JP4182666B2 - Method for changing manufacturing process of vibration wave motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for changing a manufacturing process of a vibration wave motor having an elastic body having a plurality of grooves.
[0002]
[Prior art]
Conventionally, this kind of vibration wave motor, as known in Japanese Patent Publication No. 1-17354, etc., uses the expansion and contraction of the piezoelectric body to generate a progressive vibration wave on the driving surface of the elastic body. Elliptical motion is generated on the drive surface, and the movable element in pressure contact with the wavefront of the elliptical motion is driven. Since such a vibration wave motor has a feature of having a high torque even at a low rotation, the gear of the driving device can be omitted when mounted on the driving device, so that gear noise can be eliminated and positioning accuracy can be eliminated. There is an advantage that can be improved.
[0003]
Such a vibrator of a vibration wave motor using a traveling wave is composed of a piezoelectric body and an elastic body, and the piezoelectric body and the elastic body are firmly bonded with an adhesive or the like. The elastic body is provided with grooves of equal width at substantially equal intervals on the drive surface side opposite to the piezoelectric body bonding surface. In the elastic body, the neutral surface of the bending vibration generated inside is shifted to the piezoelectric body side by this groove, and thereby the amplitude of the progressive vibration wave on the driving surface side is expanded.
[0004]
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. The value of the resonance frequency of the standing wave of this bending vibration mainly corresponds to the value of the elastic body thickness, particularly the groove bottom thickness of the elastic body when the vibration order and outer diameter are fixed. Yes. For example, when the groove bottom thickness increases, the resonance frequency of the standing wave of bending vibration increases, and accordingly, the driving frequency band of the vibration wave motor shifts toward a higher frequency. Further, when the groove bottom thickness is reduced, the resonance frequency of the standing wave of the bending vibration is lowered, and accordingly, the driving frequency band of the vibration wave motor is shifted toward a lower frequency.
[0005]
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 check and adjust the relationship between speed and frequency, such as a zero speed frequency, a certain speed frequency, and a maximum speed frequency, for each motor. Accordingly, when the shift amount of the drive frequency band is larger than the individual difference of the vibration wave motor, man-hours are required in finding an appropriate drive frequency band.
[0006]
Further, if the shift amount of the drive frequency band is large, the oscillation unit of the drive circuit may not be able to cope with the shift amount. For this reason, it is necessary to prepare several oscillating units having different frequency bands and select them in accordance with the shift amount of the bands, resulting in a problem that the process becomes complicated.
Therefore, in order to prevent the increase in the number of processes and the process as described above and to eliminate the cost increase, it is necessary to suppress the variation in the groove bottom thickness and to reduce the shift amount of the driving frequency band.
The grooves are usually processed by a milling cutter or a grindstone, and one groove and one groove are processed.
[0007]
[Problems to be solved by the invention]
The progressive vibration wave generated in the elastic body is obtained by synthesizing two standing waves of bending vibration generated by the excitation of the piezoelectric body. In order to obtain a progressive vibration wave having a uniform amplitude at any position, the amplitude distribution shapes of the two standing waves must be uniform and substantially the same. For example, when there is variation in the thickness of the elastic body, the amplitude distribution shapes of the two standing waves are distorted or different. In this case, the synthesized progressive vibration wave has a different amplitude 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, when the thickness of the elastic body varies, the phase velocity of the progressive vibration wave may vary depending on the location.
The elastic body was expected to have stable characteristics as a vibrator if the above-described variations were eliminated at all. However, this requires ultra-high precision machining, which necessitates an increase in cost.
[0008]
On the other hand, when the elastic body has variations 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 material joining surface (hereinafter referred to as the groove bottom thickness) varies from the groove bottom of the elastic body, the amplitude of the progressive vibration wave is not uniform in the circumferential direction or the phase The speed is not uniform in the circumferential direction, and the driving performance is degraded. This has been clarified by experiments of the present inventors. In particular, according to the experiments of the present inventors, it has been found that the frequency-rotation characteristics are deteriorated and it is difficult to drive at a low speed (the slope of the frequency-rotational speed diagram changes). As described above, when the variation in the thickness of the groove bottom of the elastic body increases within the individual, there arises a problem that the performance deteriorates.
In addition, if the groove bottom thickness varies among individuals, and the slope of the frequency-rotational speed diagram changes for each individual, it is necessary to adjust the control parameters for each individual in order to perform speed control at the frequency. The problem of increased man-hours also arises.
[0009]
The subject of this invention is providing the change method of the manufacturing process of the vibration wave motor with which the drive performance improved and the man-hour of assembly adjustment was reduced.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventor has intensively studied, and as a result, found the relationship between the variation tendency of the groove bottom thickness and the characteristics of the elastic body, and it is not necessary to eliminate the variation in the groove bottom thickness at all. The inventors have invented a vibration wave motor capable of obtaining a stable vibrator while preventing an increase in cost. That is, the invention according to claim 1 is a process of forming grooves on the drive surface along the circumferential direction one by one in the annular elastic body that generates a progressive vibration wave on the drive surface by excitation of the piezoelectric body by a drive signal. a step of said driving surface vibrator by joining the piezoelectric element on the opposite side to the said elastic member, the driving surface of the elastic body, the moving element driven by the traveling vibration wave pressure A method of changing a manufacturing process of a vibration wave motor including: a step of producing at least one workpiece, and a thickness of each groove from a piezoelectric joint surface of the workpiece to a groove bottom of the groove portion t and a variation width Δt of the thickness t are detected, a distribution state along the circumferential direction of the detected variation width Δt, and a relatively large stepped portion is formed in the groove bottom thickness t. 2 points of whether or not the distribution width along the circumferential direction of the variation width Δt However, when the two peaks and valleys have a symmetrical shape, a process of applying double-sided wrapping to the elastic body before the step of forming the groove is added to the manufacturing step, and the circumference of the variation width Δt. When the distribution state along the direction exhibits a distribution shape biased to a certain part, a process for cleaning a processing jig used for fixing the elastic body in the step of forming the groove is added to the manufacturing process. In the case where a relatively large stepped portion is formed in the thickness t, the process for adjusting the warm-up operation time required for the step of forming the groove in one elastic body is performed in the manufacturing step. Rukoto addition, a method of changing the vibration wave motor manufacturing process characterized by.
According to a second aspect of the present invention, in the method for changing a manufacturing process of the vibration wave motor according to the first aspect, the case where a relatively large stepped portion is formed in the thickness t is the thickness of a certain groove portion. A method of changing a manufacturing process of a vibration wave motor, characterized in that the difference between the thickness of the adjacent groove portion is ts, the average of the thickness t is tm, and ts / tm is 0.005 or more . It is.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a vibration wave motor according to the present invention will be described below in detail with reference to the accompanying drawings. In the following embodiments, an ultrasonic motor using an ultrasonic vibration region will be described 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 the present embodiment.
[0016]
The ultrasonic motor 10 according to the present embodiment includes a vibrator 11 and a mover 17, the vibrator 11 side is fixed, and the mover (relative motion member) 17 side is rotationally driven. The buffer member 14, the pressure plate 15, the pressure member 16, and the support member 19 </ b> A are disposed below the vibrator 11, and the vibration absorbing member 18 and the rotation member 19 </ b> B are disposed above the mover 17. ing.
[0017]
The vibrator 11 is joined to an elastic body 12 and an electromechanical conversion element (hereinafter referred to as a piezoelectric body) such as a piezoelectric element or an electrostrictive element that is joined to the elastic body 12 and converts electrical energy described later into mechanical energy. 13. Although a traveling wave is generated in the vibrating body 11, in the present embodiment, as an example, a description will be given of 9 traveling waves.
[0018]
The elastic body 12 is made of a metal material having a high resonance sharpness, and has a ring shape. The elastic body 12 has a groove 12a cut on the opposite surface to which the piezoelectric body 13 is joined, and the tip surface of the protrusion (a place where the groove 12a is not provided) 12b serves as a drive surface 12c. Pressure contact.
The reason for cutting the groove 12a is to make the neutral surface of the traveling wave as close to the piezoelectric body 13 as possible, thereby amplifying the amplitude of the traveling wave on the drive surface 12c.
[0019]
The piezoelectric body 13 is divided into two phases (A phase and B phase) along the circumferential direction, and in each phase, elements with alternating polarization for each half wavelength are arranged. An interval of ¼ wavelength is provided between the A phase and the B phase.
[0020]
Under the piezoelectric body 13, a buffer member 14, a pressure plate 15, a pressure member 16, and a support member 19A are arranged. The buffer member 14 is disposed under 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 nonwoven 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 a member that is disposed under the pressure plate 15 and generates a pressurizing force. In the present embodiment, the pressure member 16 is a disc spring, but it may be a coil spring or a wave spring instead of a disc spring. The support member 19A is a member that supports the ultrasonic motor 10 on the fixed side.
[0021]
The mover 17 is made of a light metal such as aluminum, and the surface of the sliding surface 17a is subjected to surface treatment for improving wear resistance. A vibration absorbing member 18 such as rubber is disposed on the moving member 17 in order to absorb vibration in the pressurizing direction of the moving member 17, and a rotating member 19B such as a bearing is disposed thereon. Yes.
[0022]
FIG. 3 is a block diagram illustrating the ultrasonic motor drive control device 20 according to the present embodiment. First, the configuration of the ultrasonic motor drive control device 20 will be described. The drive control device 20 includes an oscillation unit 21, a control unit 22, a phase shift unit 23, amplification units 24 and 25, a detection unit 26, and the like.
[0023]
The oscillating unit 21 generates a drive signal having a desired frequency according to a command from the control unit 22. The phase shifter 23 divides the drive signal generated by the oscillator 21 into two drive signals having a 90 ° phase difference. The amplifiers 24 and 25 boost the two drive signals divided by the phase shifter 23 to desired voltages, respectively. Drive signals from the amplifying units 24 and 25 are transmitted to the ultrasonic motor 10, and a traveling wave is generated in the vibrator 11 by the application of the drive signal, and the moving element 17 is driven.
The detection unit 26 is configured by 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.
[0024]
The control unit 22 controls driving of the ultrasonic motor 10 based on a driving command from the CPU. And the control part 22 receives the detection signal from the detection part 26, acquires position information and speed information based on the value, and controls the frequency of the oscillator 21 so that it may be positioned to a target position.
[0025]
Next, the operation of the drive control apparatus 20 for the ultrasonic motor 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, and the signal is divided into two drive signals having a phase difference of 90 ° by the phase shift unit 23, and is amplified to a desired voltage by the amplification units 24 and 25. The drive signal is applied to the piezoelectric body 13 of the ultrasonic motor 10, and the piezoelectric body 13 is excited, and the excitation causes the ninth-order bending vibration to occur 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. The 9th-order bending vibration generated from the A-phase and the 9th-order bending vibration generated from the B-phase are such that the positional phase is shifted by a quarter wavelength, and the A-phase drive signal and the B-phase drive signal are Since the phase is shifted by 90 °, two bending vibrations are combined into nine traveling waves.
[0026]
The traveling wave has an elliptical motion at its wave front. Accordingly, since the movable element 17 is in pressure contact with the drive surface 12c, it is frictionally driven by this elliptical motion. The detection unit 26 is disposed on a driven body that is driven by driving the moving element 17, and an electric pulse signal generated from the detection unit 26 is transmitted to the control unit 22. Based on this signal, the control unit 22 can obtain the current position and the current speed, and controls the drive frequency of the oscillation unit 21 based on the position information, speed information, and target position information.
[0027]
FIG. 4 is a view for explaining the shape of the groove of the elastic body of the ultrasonic motor according to the present embodiment.
The elastic body 12 is provided with 54 equal-width grooves 12a at equal intervals along the circumferential direction on the drive surface 12c side. In this embodiment, b is defined as the overall height of the elastic body 12, and a 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 thickness of 54 grooves 12a is tm and the variation width of the thickness is Δt, Δt / tm has a variation of 0.01 or less. .
The inventor of the present invention intentionally created a prototype in which the variation width Δt of the groove bottom thickness t was generated, investigated the performance of each prototype, and obtained the above conditions from the experimental results. is there.
[0028]
FIG. 5 is a diagram showing the contents and performance summary of each prototype.
Prototype {circle around (1)} is called “two mountain type”, and the distribution along the circumferential direction of the groove bottom thickness t is symmetric between the two peaks and valleys.
The prototype {circle around (2)} is called “eccentric type”, and is biased to a part of the distribution along the circumferential direction of the groove bottom thickness t.
Prototype {circle around (3)} is called a “stepped type” and is stepped at a portion having a groove bottom thickness t. In the present embodiment, it is defined that 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, if the maximum-minimum groove thickness is 10 μm, there is a 7.5 μm step.
Prototype {circle around (4)} is called a “random type”, and the variation in groove bottom thickness t is randomly distributed.
In FIG. 5, the average groove bottom thickness tm of the elastic body is 1.5 mm.
[0029]
As shown in FIG. 6, the ultrasonic motor is driven in the vicinity of the resonance point with the minimum driving rotation speed NL (driving frequency fL) avoiding the frequency range where the driving force and the friction force antagonize and the driving becomes unstable. Is driven between the maximum driving speed NH (driving frequency fH) avoiding the frequency range where becomes unstable.
In addition, the performance of the ultrasonic motor is the stability of power consumption and drive characteristics (variation in characteristic curves) in the speed band from the minimum drive speed NL (drive frequency fL) to the maximum drive speed NH (drive frequency fH). Can be indicated by
Furthermore, the maximum driving speed NH (driving frequency fH) at which a strong driving force can be obtained is relatively stable, but is set before the driving force becomes weak and the frictional force antagonizes and the driving becomes unstable. It has been found that the minimum driving speed NL (driving frequency fL) is likely to change depending on the variation tendency of the groove 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 indicates the slope of the frequency per revolution diagram, and in the reference characteristics shown by the solid line in FIG. 6, the drive frequency difference (fH−fL) is wide and control is performed stably. When fL shifts to low frequency measurement, the drive frequency difference becomes small as indicated by fH−fL ′, and the control becomes unstable.
In addition, when the speed control of the ultrasonic motor is performed at a 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 in which there is no individual difference in driving frequency difference is desired.
[0030]
As is apparent from FIG. 5, there is no significant difference in power consumption due to the variation amount Δt of the groove bottom thickness t and its distribution shape.
However, with regard to the driving frequency difference, the values of “Two mountain type” and “Random type” tend to be smaller than 15 μm, and the values of “Eccentric type” and “Stepped type” are more than 10 μm. Tended to be smaller.
[0031]
Since the average groove bottom thickness tm of this prototype is 1.5 mm, the variation width Δt is 1.0 with respect to the average groove bottom thickness tm for the “double mountain type” and the “random type”. The difference in drive frequency (fL-fH) decreases when the difference is more than%, and the variation width Δt varies more than 0.7% with respect to the average groove bottom thickness tm for the “eccentric type” and “stepped type”. As a result, the drive frequency difference (fL−fH) was reduced.
[0032]
In addition, the “eccentric type” and “stepped type” had a greater effect on performance degradation than the “two mountain type” and “random type”. This is because the difference in thickness locally and the presence of discontinuities affect the waveform and phase velocity of the progressive vibration wave, rather than changing the groove bottom thickness symmetrically or uniformly. It is estimated that
[0033]
The progressive vibration wave generated in the elastic body 12 is obtained by synthesizing the standing waves of two bending vibrations 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 synthesized progressive vibration wave depends on the location. It occurs that the amplitudes are different.
[0034]
Further, the progressive vibration wave is a bending wave, and the phase velocity of the wave is proportional to the thickness. Therefore, when the groove bottom thickness t of the elastic body 12 varies, the phase velocity of the progressive vibration wave varies depending on the location. For these reasons, it is considered that a phenomenon in which the driving frequency difference (fL−fH) becomes small because the shape of the progressive vibration wave having a frequency away from the resonance is disturbed and becomes smaller than a desired speed.
[0035]
The cause of the variation in the groove bottom thickness t is as follows.
{Circle around (1)} For the “double mountain type”, the shape of the elastic body before processing is a double-folded shape, and the groove is formed in that state. The shape of the elastic body being folded in two means that the drive surface of the elastic body before processing and the surface on which the piezoelectric body is pasted are not flat and parallel.
(2) The “eccentric type” occurred because the cleaning after processing was insufficient and the chucking occurred while foreign matter was caught between the elastic body and the employer. Hiring is a processing jig that fixes an elastic body.
(3) The “stepped type” is caused by insufficient warm-up operation of the machine, and the apparatus and tools are warmed during processing.
(4) “Random type” occurred due to the combination of the above three causes and changes in employment.
[0036]
The following measures were taken based on these causes.
(1) For the double mountain shape, double-sided wrapping was applied to the elastic body before processing to improve the accuracy of the parallelism of the upper and lower surfaces.
(2) For the eccentric type, the procedure for cleaning work after processing was defined so that no foreign matter remained.
(3) For the stepped type, the procedure and time for warming up the machine were specified.
(4) For the random type, an untransformed employment was created.
[0037]
In addition to the measures described above, the variation width Δt of the groove bottom thickness t of the elastic body 12 is detected, and the distribution along the circumferential direction of the groove bottom thickness t is a variation that is categorized as a “double mountain”. For those in which the distribution of the width Δt is point-symmetric and those in which the variation width classified as “random type” has a random distribution, the variation in Δt / tm within 0.01 with respect to the average groove bottom thickness tm Thus, an ultrasonic motor with a uniform driving frequency difference can be obtained.
[0038]
Further, when the distribution of the thickness variation width in the circumferential direction, which is classified as “eccentric type”, is partially deviated, Δt / tm has a variation of 0.007 or less. An ultrasonic motor with a uniform driving frequency difference can be obtained.
[0039]
Furthermore, when the difference between the thickness of a certain groove portion categorized as a “stepped mold” and the thickness of a groove portion adjacent thereto is defined as ts, and when ts / tm is 0.005 or more, Δt / tm Has a variation of 0.007 or less, an ultrasonic motor with a uniform driving frequency difference can be obtained.
[0040]
As a result, since the difference in the driving frequency of each individual became uniform, it was not necessary to adjust the control parameter for each individual, and man-hours could be reduced.
[0041]
The present invention is not limited to the embodiment described above, and various modifications and changes are possible, and these are also within the equivalent scope of the present invention.
The ultrasonic motor used in the present embodiment is an elastic body with nine progressive vibration waves and 54 grooves. However, even with other vibration vibration waves or other numbers of grooves, An ultrasonic motor using a progressive vibration wave can be applied in the same manner, and the same effect can be obtained.
[0042]
【The invention's effect】
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 the average thickness of each groove to the groove bottom is within a predetermined range. Therefore, an ultrasonic motor with a uniform drive frequency difference can be obtained.
[Brief description of the 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 the present embodiment.
FIG. 3 is a block diagram illustrating an ultrasonic motor drive control device 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 summary of each prototype.
FIG. 6 is a graph showing the relationship between the driving frequency and the rotational speed of an ultrasonic motor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Ultrasonic motor 11 Vibrator 12 Elastic body 12a Groove 12b Protrusion part 12c Drive surface 13 Piezoelectric body 14 Buffering member 15 Pressure plate 16 Pressure member 17 Mover 18 Vibration absorption member 19A Support member 19B Rotation member 20 Drive control device 21 Oscillation Unit 22 Control unit 23 Phase shift unit 24, 25 Amplification unit 26 Detection unit

Claims (2)

Forming a groove portion in the drive surface along the circumferential direction in an annular elastic body that generates a progressive vibration wave on the drive surface by excitation of the piezoelectric body by a drive signal;
Bonding the piezoelectric body to a surface opposite to the drive surface of the elastic body to form a vibrator;
Wherein the drive surface of the elastic member, a moving member driven by the traveling vibration wave process and to pressure contact; a modified method of the vibration wave motor of the manufacturing process including,
Make at least one workpiece,
Detecting the thickness t of each groove from the piezoelectric joint surface of the workpiece to the groove bottom of the groove and the variation width Δt of the thickness t ;
Investigating two points of the distribution state along the circumferential direction of the detected variation width Δt and whether or not a relatively large stepped portion is formed in the groove bottom thickness t ,
When the distribution state along the circumferential direction of the variation width Δt exhibits a symmetric shape between two peaks and valleys, a process of performing double-sided wrapping on the elastic body before the step of forming the groove portion, In addition to the manufacturing process,
When the distribution state along the circumferential direction of the variation width Δt exhibits a distribution shape biased to a certain part, a process of cleaning a processing jig used for fixing the elastic body in the step of forming the groove portion is performed. In addition to the manufacturing process,
When a relatively large stepped portion is formed in the thickness t, a process for adjusting the warm-up operation time required for the step of forming the groove in one elastic body is added to the manufacturing process. how to change the manufacturing process of the vibration wave motor which is characterized Rukoto, it was added. In the change method of the manufacturing process of the vibration wave motor according to claim 1,
In the case where a relatively large stepped portion is formed in the thickness t, the difference between the thickness of a certain groove and the thickness of the adjacent groove is ts, the average of the thickness t is tm, and ts / tm is 0. changing the manufacturing process of the vibration wave motor, characterized in that 005 is time exhibiting more.

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