and drops will increase as described above. , it is necessary to reduce the width Wo due to heat generation and the like. Of course, even if the friction area is small, increasing the pressing force will increase the friction force, but as the surface pressure increases, the amount of friction on the plate material will increase, so this is not practical, and as a result, only a small capacity can be obtained. , and the efficiency becomes worse. Also, if the radius is increased, the torque will be increased, but with the current technology, it is not possible to increase the torque too much due to problems such as accuracy and stability. In other words, as a result, only small quantities of products are produced,
This has become a big problem.

The common traveling wave types currently on the market are:
Most of them are extremely small, with a capacity of 4 W and a torque T of 4 kg-cm.

The present invention was devised in view of the above-mentioned points, and its purpose is to propose a highly efficient, high-speed, and large-capacity ultrasonic motor.

[Means for solving problems]

In other words, the means to achieve this purpose is to provide a lever arm with lever action and resonance action at the movable tip of a telescoping piezoelectric element, amplify the movable stroke of the piezoelectric element, and use this as a driving source. The rotating drum is arranged so that it rotates in one direction with a required angle θ and gap δ on the circumference of the rotating drum, and these drive sources are arranged symmetrically so that the rotating drum can be rotated arbitrarily left and right. It was constructed by installing multiple locations.

In general, a telescopic piezoelectric element is capable of movable force at a high frequency (several tens of KHz) and has a large driving force (several hundred kgf), but its movable stroke is extremely small, such as a few μm. Even if the circumference of the rotating drum is pressed with this small stroke, it cannot be used as is because it does not reach the minimum stroke determined by manufacturing errors and required gaps of each part. Therefore, in the present invention, a lever arm that acts as a lever is arranged at the movable tip of the piezoelectric element, and the movable stroke of the tip is amplified by the length ratio effect, thereby resonating with the interlocking frequency of the piezoelectric element. Therefore, the amplitude of the correction is increased, and a large stroke, high frequency, and high pressing force are transmitted from the tip of the lever arm to the circumference of the rotating drum. For this reason, rotational drive is performed at extremely high speed, large capacity, and high efficiency.

[For production]

Its operation will be explained in detail in one embodiment described below.

Hereinafter, one embodiment of the present invention will be explained based on the drawings, and the operation will also be explained in detail.

〔Example〕

FIG. 1 is a conceptual diagram of the overall configuration showing one embodiment of the ultrasonic motor of the present invention, FIG. 2 is a conceptual side view of FIG. 1, and FIG.
It is an enlarged view of part A of the figure.

In FIGS. 1 to 3, in an ultrasonic motor using a retractable piezoelectric element 4 as a driving source, a lever arm 3 is attached to the movable tip of the piezoelectric element 4, and a required preload force is applied to this part. The other ends of the lever arm 3 and the piezoelectric element 4 are integrally attached to the mounting bracket 5 with bolts 6.7, and the connecting position of the piezoelectric element 4 and the tip position of the lever arm 3 are set by a required multiple, starting from the fixed end of the lever arm 3. Leverage ratio (L/i in Figures 1 and 3)
), and further arrange the tip of the piezoelectric element 4 on the outer circumference or the inner circumference of the rotating drum 1 so that the natural vibration number of the piezoelectric element 4 and the horizontal natural vibration number of the lever arm 3 are the same number, Rotating drum 1 due to horizontal vibration of lever arm 3
The rotating drum is placed with a required angle θ and gap δ so that it is pressed and rotates in one direction due to frictional force, and the rotating drum is centered around shaft 2 so that the rotating drum can rotate to the left and right on one axis at an angle of 0. The rotary drums 1 are arranged in opposite directions in symmetrical positions, and are arranged at multiple locations facing each other at the same angle θ, so that the rotary drum 1 can rotate freely from side to side, and the shaft 2 is supported by a bearing or the like. However, these are integrated to construct an ultrasonic motor.

In the ultrasonic motor constructed in this way, when obtaining clockwise rotational drive, for example, the 'gL source for left shown in Fig. 1 is OF
When the setting is set to
If the + and - poles of the source are reversed, the lever arm 3 will contract.) The lever arm 3 attached to this movable tip causes a lateral deflection, and the tip expands by a required number of times depending on the lever ratio (L/A). Furthermore, the natural vibration number of this lever arm 3 is the same as the natural vibration number of the piezoelectric element 4, and the pulse-like ON/OFF drive cycle of the '1 source is applied in accordance with this natural vibration number. So,
Due to the resonance amplification of the piezoelectric element 4 and the resonance effect of the lever arm 3, combined with the aforementioned lever ratio (L/1), the tip of the lever arm vibrates extremely greatly. As a result, this starting end, which is disposed on the rotating drum 1 with a slight gap δ, presses against the circumference of the rotating drum 1, and a torque that rotates the rotating drum 1 is generated due to frictional force. Of course, in the return movement of the lever arm 3, by setting the angle θ appropriately, it moves away from the rotating drum 1, and during this time, the rotating drum 1 rotates in the suppression direction due to the moment of inertia of the rotating system, and is subjected to the next period of suppression. .

As described above, this suppression period is driven to match the natural vibration frequency of the pressure 14 element 4, and is generally extremely high, about 20,000 to 50,000 Hz, so that the rotary drum 1 continuously rotates smoothly.

Here, the movable stroke of the telescopic piezoelectric element 4 is several μm, but it is amplified to several hundred μm due to the lever ratio action of the lever arm 3 and the resonance effect, and is converted into rotational drive. For example, in the experimental machine of the present invention, each piezoelectric element 4 has a diameter of 20 mμ.
Power source g=zoov, f=40KH
zwo application L, f: I7- At the tip of arm 3, a movable stroke of about 100 μm and a maximum force of about 20 kg are obtained. Since a plurality of drive units for these piezoelectric elements 4 are arranged around the circumference of the rotary drum 1, a large amount of rotational force can be obtained at high speed.

In addition, the lever arm 3 needs to maintain high fatigue strength and its tip must have excellent wear resistance, so in the experiments of the present invention, the vibration deflection part was made of strong Kerchrome steel, and the tip was made of ceramic. A material with high wear resistance such as
We have achieved practical results by applying hard and wear-resistant surface treatments such as iN (titanium nitride).

Next, when rotating to the left, turn off the useful power source and apply one pulsed high frequency voltage to the power source for counterclockwise rotation, as described above, to obtain counterclockwise rotation. In addition, in order to generate braking torque on the rotating drum 1, a continuous non-pulse pressure of 4 degrees is applied to the left and right sides at the same time, so that the tip of the lever arm 3 presses the outer peripheral surface of the rotating drum 1 and performs braking. The action works. Since this brake torque can be arbitrarily adjusted by the strength of one pressure, it is extremely convenient as an optimal drive source for precise positioning, robot drive, etc. by adjusting the applied frequency and voltage form.

〔Effect of the invention〕

As explained above, according to the present invention, there is no sliding friction movement caused by the radius difference due to the width W of the drive friction surface as in the conventional case, and a linear force is applied to the circumferential surface of the rotary drum 1, resulting in drive efficiency. High durability and long life can be obtained. Furthermore, by increasing the diameter and width of the rotating drum l, and correspondingly increasing the number and driving force of the telescoping piezoelectric elements 4 and lever arms 3, a large capacity can be easily obtained, and even more so than conventional piezoelectric elements. Since the frequency is high, the speed is high, and the driving force is large, so a high capacity can be obtained. Furthermore, if a laminated piezoelectric element is used instead of the telescoping type piezoelectric element 4, a larger movable stroke can be obtained, and the function is exactly the same, but since the number of piezoelectric elements increases, the natural vibration number decreases, making it more economical. The present invention is also improved in this respect.

Furthermore, the conventional one has a capacity of t4W, 1100 at most.
rp was the practical limit, but in the present invention, it is extremely large capacity (for example, 7.5KW) and high speed rotation (for example, 1010KW).
It is practically possible up to 0rp. Furthermore, in the conventional example, a thrust force is applied to the rotating disc 8 by a disc spring 13 in order to obtain a frictional force, so this force is applied to a bearing.

However, in the present invention, the driving source, which is an integral part of the extensible piezoelectric element 4 and the resonator 3, is symmetrically arranged, and the rotation Since the internal forces of the drum 1 cancel each other out, this kind of force is not applied to the shaft 2, resulting in extremely economical and long life.In other words, the ultrasonic motor of the present invention has a high capacity and high efficiency. Furthermore, since the same capacity can be obtained with an extremely small moment of inertia compared to a conventional electric motor, it is useful for a wide variety of practical uses such as labor-saving equipment and robots.

[Brief explanation of the drawing]

FIG. 1 is a conceptual front view of essential parts showing one embodiment of the structure of an ultrasonic motor according to the present invention, FIG. 2 is a conceptual side view of FIG. 1, and FIG.
The figure is an enlarged view of the part A in Fig. 1, and Fig. 4 is a structural diagram of the main parts of an example of a conventional ultrasonic motor. 3...
... Lever arm, 4 ... Piezoelectric element, 5 ...
...Mounting bracket, 6,7...Bolt, 8...
...Rotating disk, 9...Case, 10...
...shaft, 11...electric wire, 12...presser, 13...disc spring, 14...piezoelectric body, 15...・Vibration plate.

Claims (1)

[Claims] In an ultrasonic motor using a telescoping piezoelectric element as a driving source, a lever arm is connected to the movable tip of the piezoelectric element, so that the connecting position of the piezoelectric element and the tip position of the lever arm have a lever ratio of a required multiple. Fix one end of the lever arm, use the fixed end as the starting point, set the natural vibration frequency of the piezoelectric element and the horizontal natural frequency of the lever arm to be the same number, and place the tip of the lever arm on the outer or inner circumference of the rotating drum, on the side of the lever arm. The rotating drum is pressed by the flexural vibration and is arranged with a required angle and gap so that it rotates in one direction, and the angle is changed to
The rotating drums are symmetrically positioned around the axis so that left rotation and right rotation are obtained on one axis, and the rotating drums are oriented in opposite directions to each other.
The rotary drum is integrally configured so that it can rotate in any left or right direction by arranging the angles in the same direction at multiple locations, and receives the expansion and contraction vibration of the piezoelectric element with a lever arm, and the tip of the drum is provided with lever and resonance effects. Vibrate the movable stroke greatly,
An ultrasonic motor characterized in that rotation is obtained by this.