JPS63114576A - Opposed driving type ultrasonic motor - Google Patents

Abstract

PURPOSE:To improve driving output and driving efficiency, by providing a pair of ultrasonic piezoelectric transducers equipped with output end faces elliptically vibrating in synchronization with both faces of a moving substance. CONSTITUTION:Electrode plates 11 and 13 of ultrasonic piezoelectric transducers 4 and 4' are connected together to form a common terminal. When alternating voltage is applied to an electrode plate 10 for axial driving to match the axial resonance frequency, output end faces 21 and 21' resonantly vibrate in an axial direction. On the other hand, if the alternating voltage applied to a torsional driving electrode plate 12 is matched with the torsional resonance frequency, then the output end faces 21 and 21' will perform torsional resonance vibration. The output end faces 21 and 21' driven in such vibrating pose are provided on both sides of a rotor disk 23 and are pressed so tightly that the rotor disk 23 is driven when the motor is synchronously driven with the respective ultrasonic piezoelectric transducers 4 and 4' axially in the same phase and torsionally in the counter phase.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an ultrasonic motor using an ultrasonic vibrator that generates complex vibrations and whose output end face vibrates elliptically.

Conventional technology Generally speaking, ultrasonic transducers for driving ultrasonic motors include:
There are traveling waveforms and standing waveforms, and both generate complex vibrations such as an ellipse on the output end face to drive a movable body such as a rotor that is crimped to the output end face.

Among these, those with standing waveforms include, for example,
Vibration piece type as seen in Publication No. 37672 and Japanese Patent Application Laid-open No. 6
There is one equipped with a cantilever-like torsion transducer as seen in Japanese Patent No. 1-52166.

The former has the disadvantage of significant wear between the vibrating piece and the contact part of the rotor, and the generation of a large amount of noise, but the latter has a larger joint area than the vibrating piece type, and is attracting attention as a solution to the drawbacks of the vibrating piece type. has been done.

However, in the case of a type that uses a cantilever-shaped torsion transducer, the vibration mode at the output end is uniformly determined by the shape of the torsion transducer, and it is difficult to control the optimum mode for frictional drive and to determine the direction of rotation. It is impossible to control.

For this reason, it is conceivable to generate compound vibrations by driving axial vibrations and torsional vibrations, or axial vibrations and vibrations perpendicular to the axis individually, and the applicant has already patented this idea. An application has been filed. For example, Japanese Patent Application No. 60-252526, which can also be driven linearly, and Japanese Patent Application No. 60-266617, which has a combination of flexural vibration and shaft vibration.
No. 61-819 consisting of torsional vibration and shaft vibration
Some examples include those described in Publication No. 22. According to these, it has become possible to electrically control and drive a vibration state such as an optimal elliptical shape depending on the rotation speed, load torque, rotation direction, etc.

Problems to be Solved by the Invention As mentioned above, by individually driving vibrations in the axial direction and torsional direction, or in the axial direction and in the perpendicular direction to the axis, the amplitude and relative phase of each can be controlled to generate various complex vibrations. However, when constructing an ultrasonic motor using such an ultrasonic vibrator, if you try to increase the output torque, you will inevitably have to apply a large amount of stress to the output end face of the vibrator and the movable body. It must be welded with pressure. In other words, the output torque of the motor depends on the frictional force based on the friction coefficient of the bonding surfaces that corresponds to the axial pressing force between the output end face of the vibrator and the movable body, and cannot exceed this value. . Therefore, when a large output torque is required, the axial pressing force is increased.

Ultrasonic motors are characterized by the ability to achieve low speed and large torque effects, but when the pressurizing force is increased to increase the output torque, elastic deformation of movable bodies such as the rotor causes Eventually, the joint surfaces become unable to separate from each other over the entire period of vibration, causing a problem in that the moving speed of the movable body is extremely reduced, drive loss in the feeding direction increases, and drive efficiency is significantly reduced.

Such a phenomenon will be explained based on FIGS. 9 and 10. First, in FIG. 9, 1 is a movable body in a stationary state, and 2 is an output end face of an ultrasonic transducer in a stationary state. Curve A represents the temporal displacement of the output end surface 2 in the axial direction, and curve B represents the temporal displacement of the axial pressing force P between the movable body 1 and the output end surface 2. Further, a dashed line continuous with the curve A indicates the displacement of the output end surface 2 of the ultrasonic transducer in a state where the movable body 1 is not present. FIG. 10 shows the elliptical vibration state of the vibrator output end face 2 and the joined state with the movable body 1. Further, an arrow 3 indicates the feeding direction when the elliptical vibration of the output end face 2 rotates in the direction of the arrow.

However, in the state shown in FIGS. 9(a) and 10(a), the joint surface between the movable body 1 and the output end surface 2 is separated in a stationary state, and the output end surface 2 is separated by ultrasonic vibration. is displaced like curve A. As a result, during the period C between E and F, the joint surface between the movable body 1 and the output end surface 2 is pressed, and the pressing force P is generated as shown by curve B. Then, at point F, the two separate. Since there is little change in the speed of the movable body 1 in the feeding direction during the period C when both are in contact, the movable body 1 is driven at approximately the maximum speed, but since the pressing force P is small, the frictional force is small.
Output torque is small.

The state shown in FIG. 9(b) and FIG. 10(b) is a state in which the joint surface of the movable body 1 and the output end surface 2 is in contact with each other in a stationary state, and the half period of ultrasonic vibration is a state in which the joint surface of the movable body 1 and the output end surface 2 is in contact with each other. The joint surface between the body 1 and the output end surface 2 is under pressure. Therefore, since the crimp force P during welding increases, the output torque increases, but
Since the instantaneous speed in the driving direction changes within the joining period C, slipping of the joining surface begins to occur and the driving speed decreases slightly.

In the states shown in FIGS. 9(C) and 10(C), the movable body 1 and the output end surface 2 are pressurized with a preload force P' in a stationary state. In case 2, the two are separated for a short period of time and are joined for most of the period C, and therefore the pressing force P is also large, so the output torque also increases rapidly. However, since the vibration speed in the driving direction changes greatly within the contact period C, and the instantaneous speed can be zero or negative, loss due to slip increases and the rotational speed further decreases.

In the states shown in FIGS. 9(d) and 10(d), the preload force P° is set so that the movable body 1 and the output end face 2 are in contact during all cycles in the vibration state. It is. In this case, the loss due to slip increases rapidly and the number of revolutions decreases sharply. When the axial amplitude is increased in this state, a moment occurs when the two are separated, the driving speed increases, and the loss due to slip decreases. However, as the axial amplitude increases, chatter phenomenon due to abnormal resonance of the movable body l becomes more likely to occur.
This results in an unstable joint state, and the output J torque decreases. In this way, the movable body 1 escapes due to the pressure force generated by the vibration, and a sufficient pressure force cannot be obtained between the joint surfaces.

The problems based on the above phenomena can be summarized as follows.

1. Unless the pressurizing force is increased, the output torque related to the friction coefficient of the joint surface cannot be increased.

2. If the pressurizing force is large, the driving loss will increase due to the speed difference during joining and slip due to reverse driving, and the driving speed will decrease, so the axial amplitude needs to be increased by a considerable amount to create a separation period. .

3. The larger the axial amplitude is, the more the axial drive loss, which is ineffective against the output torque, increases, reducing the overall efficiency. Moreover, abnormal resonance vibration is generated and the output torque is reduced.

In this way, mutually contradictory conditions exist, making it impossible to perform optimal driving.

Means for Solving the Problems A pair of ultrasonic transducers each having an output end face that vibrates elliptically in synchronization is provided, and the output end faces of the ultrasonic transducer are arranged opposite to each other on both sides of a movable body.

Because the working movable body receives synchronized ultrasonic vibrations from both sides, it becomes hard against ultrasonic vibrations in the axial direction, and strong crimp force can be obtained during welding, and even if a large pressure force is applied, it will not last more than half a cycle. It is possible to reliably obtain a separation period and drive with high drive efficiency.

Embodiment A first embodiment of the present invention will be explained based on FIGS. 1 to 4. This embodiment is a rotary type ultrasonic motor, and includes two ultrasonic vibrators 4, which have the same shape and the same vibration characteristics.
4'.

First, the ultrasonic vibrator 4 includes an annularly formed electrostrictive element 6.7 for longitudinal vibration and an electrostrictive element 8.9 for torsional vibration,
The electrostrictive elements 6, 7 for longitudinal vibration are polarized in the thickness direction and provided with electrodes on both sides, and the electrostrictive elements 8, 9 for torsional vibration are polarized in the circumferential direction and provided with electrodes on both sides. , respectively, generate longitudinal vibration and circumferential direction vibration, that is, torsional vibration, by applying an alternating electric field in the thickness direction.

The longitudinal vibration electrostrictive elements 6, 7 and the torsional vibration electrostrictive elements 8.9 are arranged with electrode plates 10, 11, 12° 13 in between, and a center hole 14 is formed on both sides of the electrostrictive elements 6, 7 and torsional vibration electrostrictive elements 8.9. and a metal member 16 provided with an acid screw 15 and an annular metal member 17
are arranged and fastened together with a hollow bolt 18 and a nut 19. Note that the electrostrictive elements 6, 7, 8.9
An insulating pipe 20 is inserted between the inner periphery of the electrode plates 10, 11, 12, 13 and the hollow bolt 18 to maintain electrical insulation. Each of the sonic wave transducers 4, 4' has an output end face 21, 21' at one end thereof.

Next, a disk-shaped rotor disk 23 is provided as a movable body, and flanges 22, 22° fixed to the rotor shafts 5, 5' are joined to both sides of the center of the rotor disk 23, and fixed thereto. There is. The rotor shafts 5, 5' are connected to the hollow bolt 18 and the center hole 14.
The ultrasonic transducers 4 and 4' are inserted into the frame X and held by bearings 24 and 24' provided on the frame
It is maintained by 5.

The output end faces 21, 21' are arranged opposite to each other on both sides of the rotor disk 23 and are crimped.

In such a configuration, if the electrode plates 11 and 13 of the ultrasonic transducers 4 and 4' are connected as a common terminal and an alternating voltage is applied to the axial drive electrode plate 10 to match its axial resonance frequency, The output end faces 21, 21' vibrate resonantly in the axial direction,
Furthermore, if the alternating voltage applied to the torsional driving electrode plate 12 is matched to the torsional direction resonance frequency, the output end faces 21, 21'
performs torsional resonance vibration. At that time, the distribution state of each vibration amplitude in the torsional direction and axial direction is shown in Fig. 1 (b).
As shown in Figure 1(c), the torsional vibration has one wavelength,
The shaft vibration resonates at 1/2 wavelength.

Here, the small diameter portion 2G formed from the torsional vibration node of the metal member 16 to the output end face 21 is provided to match the torsional vibration frequency and the shaft vibration frequency, and the difference in frequency is minimized. It is preferable.

Therefore, when an alternating voltage at the resonance frequency is applied with the relative phase of the axial and torsional drive voltages at 90 degrees, the output end face 21
, 21' perform elliptic vibration, which is a composite vibration mode of axial vibration and torsional vibration, as shown in FIG.

Therefore, the output end face 21 driven in such a vibration state
, 21'' are arranged and crimped on both sides of the rotor disk 23 as shown in FIG. When driven synchronously with opposite phases, the rotor disk 23 repeats the cycle of simultaneously joining and crimping the rotor disk 23 near the apex of each elliptical vibration and then separating, as shown in FIG. It is driven in the direction of the bold arrow.

Here, FIG. 4 shows the operating state of the connection between the rotor disk 23 and the output end face 21.degree. 21'. Vibration displacement A, A'
is exaggerated to represent its amplitude greatly for explanation.

Therefore, the position of the output end face 21.21'' when it is at rest is indicated by ' on the reference line, but when it is free, it vibrates in a sinusoidal wave as shown by the dashed line.However, since the rotor disk 23 exists, Period C is rotor disk 2
3, both output end faces 21, 21' are joined at the same time and are strongly pressed, resulting in a state in which the apex is missing as shown by solid lines A and A''.

Since this point is the most important point of the present invention, it will be explained in detail below.

First, if we compare it with Fig. 9(a), Fig. 9(a)
In , the vibration displacement during the period C in which the movable body 1 is in contact with the movable body 1 is distorted from the vibration waveform when the movable body 1 is not joined, but is displaced toward the movable body 1 side. This is because the movable body 1 is pushed by the vibration pressure and escapes, and the displacement is in balance with the repulsive force. Therefore, since a sufficient pressing force P cannot be obtained, the frictional force is small and only a small amount of rotational torque can be obtained.

On the other hand, in the state shown in FIG.
3 is pressed simultaneously from both sides during the bonding period C, so
There is no place for the rotor disk 23 to escape, and the strong pressing force P
is obtained. Since the instantaneous pressing force P is strong as shown by curve B in FIG. 4, the resulting frictional force is also large, and therefore a strong driving force in the rotational direction is obtained. Moreover, in addition to the strong pressure applied during joining, the rotor disk 23 is completely free during the rest of the time, so no force that impedes rotational drive is applied to the joining surfaces, leading to a decrease in rotational speed due to slipping and wear. This eliminates this problem, resulting in longer life of the joint surface and higher drive efficiency. □Also, even though the crimp force is large during welding, the static prestress requires only the value P', which is the integral of the crimp force P over time, so the static prestress for the rotational torque obtained is It is good that it is quite small.

For this reason, it is desirable that the rotor disk 23 be thinner. This is because when crimped from both sides,
This is because if the thickness is large, elastic deformation occurs in the thickness direction, causing a slight relief toward the center, and the instantaneous pressing force decreases for the same vibration displacement. In addition, the rotor disk 23
The less the material is elastically deformed, the better.

Note that the maximum output torque of the ultrasonic motor using two ultrasonic vibrators 4, 4' having the same characteristics can be obtained to be more than twice the maximum output in the torsional direction allowed by each vibrator. Further, the number of torsional drive electrostrictive elements 8.9 may be determined depending on the required rotational output of each vibrator.

Next, a second embodiment of the present invention will be described based on FIGS. 5 to 8. Vibrator 30.30' in this example
is a patent application filed in 1986-252 by the present applicant.
No. 526. That is, the annular electrostrictive element 31 polarized in the thickness direction is formed with an electrode 33 provided on one surface leaving an insulating portion 32, and an entire surface electrode 34 provided on the other surface. Two electrostrictive elements 31 are stacked with electrode plates 35 and 36 having the same shape as the electrode 33 and having terminal portions 37 and 38 in between so as to face their divided electrode surfaces. A metal member 3 has an exponential step on both sides and a bolt threading hole in the center of the large diameter side.
9 and a ring-shaped metal member 40 are laminated and integrally fastened with bolts 42.

Therefore, by connecting terminals 37 and 38 in parallel, common terminal 4
When an alternating voltage is applied to the vibrator 1 and its frequency is matched to the axial resonant frequency, resonant vibration occurs in the axial direction like a commonly known vertical vibrator. Furthermore, when alternating voltages with opposite phases are applied to the terminals 37 and 38 to match the frequency to the flexural resonance frequency, the output end 43 causes flexural resonance vibration in a direction perpendicular to the axis.

Here, the axial and flexural resonance frequencies are matched by the exponential step of the metal member 39 and the shape of the notch 44, and the relative phases and amplitudes of the alternating voltages applied to the terminals 37 and 38 are controlled. As a result, the vibration state of the output end face 43 can be freely controlled in terms of linear vibration and its vibration direction, and elliptical vibration and its ellipticity and rotation direction.

Further, the rotor disk 45 as a movable body is connected to the shaft 4.
The output end surfaces 43 of the two vibrators 30 and 30' are pressed against each other from both surfaces near the outer periphery of the rotor disk 45 so as to face each other.

When such vibrators 30, 30'' are synchronized and vibrated elliptically in the direction shown in FIG. 8, the rotor disk 4
5 is rotationally driven in the direction of the white arrow.

Furthermore, in practice, if a long linear strip is used in place of the rotor disk 45, the rotor disk 45 can be effectively driven as a linear drive that moves in a straight direction. Furthermore, the band plate may be fixed and the paired vibrator may be moved.

Note that as long as the vibrator has controllable elliptical vibration, vibrators based on various operating principles can be usefully used.

Effects of the Invention As described above, the present invention provides synchronized axial vibration on both sides of the movable body by disposing a pair of slow-sonic vibrators each having an output end surface that vibrates elliptically in synchronization with both sides of the movable body. By applying ultrasonic vibration pressure, a strong frictional force in the driving direction can be obtained, and a reliable separation period of more than half a cycle can be obtained, increasing the driving output and reducing the rotational speed due to slipping of the joint surface. There is no drop or loss in the torsional direction, increasing driving efficiency, and since there is no slipping, wear on the joint surfaces can be significantly reduced, resulting in a long life.

[Brief explanation of the drawing]

Fig. 1(a) is a partially cutaway front view showing the first embodiment of the present invention, Fig. 1(b) and (C) are characteristic diagrams showing the vibration amplitude distribution, and Fig. 2 shows a pair of FIG. 3 is a partial cross-sectional view showing the state of elliptical vibration of the output end surface of the rotor disk portion, and FIG. 4 is a partial perspective view showing the output end face of the ultrasonic vibrator. Characteristic diagram showing the relationship between
The figure is a perspective view showing a second embodiment of the present invention, FIG. 6 is a perspective view of an electrostrictive element, FIG. 7 is a perspective view of an electrode plate, and FIG. 8 is a relationship between a rotor disk and an output end surface. Partial front view, Figures 9(a), (b), (c), and (d) are characteristic diagrams showing the relationship between axial vibration and axial pressing force in a conventional ultrasonic motor, and Figure 10(a) (b), (c), and (d) are characteristic diagrams showing the relationship between the movable body and the output end face that vibrates elliptically. 4.4゛... Ultrasonic transducer, 21.21'... Output end face, 23... Rotor disk (movable body), 30° 30''... Vibrator (ultrasonic transducer), 43 ...Output end face, 45...Rotor disk (movable body) Applicant: Taga Electric Co., Ltd., %Z a) (b) (c)
(cl) (C)
(d) Procedural amendment (Private JRI 1, Indication of the case, Japanese Patent Application No. 61-260396 2, Title of the invention: Opposed drive type ultrasonic motor 3, Person making the amendment. Relationship with the case: Patent applicant 4, Attorney. Person〒107 Corrected to "inserted with loose fit."

Claims (1)

[Claims] 1. A pair of ultrasonic transducers each having an output end surface that synchronously vibrates in an elliptical manner is provided, and the output end surfaces of the ultrasonic transducer are arranged opposite to each other on both surfaces of a movable body. Opposing drive type ultrasonic motor. 2. The opposed drive type ultrasonic motor according to claim 1, wherein the movable body is a disc-shaped rotor. 3. A patent characterized in that the ultrasonic vibrator is equipped with an electrostrictive element for driving in a torsional direction and an electrostrictive element for driving in an axial direction, and has a through hole in the center of the axis through which a rotor shaft integrated with a movable body passes. A counter-drive type ultrasonic motor according to claim 1. 4. A counter-drive type ultrasonic motor according to claim 1, wherein the movable body is a strip-shaped elongated plate. 5. The opposed drive type ultrasonic motor according to claim 4, characterized in that the elongated plate is fixed and the ultrasonic vibrator is moved.