JPH01174281A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To stably perform a control by mounting a vibrating sensor to a stator, serving as the vibrating bar, respectively in its two or more side surfaces positioned next to each other and feeding back an output signal of the sensor by a control circuit. CONSTITUTION:An ultrasonic motor is provided with electric-mechanical energy converter elements 2 adhesively mounted by pressure respectively to four sides of a stator main unit 1 serving as the vibrating bar, and of these elements, the ultrasonic motor provides the elements 2A, 2B for excitation respectively in vertical and horizontal directions and the elements 2C, 2D as the vibration sensor for detecting vibration respectively in vertical and horizontal directions. A control circuit of the ultrasonic motor is constituted of an oscillator 3 of alternate feed voltage for the converter elements 2A, 2B, phase shifter 4, resonance point follow-up circuit 7, amplitude follow-up circuits 8-9 and a phase follow-up circuit 10. And by these four follow-up circuits 7-10 separately acting respectively, the stator main unit 1 holds its vibrative condition. Thus even for disturbance and dispersion of the characteristic of the vibrating bar, a feedback is performed so as to obtain the fixed vibrative condition.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an ultrasonic motor that generates mechanical power without relying on electromagnetic force, and is particularly applicable to small portable devices such as cameras. The present invention relates to a small and lightweight ultrasonic motor suitable for use in the following applications.

[Prior Art] Various types of rotary power generators, which are motors in a broad sense, are known depending on the principle of power generation, but electric motors, which generate mechanical rotational force using electromagnetic force, are the most compact. Because of its high practicality, this motor is known as a motor in a narrow sense.

Due to recent technological advances, electric motors have become extremely compact, so small electric motors are now installed in various small portable devices such as cameras, and these motors are used to improve the performance of these devices. contributes to

However, although the small electric motors installed in cameras and the like can rotate at high speeds, they cannot generate large torque at low speeds, so a reduction mechanism is required. There is a drawback that the volume of the power generating device including the motor and the speed reduction mechanism becomes considerably large. Therefore, there has been a desire to develop a motor that is small and lightweight, can generate large torque at low speeds, and does not require a speed reduction mechanism.

Against this background, in recent years, attempts have been made to use electro-mechanical energy conversion elements as power generation sources. Ultrasonic motors have recently been developed.

This known ultrasonic motor has a toroidal stator and a toroidal rotor, and a progressive elastic surface is applied to the stator by means of an electro-mechanical energy conversion element which is annularly glued to the end face of the stator. It is configured to generate waves, thereby rotating the rotor in contact with the end face of the stator.

This known ultrasonic motor is capable of generating large torque at low speeds, eliminating the need for a deceleration mechanism, and is therefore suitable as an autofocus motor for cameras, etc. However, in this known ultrasonic motor, the stator There has been a problem in that the vibrations generated in the stator are greatly attenuated by supporting and pressurizing the stator, and it is difficult to support and press the stator without damping the vibrations.

Therefore, the applicant has previously filed a patent application filed in 1983-28.
The ultrasonic motor No. 6242 uses a standing wave type vibrator with distinct vibration nodes, making it a much smaller motor than an annular stator, and also features the ability to suppress vibration damping due to support. have.

As shown in FIG. 2, the conventional method of supplying power to the stator in an ultrasonic motor involves four electrical-mechanical energy conversion elements 2 bonded under pressure to the center of the upper and lower surfaces and both side surfaces of the stator body 1. (A), 2 (B), 2 (C
), 2 (D), the two facing conversion elements 2
(A), 2 (C) are one set, and the conversion element 2
(B) and 2 (D) are set as another set, and by adding an alternating voltage of a certain frequency and amplitude to one set, and adding another alternating voltage having a phase difference from the alternating voltage to the other set. , the stator body 1 was excited to cause deflection vibration in two directions.

[Problems to be Solved by the Invention] According to the conventional power supply method for an ultrasonic motor explained in FIG. The main body is in the form of an oven loop, and when some disturbance occurs to the stator main body 1, for example, if a moving object is strongly pressed against the stator main body 1, the resonance frequency of the image in the direction of the push increases, but since the power supply continues without any change in the power supply frequency, alternating voltage range, phase difference, etc., the power supply state deviates from the initially set power supply state that is intended to optimally move the stator body 1. Therefore, there is a problem in that the moving force and moving speed of the moving body in contact with the stator body 1 may become small, or the moving body may stop moving at all. Other disturbances include temperature, humidity, pressing force, and load torque.

In addition, manufacturing errors of the stator body 1 and the electro-mechanical energy conversion elements 2 (A), 2 (B), 2 (C), 2 (D), the stator body 1 and the electric-mechanical energy conversion elements 2 (A), 2
(B), 2 (C), and 2 (D), the characteristics of each stator vary considerably due to the positional accuracy of pressure bonding, variations in adhesive layer thickness, variations in material constants, variations in material quality, etc. This variation causes variations in the frequency and amplitude of the two-way vibration, as well as an inclination in the vibration direction. Therefore, even if the power is supplied in the same way, there is a problem in that the vibrations of the stator body 1 are different from each other.

The present invention aims to solve the above problems.

[Means for Solving the Problems] A movable body, which extends in a direction perpendicular to the direction of movement of the movable body, is temporarily fixed to a stationary member, and whose outer circumferential surface is connected to the outer circumferential surface of the movable body or One or more vibrating rods disposed close to the inner circumferential surface or both surfaces thereof, and vibration excitation means for causing rotational movement at the tip of the vibrating rod in a plane orthogonal to the moving direction of the moving body. In an ultrasonic motor provided on two or more sides of the vibrating rod, two adjacent sides of the vibrating rod
The vibration sensor has three or more vibration sensors attached to each side, and a control circuit that controls a signal applied to the vibration excitation means based on an output signal from the vibration sensor.

[Function] According to the present invention, instead of using the conventional open-loop power supply system, the vibration state of the vibrating rod is detected by a vibration sensor, and the vibration state is maintained even in response to disturbances and variations in the characteristics of the vibrating rod. By feeding back the signal from the sensor and using a closed-loop control system for power supply, a stable output can be obtained as an ultrasonic motor.

[Implementation example] FIG. 1 shows a first embodiment of the invention.

In FIG. 1, reference numeral 1 denotes a stator body which is a vibrating rod, and this stator body 1 is shown in a cross section along the cutting line A-A'' in FIG.

Also 2 (A), 2 (B), 2 (C), 2 (D)
denotes a wealth-mechanical energy conversion element which is bonded under pressure to each of the four sides of the stator body 1, and among these, the conversion element 2(A) is provided to excite the stator body 1 in the vertical direction. The conversion element 2 (B) is also provided for horizontal excitation. Further, the conversion element 2 (C) is provided as a vibration sensor for detecting vertical vibration of the stator main body 1,
The conversion element 2 (D) is also provided as a vibration sensor for detecting horizontal direction imaging. and the conversion element 2 (C) when the stator body 1 is vibrating;
The amplitude of the sensor output alternating voltage of 2 (D) is proportional to the amplitude of the vibration of the stator body 1.

Further, 3 is an oscillator that generates an element of the alternating voltage to be fed to the conversion elements 2 (A) and 2 (B), 4 is a phase shifter that changes the phase difference of the alternating voltage of the oscillator 3, and 5 and 6. are an amplifier (A) and an amplifier (B) for increasing the amplitude of the alternating voltage from the oscillator 3 or phase shifter 4;
The amplified alternating voltages are respectively transferred to the conversion element 2 (8)
, 2 (B). 7 determines the resonance point of vertical vibration (or horizontal vibration) from the output of the amplifier 5 (or amplifier 6) and the output of the conversion element 2 (C) (or conversion element 2 (D)) as a vibration sensor. A resonance point tracking circuit for determining and controlling the oscillation frequency of the connected oscillator 3;
An amplitude follow-up circuit (8) compares whether the set amplitude is reached and controls the connected amplifier 5 based on its output; 9 is an amplitude follow-up circuit 8 for horizontal vibration;
An amplitude tracking circuit (B), 10 having the same function as the conversion element 2(C), 2(D) as a vibration sensor
This is a phase tracking circuit that detects the phase difference between two signals obtained from J and controls the connected phase shifter 4.

In an ultrasonic motor having a circuit as shown in Fig. 1, the operating principle is the same as that of a conventional ultrasonic motor, so an explanation of the principle will be omitted.
The operation will be explained with reference to the figure and FIG.

Here, consider a stator that exhibits frequency characteristics as shown in FIG. 3, and consider that the imaging locus of the stator is circular.

In FIG. 3, curve A represents the amplitude of vertical vibration of the stator, and curve B represents the amplitude of horizontal vibration. Curves C and D represent the amplifier 5.6 and the conversion element 2 (C) as a sensor, respectively.

2(D). Here, the vibrations in the vertical direction and the horizontal direction have a difference in resonance frequency and amplitude due to disturbance.

First, an alternating voltage of a certain frequency is generated from the oscillator 3,
The alternating voltage is transmitted through a phase shifter 4, an amplifier (8) 5, an amplifier (B
) 6 to drive the stator body 1.
(A) and 2 (B), and the stator body 1 begins to flexurally vibrate in two directions. Due to this amplitude, the conversion element 2 (C) as a vibration sensor outputs the vertical vibration as an alternating voltage, and the signal and the output of the amplifier (8) 5 are inputted to the resonance point tracking circuit 7 . At the resonance point in the vertical direction, for the alternating voltage applied to the conversion element 2 (A),
Since the phase of the alternating voltage output from the conversion element 2 (C) as a sensor is delayed by 90', the frequency at the intersection of the curve C and the 190° line in FIG. 3 is the resonance frequency, and the resonance point tracking circuit In step 7, find this resonant frequency and select the connected oscillator 3.
control so that it oscillates at the resonant frequency. and,
In order to make the vibration locus circular, it is necessary to match the amplitudes of the vibrations in the vertical and horizontal directions. First, set the volume of the desired amplitude using variable resistors 11 and 12.
The conversion element 2 (C), 2 ([1
) The amplifier (A) 5 and the amplifier (B) 6 are controlled so that the amplitude of the output alternating voltage of the stator body 1 corresponds to the desired amplitude in the vertical and horizontal directions of the stator body 1.

In the case of FIG. 3, the volume is set by the variable resistor 12 so that the horizontal amplitude matches the vertical amplitude, and the amplifier (B) 6 is controlled by the amplitude tracking circuit (B) 9 to increase the amplification factor. ing. As a result, curve B is curve B
', and the vibration amplitudes in both directions are equal on the resonant frequency of vertical vibration. However, at this time, the phase difference between the output alternating voltages of the conversion elements 2 ([:), 2 (D) as sensors is not 90°, but often exhibits inclined circular vibration. Therefore, the volume is set to 90° using the variable resistor 13, and the phase difference tracking circuit 10 operates by looking at the output of the conversion element 2 ((:), 2 (D) as a sensor, and controls the Mu/Japanese language 4. However, the phase difference between the output alternating voltages of the conversion elements 2(C) and 2(D) as sensors is 90°, that is, circular vibration is made.

As described above, the resonance point tracking circuit 7, the amplitude tracking circuit (A)
8, amplitude tracking circuit (B) 9, and phase difference tracking circuit 10 each work independently to maintain the vibration state of the stator body 1.

Note that the vibration form is not limited to circular, but can be arbitrary, and the variable resistor 11
, 12.13.

The four tracking circuits are always trying to track,
They are not easily affected by external disturbances, and variations in vibration due to individual differences in the stator body 10 are also absorbed within these circuit configurations.

Note that the resonance point tracking circuit 7 may use human power for the output of the amplifier (8) 6 and the output of the conversion element 2 (D) as a sensor. In that case, it becomes a resonance point tracking circuit with horizontal amplitude.

Furthermore, in the first embodiment, there are two electric-mechanical energy conversion elements 2 (A) and 2 (B) for driving, which is half the number of electric-mechanical energy conversion elements 2 (A) and 2 (B) compared to the four elements of the conventional device shown in FIG. As a result, the input of human power is halved, and the output power is also roughly halved.

Therefore, FIGS. 4 and 5 show an example in which the number of electric-mechanical energy conversion elements for driving is four as in the conventional case, and in addition, a vibration sensor is attached.

That is, FIG. 4 shows a second embodiment of the invention, and FIG. 5 shows a third embodiment of the invention.

In FIG. 4, electric-mechanical energy conversion element 2 (A)
, 2 (B), 2 (C), and 2 (D) are used for driving,
On both sides of the conversion elements 2 (8) and 2 (B), vibration nodes a,
A vertical vibration sensor 14 and a horizontal vibration sensor 15 are pasted to such an extent that they do not interfere with the support of b. As shown in FIG. 4, the driving conversion elements 2 (A), 2 (B),
2 (C) and 2 (D), the same force as the conventional one can be extracted, and the vibration can be controlled using the circuit shown in FIG.

In FIG. 5, in order to increase the output of the vertical vibration sensor 14 and the horizontal vibration sensor 15, the sensor 14.1 is
5, and the sensors 14 and 15 are mounted at the central position where the curvature is the largest among the vibrations of the data body 1. In this case, the sensors 14 and 15 are glued onto the conversion elements 2 (A) and 2 (B) via an insulating plate 16. By doing so, a larger sensor output can be obtained than in the case of FIG. 4, an amplification circuit for the sensor output in the control circuit is not required, and the configuration of the control circuit is simplified.

Note that as a vibration sensor, a piezoelectric material may be vapor-deposited and polarized on the surface of the stator body instead of using an electro-mechanical energy conversion element. The size of the vibrating rod is approximately several μm, and the size of the vibrating rod can be made somewhat compact.

[Effects of the Invention] As explained above, according to the present invention, a vibration sensor is attached to each of two or more adjacent sides of a vibrating rod, which is a stator, and the output signal of the sensor is observed. By knowing the vibration state and feeding back the output signal through the control circuit, any desired vibration form can be kept constant without the influence of external disturbances, and variations in vibration form due to individual differences in the stator etc. can be absorbed and any desired vibration form can be achieved. The vibration form can be maintained. As a result, a stable vibration form can be obtained, that is, a stable mechanical output can be obtained from the moving body in contact with the stator.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the first embodiment of the present invention, Fig. 2 is a front view showing an example of the conventional technology, and Fig. 3 shows the relationship between the stator drive frequency, vibration amplitude, and phase difference. FIG. 4 is an explanatory diagram showing the second embodiment of the present invention, and FIG. 5 is an explanatory diagram showing the second embodiment of the present invention.
The figure is also an explanatory diagram showing the third embodiment. 1... Stator body 2 (A), 2 (B), 2 (C), 2 (D)
... Electrical-mechanical energy conversion element 3 ... Oscillator 4 ... Phase shifter 5.6 ...
Amplifier 7...Resonance point tracking circuit 8.9...Amplitude tracking circuit 10...Phase difference tracking circuit 14.15...Vibration sensor Figure 2 Figure 3

Claims (1)

[Claims] a movable body, which extends in a direction perpendicular to the direction of movement of the movable body, is temporarily fixed to a stationary member, and has an outer circumferential surface close to at least one of the outer circumferential surface and the inner circumferential surface of the movable body; a suitable number of vibrating rods, and vibration excitation means for generating rotational movement at the tips of the vibrating rods in a plane perpendicular to the moving direction of the moving body, on two or more of the vibrating rods. In the ultrasonic motor provided on the side surface of the vibrating rod, a vibration sensor is attached to each of two or more adjacent side surfaces of the vibrating rod, and a signal applied to the vibration excitation means is controlled by an output signal from the vibration sensor. An ultrasonic motor comprising a control circuit.