JP2003244974A - Oscillatory wave motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oscillatory wave motor by which driving performance is improved and man-hours for an assembly adjustment are reduced. <P>SOLUTION: The motor includes a vibrator 11, which has a piezoelectric material 13 excited by a driving signal and an elastic body that is joined to the piezoelectric material 13 and that generates a progressive oscillatory wave on a driving surface by the excitation, and a mover which is pressed and put into contact with the driving surface of an elastic body 12 and is driven by the progressive oscillatory wave, wherein the elastic body 12 has a plurality of grooves 12a on the driving surface side. When the average thickness of each groove from the joining face 12e of the piezoelectric material 13 to a groove's bottom 12d of the groove 12a is defined to be tm and a dispersion range of the thickness is defined to be Δt, Δt/tm is arranged to have dispersion of 0.01 or smaller. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration wave motor having an elastic body having a plurality of grooves.

[0002]

2. Description of the Related Art Conventionally, as is known in Japanese Patent Publication No. 17354/1989, this type of vibration wave motor utilizes the expansion and contraction of a piezoelectric body to generate a progressive vibration wave on the drive surface of an elastic body. The traveling wave causes an elliptical motion on the driving surface, and the moving element that is in pressure contact with the wave front of the elliptic motion is driven. Since such a vibration wave motor has a characteristic that it has a high torque even at a low rotation speed, when it is mounted on a drive device, the gear of the drive device can be omitted, so that gear noise is eliminated and positioning accuracy is improved. Can be improved.

A vibrator of a vibration wave motor using such a traveling traveling wave is composed of a piezoelectric body and an elastic body, and the piezoelectric body and the elastic body are firmly adhered by an adhesive or the like. ing. Further, the elastic body is provided with grooves of equal width and substantially equal intervals on the drive surface side opposite to the piezoelectric body joint surface. Due to this groove, the neutral surface of the bending vibration of the elastic body is shifted to the piezoelectric body side, whereby the amplitude of the progressive vibration wave on the drive surface side is expanded.

The progressive vibration wave generated in this elastic body is obtained by synthesizing two standing waves of bending vibration generated by the excitation of the piezoelectric body. The value of the resonance frequency of the standing wave of this bending vibration is, when the order of vibration and the outer and inner diameters are fixed,
It mainly corresponds to the thickness of the elastic body, particularly the groove bottom thickness value of the elastic body. For example, as the groove bottom thickness increases, the resonance frequency of the standing wave of bending vibration increases, and the drive frequency band of the vibration wave motor shifts to a higher frequency accordingly. Further, as the groove bottom thickness becomes thinner, the resonance frequency of the standing wave of bending vibration becomes lower, and accordingly, the driving frequency band of the vibration wave motor shifts to the lower frequency.

Most of the speed control of the vibration wave motor is performed by changing the frequency. In order to perform speed control accurately, it is necessary to inspect and adjust the relationship between speed and frequency such as the frequency of zero speed, the frequency of a certain speed, the frequency of maximum speed, etc. for each motor. Therefore, when the shift amount of the drive frequency band is larger than the individual difference of the vibration wave motor, man-hours are required to find an appropriate drive frequency band.

Further, if the shift amount of the drive frequency band is large, the oscillation unit of the drive circuit may not be able to handle the shift amount. Therefore, it is necessary to prepare several oscillating units having different frequency bands and select the oscillating units according to the shift amount of the bands, which causes a problem that the process becomes complicated. Therefore, it is necessary to suppress the variation in the thickness of the groove bottom and reduce the shift amount of the driving frequency band in order to prevent the increase in the number of steps and the complexity of the process as described above and the increase in the cost. The processing of this groove is usually performed by a milling cutter or a grindstone, and one groove is processed.

[0007]

The progressive vibration wave generated in the elastic body is obtained by combining two standing waves of bending vibration generated by the excitation of the piezoelectric body. In order to obtain a progressive oscillatory wave having a uniform amplitude at any position, it is necessary that the two standing waves have a uniform amplitude distribution shape and substantially the same shape. For example, if there are variations in the thickness of the elastic body,
The amplitude distribution shapes of the two standing waves are distorted and different. In this case, the amplitude of the combined progressive vibration wave may vary depending on the location. On the other hand, the progressive vibration wave is a bending wave, and the phase velocity of the wave is proportional to the thickness. For example, if the thickness of the elastic body varies, the phase velocity of the progressive vibration wave may vary depending on the location. It was expected that the characteristics of the elastic body would be stable if the variations described above were completely eliminated. However, this requires ultra-high precision processing, which inevitably leads to cost increase.

On the other hand, when the elastic body has a variation in shape, the characteristics of the elastic body are not stable, and specifically, there are the following problems. For example, when the thickness of the piezoelectric joint surface from the groove bottom of the elastic body (hereinafter referred to as groove bottom thickness) varies, the amplitude of the progressive vibration wave becomes uneven in the circumferential direction, or the phase The speed is not uniform in the circumferential direction, which deteriorates the driving performance. This has been clarified by an experiment by the present inventor. In particular, according to the experiments conducted by the inventor of the present invention, the frequency-rotation characteristic is deteriorated, and it becomes difficult to drive at low speed (the inclination of the frequency-rotation speed diagram changes).
I understood it. As described above, if the variation in the groove bottom thickness of the elastic body is large within the individual body, there arises a problem that the performance is deteriorated. Also, if the groove bottom thickness varies from individual to individual and the slope of the frequency-rotation speed diagram changes from individual to individual, it becomes necessary to adjust the control parameters for each individual in order to perform speed control with frequency. There is also a problem that the number of man-hours increases.

An object of the present invention is to provide a vibration wave motor having improved drive performance and reduced man-hours for assembly and adjustment.

[0010]

In order to solve the above-mentioned problems, the inventors of the present invention, as a result of diligent research, found the relationship between the variation tendency of the groove bottom thickness and the characteristics of the elastic body, and found the groove bottom thickness. Therefore, the inventors have invented a vibration wave motor capable of obtaining a stable vibrator while preventing the increase in cost without completely eliminating the fluctuation. That is, the invention of claim 1 is a vibrator having a piezoelectric body excited by a drive signal and an elastic body bonded to the piezoelectric body and generating a progressive vibration wave on a drive surface by the excitation; In a vibration wave motor including a moving element that is brought into pressure contact with a driving surface and is driven by the progressive vibration wave, the elastic body has a groove portion on the driving surface side, and The average thickness of each groove up to the groove bottom is tm, and the variation width of the thickness is Δ
The vibration wave motor is characterized in that Δt / tm has a variation of 0.01 or less when defined as t.

According to a second aspect of the present invention, in the vibration wave motor according to the first aspect, the elastic body has a point-symmetric distribution of the variation width and a variation of Δt / tm of 0.01 or less. Is a vibration wave motor.

According to a third aspect of the present invention, in the vibration wave motor according to the first aspect, the elastic body has a random distribution in the variation width, and the variation Δt / tm is 0.01 or less. Is a vibration wave motor.

According to a fourth aspect of the present invention, in the vibration wave motor according to the first aspect, when the elastic body has a partial distribution of the variation width of the thickness in the circumferential direction, Δt / The vibration wave motor is characterized in that tm has a variation of 0.007 or less.

According to a fifth aspect of the present invention, in the vibration wave motor according to the first aspect, the elastic body defines a difference between a thickness of a groove and a thickness of a groove adjacent to the groove as ts. When ts / tm is 0.005 or more, Δt
The vibration wave motor is characterized in that / tm has a variation of 0.007 or less.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a vibration wave motor according to the present invention will be described in detail below with reference to the accompanying drawings. Note that the following embodiments will be described by taking an ultrasonic motor that utilizes the vibration range of ultrasonic waves as an example of the vibration wave motor. FIG. 1 is a diagram illustrating an ultrasonic motor 10 according to an embodiment of the present invention. FIG. 2 is an external perspective view showing the vibrator 11 and the mover 17 of the ultrasonic motor 10 of this embodiment.

The ultrasonic motor 10 of this embodiment is provided with a vibrator 11 and a mover 17, and the vibrator 11 side is fixed,
The moving element (relative movement member) 17 side is rotationally driven. The buffer member 1 is provided below the vibrator 11.
4, the pressure plate 15, the pressure member 16, and the support member 19A are arranged, and the vibration absorbing member 18 and the rotation member 19B are arranged above the moving element 17.

The vibrator 11 includes an elastic body 12 and an elastic body 12
And an electromechanical conversion element (hereinafter, referred to as a piezoelectric body) 13 which is an example of a piezoelectric element or an electrostrictive element for converting electric energy to mechanical energy which will be described later. Although a traveling wave is generated in the vibrating body 11, in the present embodiment, as an example, a traveling wave of nine waves will be described.

The elastic body 12 is made of a metal material having a large resonance sharpness, and its shape is an annular shape. The elastic body 12 has a groove 12a cut on the opposite surface to which the piezoelectric body 13 is bonded, and a protrusion (a portion where the groove 12a is not provided) 1
The front end surface of 2b serves as the drive surface 12c and is brought into pressure contact with the mover 17. The reason for cutting the groove 12a is to bring the neutral surface of the traveling wave closer to the piezoelectric body 13 side as much as possible, thereby amplifying the amplitude of the traveling wave of the driving surface 12c.

The piezoelectric body 13 is divided into two phases (A phase and B phase) along the circumferential direction, and in each phase, 1 /
Elements with alternating polarization for every two wavelengths are arranged,
There is a quarter wavelength interval between the A phase and the B phase.

Below the piezoelectric body 13, a buffer member 14, a pressure plate 15, a pressure member 16 and a support member 19A are arranged. The cushioning member 14 is disposed below the piezoelectric body 13 and is a member for preventing the vibration of the vibrator 11 from being transmitted to the pressure plate 15 and the pressure member 16. For example, a non-woven fabric or felt is used. ing. The pressure plate 15 is a plate for receiving pressure from the pressure member 16. The pressure member 16 is
It is a member that is arranged under the pressure plate 15 and generates a pressing force. In the present embodiment, the pressing member 16 is a disc spring, but a coil spring or a wave spring may be used instead of the disc spring. The support member 19A is the ultrasonic motor 10
Is a member that supports on the fixed side.

The mover 17 is made of a light metal such as aluminum, and the surface of the sliding surface 17a is surface-treated to improve wear resistance. Above this mover 17,
In order to absorb the vibration of the mover 17 in the pressing direction, a vibration absorbing member 18 such as rubber is arranged, on which a rotating member 19B such as a bearing is arranged.

FIG. 3 is a block diagram for explaining the drive control device 20 for the ultrasonic motor according to this embodiment. First,
The configuration of the drive control device 20 for the ultrasonic motor will be described. The drive control device 20 includes an oscillator 21, a controller 22,
The phase shift unit 23, the amplification units 24 and 25, the detection unit 26, and the like are provided.

The oscillator 21 receives a command from the controller 22,
A drive signal having a desired frequency is generated. The phase shift unit 23 divides the drive signal generated by the oscillator 21 into two drive signals having 90 ° different phases. The amplifiers 24 and 25 are the phase shifter 23.
Each of the two drive signals divided by is boosted to a desired voltage. The drive signals from the amplifiers 24 and 25 are
The traveling wave is transmitted to the ultrasonic motor 10 and a traveling wave is generated in the vibrator 11 by the application of this drive signal, and the moving element 17 is driven. The detection unit 26 is composed of an optical linear encoder or the like, and detects the position and speed of a driven body (not shown) driven by driving the moving element 17.

The control unit 22 controls the drive of the ultrasonic motor 10 based on the drive command from the CPU. And
The control unit 22 receives the detection signal from the detection unit 26, obtains position information and speed information based on the value, and controls the frequency of the oscillator 21 so that the oscillator 21 is positioned at the target position.

Next, the operation of the ultrasonic motor drive controller 20 of this embodiment will be described. First, the target position is transmitted to the control unit 22. A drive signal is generated from the oscillating unit 21, the signal is divided into two drive signals having a 90 ° phase difference by the phase shift unit 23, and the amplifying units 24 and 25
It is amplified to the desired voltage. The drive signal is the ultrasonic motor 1
0 is applied to the piezoelectric body 13, the piezoelectric body 13 is excited,
Due to the excitation, a ninth-order bending vibration is generated in the elastic body 12. The piezoelectric body 13 is divided into an A phase and a B phase, and drive signals are applied to the A phase and the B phase, respectively. A
The 9th-order bending vibration generated from the phase and the 9th-order bending vibration generated from the B-phase are such that the positional phases are shifted by ¼ wavelength, and the A-phase drive signal and the B-phase drive signal are different from each other. , 9
Since the phase is 0 ° out of phase, two bending vibrations are combined into nine traveling waves.

The traveling wave has an elliptical motion at its wave front. Therefore, since the moving element 17 is in pressure contact with the driving surface 12c, it is frictionally driven by this elliptic movement. The detection unit 26 is arranged on the driven body driven by the drive of the moving element 17, and the electric pulse signal generated from the detection unit 26 is transmitted to the control unit 22. Control unit 22
Can obtain the current position and the current speed based on this signal, and controls the drive frequency of the oscillator 21 based on the position information, the speed information, and the target position information.

FIG. 4 is a view for explaining the shape of the groove portion of the elastic body of the ultrasonic motor according to this embodiment. Elastic body 12
On the drive surface 12c side, 54 grooves 12a of equal width are provided at equal intervals along the circumferential direction. In the present embodiment, b is defined as the total height of the elastic body 12, and the value t from the joint surface 12e of the piezoelectric body 13 to the groove bottom 12d is defined as the groove bottom thickness. In the present embodiment, when the average groove thickness of the 54 grooves 12a is tm and the variation width of the thickness is Δt,
The Δt / tm was set to have a variation of 0.01 or less. The inventor of the present invention prepared a prototype in which the variation width Δt of the groove bottom thickness t was intentionally produced, investigated the performance of each prototype, and the above conditions were obtained from the experimental results. is there.

FIG. 5 is a diagram showing the contents and performance outline of each prototype. The prototype is called "two-mountain type", and the distribution of the groove bottom thickness t along the circumferential direction is symmetrical between two peaks and valleys. The prototype is called an "eccentric type", and is one in which there is a distribution of the groove bottom thickness t along the circumferential direction. The prototype is called a "stepped type" and has a stepped shape at a portion having a groove bottom thickness t. In this embodiment,
It is defined as the case where there is a step of 75% or more of the difference between the maximum groove bottom thickness and the minimum groove bottom thickness. For example, the maximum-minimum groove thickness is 1
In the case of 0 μm, there are 7.5 μm steps. The prototype is
It is called "random type", and the variation of the groove bottom thickness t is randomly distributed. In FIG. 5, the average groove bottom thickness tm of the elastic body is 1.5 mm.

As shown in FIG. 6, the ultrasonic motor has a minimum driving speed NL (driving frequency fL) which avoids a frequency range where driving force and friction force are antagonized and driving becomes unstable, and a resonance point. It is driven between the maximum drive rotation speed NH (drive frequency fH) that avoids a frequency range where drive becomes unstable in the vicinity. In addition, the performance of the ultrasonic motor is from the minimum drive speed NL (drive frequency fL) to the maximum drive speed NH (drive frequency f).
It can be shown by the power consumption and the stability of drive characteristics (variation of characteristic curve) in the rotation speed band up to H). Furthermore, the maximum drive speed N that can obtain a strong drive force
H (drive frequency fH) is relatively stable, but the minimum drive speed NL (drive frequency fL) that is set before the drive becomes unstable because the drive force is weak and the frictional force is antagonistic, It was found that the thickness tends to change depending on the tendency of variation in bottom thickness. FIG. 5 shows the power consumption at the maximum drive speed NH and the drive frequency difference (fL-fH) from the minimum drive speed NL (drive frequency fL) to the maximum drive speed NH. This drive frequency difference shows the slope of the frequency-one-revolution number diagram, and in the reference characteristic shown by the solid line in FIG. 6, the drive frequency difference (fH−fL) is wide, and stable control is performed. When fL is shifted to low frequency measurement, the drive frequency difference becomes small as indicated by fH-fL ', and control becomes unstable. Further, when the speed control of the ultrasonic motor is performed by frequency, if there is an individual difference in this value, it is necessary to adjust the control parameter for each individual, which increases man-hours. That is, the larger the drive frequency difference, the better the performance of the ultrasonic motor. Therefore, an ultrasonic motor having no difference in driving frequency is desired.

As is apparent from FIG. 5, there is no significant difference in the power consumption due to the variation amount Δt of the groove bottom thickness t and the distribution shape thereof. However, with regard to the drive frequency difference, the values for the “two mountain type” and the “random type” are 15
The values tended to be smaller when the thickness was more than μm, and the values tended to be smaller when the “eccentric type” and the “stepped type” were more than 10 μm.

The average groove bottom thickness tm of this prototype is 1.5 m.
Therefore, for the “double-mountain type” and the “random type”, the driving frequency difference (fL−fH) is small when the variation width Δt varies by 1.0% or more with respect to the average groove bottom thickness tm. For the "eccentric type" and the "stepped type",
The variation width Δt is 0.7% with respect to the average groove bottom thickness tm.
The above variation results in a smaller drive frequency difference (fL-fH).

Further, the "eccentric type" and the "stepped type" have a greater effect on the performance deterioration than the "double-mount type" and the "random type". This is because the locally different thickness or the presence of discontinuities affects the waveform and phase velocity of the progressive oscillatory wave rather than the groove bottom thickness changing symmetrically or uniformly throughout. Is estimated to be given.

The progressive vibration wave generated in the elastic body 12 is obtained by synthesizing two standing waves of bending vibration generated by the excitation of the piezoelectric body 13. Therefore, when the groove bottom thickness t of the elastic body 12 varies, the amplitude distribution shapes of the two standing waves are distorted or different, and the combined progressive vibration wave may be different depending on the location. It happens that the amplitudes are different.

The progressive vibration wave is a bending wave, and the phase velocity of the wave is proportional to the thickness. Therefore, the elastic body 1
When the groove bottom thickness t of No. 2 varies, the phase velocity of the progressive vibration wave may vary depending on the place. For these reasons, it is considered that a phenomenon in which the driving frequency difference (fL-fH) becomes small is caused because the shape of the progressive vibration wave having a frequency away from resonance is disturbed and becomes smaller than a desired speed.

The cause of the variation in the groove bottom thickness t is as follows. Regarding the "double-mountain type", the shape of the elastic body before processing was a two-fold shape, and this occurred because the groove was processed in that state. The shape of the elastic body folded in two means that the drive surface of the elastic body before processing and the surface on which the piezoelectric body is attached are not flat and parallel. For the "eccentric type", cleaning after processing is insufficient,
It was caused by a foreign object being caught between the elastic body and the hire. Hire is a processing jig that fixes the elastic body. The "stepped type" occurred because the machine did not warm up sufficiently and the equipment and tools warmed up during processing. The "random type" was caused by a combination of the above three causes and the transformation of employment.

The following measures were taken based on these causes. For the double-mountain type, the elastic body before processing was double-sided lapped to improve the accuracy of parallelism between the upper and lower surfaces. For the eccentric type, the cleaning procedure after processing was specified to prevent foreign matter from remaining. For the stepped type, the procedure and time for warming up the machine were specified. For the random type, we made a hire that does not deform.

In addition to the above-mentioned measures, the variation width Δt of the groove bottom thickness t of the elastic body 12 is detected, and the distribution of the groove bottom thickness t along the circumferential direction is typified as a “two mountain type”. When the distribution of the variation width Δt is point-symmetrical and the variation width that is classified as “random” has a random distribution, Δt / tm is 0.01 with respect to the average groove bottom thickness tm.
By providing the variation within the range, an ultrasonic motor having a uniform drive frequency difference can be obtained.

When the distribution of the thickness variation width in the circumferential direction, which is categorized as the "eccentric type", is partially biased, the variation Δt / tm should be 0.007 or less. As a result, an ultrasonic motor having a uniform drive frequency difference can be obtained.

Further, in the case where the difference between the thickness of a certain groove portion which is categorized as a "stepped type" and the thickness of the groove portion adjacent thereto is defined as ts, and ts / tm is 0.005 or more, Δ By making t / tm have a variation of 0.007 or less, an ultrasonic motor having a uniform drive frequency difference can be obtained.

As a result, since the driving frequency difference of each individual becomes uniform, it is not necessary to adjust the control parameter for each individual, and the number of steps can be reduced.

The present invention is not limited to the embodiment described above, and various modifications and changes can be made, which are also within the scope of the present invention. The ultrasonic motor used in the present embodiment is an elastic body having 9 waves of progressive vibration waves and 54 grooves. However, even with progressive vibration waves of other wave numbers or other numbers of grooves, An ultrasonic motor using a progressive vibration wave can be similarly applied and the same effect can be obtained.

[0042]

As described above, according to the present invention,
The elastic body has a plurality of grooves on the drive surface side, and the distribution of the variation width with respect to each groove average thickness up to the groove bottom of the elastic body has a variation within a predetermined range, so that the driving frequency difference is uniform. Ultrasonic motors are now available.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an ultrasonic motor 10 according to an embodiment of the present invention.

FIG. 2 is an external perspective view showing a vibrator 11 and a mover 17 of the ultrasonic motor 10 of this embodiment.

FIG. 3 is a block diagram illustrating an ultrasonic motor drive controller 20 according to the present embodiment.

FIG. 4 is a diagram illustrating a groove shape of an elastic body of the ultrasonic motor according to the present embodiment.

FIG. 5 is a diagram showing the contents and performance outline of each prototype.

FIG. 6 is a graph showing the relationship between the drive frequency and the rotation speed of the ultrasonic motor.

[Explanation of symbols]

10 Ultrasonic motor 11 oscillators 12 Elastic body 12a groove 12b protrusion 12c drive surface 13 Piezoelectric body 14 Buffer member 15 Pressure plate 16 Pressure member 17 mover 18 Vibration absorbing member 19A support member 19B rotating member 20 Drive controller 21 Oscillator 22 Control unit 23 Phase shift unit 24,25 amplifier 26 Detector

Continued front page    (72) Inventor Ryoichi Suganuma             Marunouchi 3 2-3 No. 3 shares, Chiyoda-ku, Tokyo             Ceremony Company Nikon F-term (reference) 5H680 AA12 BB03 BB17 CC07 DD15                       DD23 DD35 DD39 DD53 DD74                       DD75 FF26 GG25

Claims (5)

[Claims] 1. A vibrator having a piezoelectric body excited by a drive signal and an elastic body bonded to the piezoelectric body and generating a progressive vibration wave on the drive surface by the excitation; In a vibration wave motor including a moving element that is pressure-contacted and is driven by the progressive vibration wave, the elastic body has a groove portion on a drive surface side, and a portion from a piezoelectric body joint surface to a groove bottom of the groove portion. An oscillatory wave motor characterized in that Δt / tm has a variation of 0.01 or less when the average thickness of each groove is defined as tm and the variation width of the thickness is defined as Δt. 2. The vibration wave motor according to claim 1, wherein the elastic body has a point-symmetric distribution of the variation width,
Also, the vibration wave motor is characterized in that Δt / tm has a variation of 0.01 or less. 3. The vibration wave motor according to claim 1, wherein the elastic body has a random distribution in the variation width, and Δt / tm has a variation of 0.01 or less. Characteristic vibration wave motor. 4. The vibration wave motor according to claim 1, wherein when the distribution of the variation width of the thickness in the circumferential direction is partially biased, the elastic body has Δt / tm of 0.
A vibration wave motor having a variation of 007 or less. 5. The vibration wave motor according to claim 1, wherein the elastic body defines a difference between a thickness of a groove and a thickness of a groove adjacent to the groove as ts, and ts / tm.
Δt / tm is 0.007 when is 0.005 or more.
A vibration wave motor having the following variations.