JPH01278271A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To increase a torque by employing a bolt-clamped Langevin type twist vibrator as a stator. CONSTITUTION:An ultrasonic motor has a bolt-clamped Langevin type twist vibrator 10, and ring-like piezoelectric elements 11a--11d, and metal blocks 12a-12b, etc. A bearing type slide element 17 is disposed at the inner part of a rotor 16, and the motor is composed of a ringlike laminated piezoelectric actuator 19, a washer 20, etc. A light-weight and highly rigid material such as aluminium alloy, Ti alloy, etc., is used as the block 12a of the blocks 12a-12b for forming a twist vibrator 10 in contact with the rotor 16, and a material having relatively large specific weight and large rigidity such as Cu, brass is used as the block 12b. Thus, the amplitude of the twisting vibration becomes maximum at the upper end face of the block 12a, and the rotating speed of the rotor 16 is accelerated.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is an ultrasonic device that excites ultrasonic vibrations in a piezoelectric vibrator, which is a stator, and rotates a rotor pressed against the piezoelectric vibrator through frictional force. It concerns a sonic motor.

(Prior technology) An ultrasonic motor is a motor based on a new principle that obtains rotational force through ultrasonic vibration.
Compared to conventional electromagnetic motors, it has completely different characteristics such as low speed and high torque. In other words, the torque per unit volume is extremely large, and when used at low speeds, gearless and brakeless systems are possible.Furthermore, the inertial mass is small.
The static holding force of the rotor is also large, so it has the advantage of excellent responsiveness.

Various ultrasonic motors have been proposed so far, but traveling wave ultrasonic motors that can easily switch the rotational direction have been proposed in Japanese Patent Application Laid-open Nos. 58-148682 and 59-1989.
No. 96881 and Japanese Patent Application Laid-open No. 59-96882, the research has been vigorously conducted. On the other hand, the research and development of a bolt-fastened Langevin vibrator that can output high torsional vibration energy using an annular zirconium lead titanate piezoelectric ceramic as an active element was already conducted in Japan in 1972 by Nemoto, Mori et al. It is reported in detail in the Journal of the Acoustical Society of Japan, Vol. 28, No. 7, pp. 117-126. In addition, regarding active elements, construction methods, and manufacturing methods applicable to the torsional oscillator,
May 1976, Lecture Papers of the Acoustical Society of Japan pp, 395-396, by Tomiyoshi Roof, [Analysis of Ceramic Torsion Transducer], October 1972, Lecture Papers of the Acoustical Society of Japan pp, 319-320, Nemoto Mori. , Morihiro and Kogure published the title [Torsional oscillator using piezoelectric ceramics (January).
Various configurations have been proposed as disclosed in Publication No. 4.

(Problems to be Solved by the Invention) Traveling wave ultrasonic motors utilize the deflection vibration that occurs around the circumference of a stator, which is made of a disk elastic body and a piezoelectric ceramic plate. Waves are excited using a two-phase or multi-phase drive method to rotate rotors that are pressed against each other. However, since these traveling wave ultrasonic motors use a bending traveling wave, the stator has a large compliance when viewed from the rotor. For this reason, while it is relatively easy to obtain a medium driving force,
High driving force (for example, 1 kgf-cm of torque with a diameter of 2 cm)
above) was difficult to obtain. Further, since the bending traveling wave type ultrasonic motor generates driving force only through resonance, there is a drawback that there is little freedom in design.

An object of the present invention is to realize an ultrasonic motor that can eliminate the above-mentioned drawbacks by using a bolted Langevin type plate hearing vibrator as a stator.

(Means for Solving the Problems) As shown in FIG. 1, the ultrasonic motor of the present invention is composed of a bolted Langevin type plate helical vibrator as a stator, a laminated piezoelectric actuator, and a rotor. The rotor is always statically pressed under constant pressure between the laminated piezoelectric actuator and the bolted Langevin-type plate torsional oscillator, and the metal block portion of the torsional oscillator that comes into contact with the rotor A structural material that is lightweight and has high rigidity is used, and a structural material that has a high specific gravity and high rigidity is used for the metal block portion of the torsion oscillator that is remote from the rotor. The laminated piezoelectric actuator is non-resonant, and the bolted Langevin-type plate hear vibrator is independently driven in a resonant mode.

(Function) The piezoelectric actuator used in the ultrasonic motor of the present invention is disclosed in Japanese Patent Application Laid-Open Nos. 57-79035 and 57-79036.
As shown in the above publication, it has multilayer internal electrodes (distance between electrodes is 30 pm to 200 pm) and can be manufactured using laminated ceramic technology. This actuator operates with a longitudinal effect that has an extremely high electromechanical conversion efficiency, and it is possible to obtain a large electrostrictive effect with a low voltage. Although the torsional oscillator is driven in a resonant mode, the actuator is excited non-resonantly in a manner that matches the resonant frequency of the torsional oscillator.

Therefore, the dimensions of the torsional vibrator must be determined in advance at the design stage in order to match the desired resonance frequency, but since the actuator is operated in a non-resonant manner, there are no particular restrictions on the dimensions. However, as is well known, the higher the height of the actuator, the greater the total longitudinal vibration displacement.

Therefore, when determining the driving frequency of an ultrasonic motor, it is only necessary to determine the resonant frequency of the torsional oscillator, making the design significantly simpler than that of conventional traveling wave ultrasonic motors. The degree of freedom will also increase. Also,
As is well known in the operation of the transducer part of a mechanical channel filter that uses torsional mode, the torsional oscillator operates in a mode by torsional deformation of a round bar, similar to the movement of wringing a rag. In other words, the torsional vibration wave emitted from the piezoelectric element, which is the source of torsional vibration, propagates to the two metal blocks that sandwich the piezoelectric element at both ends, and resonates at a half wavelength at the resonant frequency fr. cause As is well known, this half wavelength resonance mode has a larger torsional amplitude as it approaches both end faces of the two metal blocks. In the present invention, one of the two metal blocks constituting the torsional oscillator is made to have a larger specific gravity, and a wavelength mode vibration node is provided at the part where the metal block with the larger specific gravity contacts the piezoelectric element. It has a structure in which the support plate is taken out at the joint. Therefore, this torsional oscillator alternately generates rotational force in the clockwise and counterclockwise directions at the resonance frequency fr. By bringing the larger one into contact with the support plate side, a larger output can be produced due to stable support.

Here, the case of rotating the rotor will be described. First, let's talk about counterclockwise rotation. When the bolted Langevin plate torsional vibrator applies counterclockwise rotational force to the rotor, the surface of the torsional vibrator that contacts the rotor deforms counterclockwise, the laminated piezoelectric actuator torsively vibrates. A voltage is applied from another power source so that the child stretches and deforms in the axial direction in synchronization with the movement of the child, and the rotor and torsion oscillator are momentarily and strongly pressed together. At this time, the rotor can obtain a large rotational force in the counterclockwise direction through the frictional force. Furthermore, when the surface of the torsional vibrator that contacts the rotor rotates clockwise, the laminated piezoelectric actuator contracts in the axial direction.
The pressure contact force between the rotor and the torsional oscillator is temporally reduced to zero, and the clutch is activated to prevent the clockwise motion of the torsional oscillator from being transmitted to the rotor. Therefore, in this case, the rotor can smoothly rotate counterclockwise by a series of operations of the torsional vibrator and the piezoelectric actuator.

On the other hand, when the rotor is rotated clockwise, the torsional oscillator is simply excited at the resonant frequency, and the piezoelectric actuator that performs the clutch operation is rotated 180 degrees. In this case, too, the rotor can rotate smoothly clockwise in which only the phase needs to be changed to make the phases different.

(Example) Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of an ultrasonic motor that is an embodiment of the present invention. In Fig. 1, section 10 shows a bolted Langevin-type plate oscillator, lla, llb.

11c and lid are ring-shaped piezoelectric elements made of, for example, lead zirconium titanate ceramic, and are polarized in the circumferential direction. These piezoelectric elements are firmly bonded with an epoxy adhesive or solder via an electrode plate made of Cu, etc., and the pair of lla and llc is llb,
The pair of lids is polarized in opposite directions. For example, if the pair lla, lie is polarized clockwise, the pair llb, lid is polarized counterclockwise. Moreover, the piezoelectric elements 11a, llb, lie, li
d, electrodes are applied on the upper and lower surfaces by a method such as sputtering, plating, or vapor deposition, and electrical terminals are taken out in parallel. Therefore, based on the principle of the torsional oscillator disclosed in Japanese Patent Publication No. 39-5864, the polarization directions of adjacent piezoelectric elements are opposite to each other in a torsional vibration conversion portion made up of more layers of piezoelectric elements.

12a and 12b are metal blocks, and static pressure is applied to piezoelectric elements 11a and 11 by bolts 13a and nuts 14.
b, llc.

It is applied to the lid part. Further, 15 is a disc spring, which is arranged to minimize changes in the pressure applied to the piezoelectric element due to temperature changes due to differences in the coefficient of thermal expansion of each member constituting the torsional vibrator 10. It is something. 16
is a rotor, and a bearing type sliding element 17 having a small coefficient of friction is disposed inside the rotor. 19 is a ring-shaped laminated piezoelectric actuator, and 20 is a pedestal. In order to enable the ultrasonic motor to operate, the piezoelectric actuator 19, rotor 16 and torsion oscillator 10 must be connected when not in operation.
must be pressed together with strong static pressure.

The bolt 13b, the spring 22, and the nut 21 constitute static pressure applying means, and the bearing type sliding element 18 is provided so that the piezoelectric actuator element 19 does not rotate together when the rotor 16 rotates. be.

With such a structure, of the metal blocks 12a and 12b constituting the torsional oscillator, the metal block 12a that comes into contact with the rotor 16 is made of a lightweight and highly rigid structural material such as A1 alloy or Ti alloy, and is For the separate metal block 12b, a structural material with high specific gravity and high rigidity, such as Cu, brass, or steel alloy, is used.

Furthermore, a metal block 12b with a larger specific gravity and a piezoelectric element 11
d, and the support plate is taken out from the node of the torsional vibration wave resonance mode.

As a result, the amplitude due to torsional vibration is reduced by the metal block 12.
It is maximum at the upper end surface of a, increasing the rotational speed of the rotor, and also making it easy to support and fix, resulting in an ultrasonic motor with little vibration energy dissipated by the support.

Further, in the ultrasonic motor of this configuration, the piezoelectric element 11a is the part where different members are bonded together using an adhesive.

11b, lie, and lid portions, and this bonded portion has extremely high mechanical strength because strong static compressive bias stress is constantly applied thereto. Since no adhesive is used in the other parts, the structure has the advantage of high mechanical strength.

In the ultrasonic motor of this configuration, the piezoelectric actuator 1
9 is connected to an oscillator and an amplifier through a phase shifter that allows the phase of the drive voltage to be freely changed, and the oscillator is common and only the amplifiers are different to form ring-shaped piezoelectric elements 11a, llb,
llc, connect to electrical terminals 23 and 24 coming out of the lid. When the rotor 16 is rotated counterclockwise, the piezoelectric actuator 19 is expanded in synchronization with the top surface of the torsion vibrator 10 being twisted counterclockwise.

At this time, the rotor receives a counterclockwise rotational force through the frictional force of the torsional oscillator 10. In addition, the torsion oscillator 10
If the top surface of rotates clockwise in the next half cycle,
By contracting the piezoelectric actuator, the pressure force between the torsional vibrator 10 and the rotor 16 can be reduced to almost zero. Further, when the rotor 16 is rotated clockwise, the phase of the piezoelectric actuator is further advanced by 180 degrees, contrary to the above explanation, and the top surface of the torsion vibrator 10 is rotated clockwise, and the piezoelectric actuator 19 is rotated clockwise. All you have to do is change the phase so that it expands. This piezoelectric actuator can be driven using an alternating current wave or a pulse wave. This is a privilege of piezoelectric actuators that operate off-resonance.

FIG. 2 shows another embodiment of the invention. This uses a pedestal 25 with a protrusion in place of the bearing sliding element 18 shown in FIG. The innermost portion of the bearing sliding element disposed inside the rotor 16 is connected to the rotor 126.
Even if the pedestal 25 rotates, it hardly rotates due to its structure, so the protruding portion of the pedestal 25 is brought into contact with this portion. Even in such a structure, performance similar to that of the ultrasonic motor shown in FIG. 1 can be obtained, and a simple structure can be realized.

(Effects of the Invention) As described above, the present invention provides an ultrasonic motor consisting of a stator consisting of a torsion vibrator and a piezoelectric actuator as non-rotating parts, and a rotor that rotates. (1) Direction of rotation It is possible to realize an ultrasonic motor that can move in both forward and reverse directions and has a large torque.

(2) Since the piezoelectric actuator operates in a non-resonant manner, the driving frequency of the ultrasonic motor is largely determined by the resonant frequency of the torsional vibrator, making the design easy and easy to design. There is also a lot of freedom.

(3) The ultrasonic motor according to the present invention is extremely mechanically robust because the bonding point is limited to the piezoelectric element part of the torsional vibrator and this part is subjected to large static compressive device stress. Yes, it is easy to manufacture.

(4) The torsional oscillator can be supported and fixed, and of the two metal blocks that make up the torsional oscillator, the vibration amplitude of the metal block that comes into contact with the rotor is larger, so it is easier to fix and has a large rotational output. An ultrasonic motor is obtained.

It has excellent effects.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of an ultrasonic motor showing an embodiment of the present invention. Each symbol in the figure indicates the following content. 10.1. Bolt-fastened Langevin type plate oscillator, 1
1a. 11b, lie, lid... piezoelectric element for torsional mode excitation, 12a. 12v...metal block, 13a, 13b...bolt, 14°21...nut, 15...disc spring, 16
...Rotor, 17.18...Bearing sliding element,
19... Laminated piezoelectric actuator, 20... Pedestal,
21... Spring, 23.24... Electrical terminal, 25...
・Pedestal with protrusions.

Claims (1)

[Claims] An ultrasonic motor that generates rotational energy in a rotor by using the vibration energy of a vibrator through frictional force is composed of a bolted Langevin-type torsional vibrator as a stator, a laminated piezoelectric actuator, and a rotor, and the rotor is composed of a bolted Langevin type torsion vibrator as a stator, a laminated piezoelectric actuator, and a rotor. A lightweight metal block is placed between the actuator and the bolted Langevin-type torsional oscillator while being statically in contact with a constant pressure. A structural material with high rigidity is used, and a structural material with high specific gravity and high rigidity is used for the metal block portion of the torsional oscillator remote from the rotor, and the laminated piezoelectric actuator is non-resonant and An ultrasonic motor characterized in that a Langevin-type torsional vibrator is independently driven in a resonance mode.