JPH0667230B2 - Forward / reverse rotation drive - Google Patents

Description

TECHNICAL FIELD The present invention relates to a forward / reverse rotation drive device driven by a standing wave, which is applicable to a rotary ultrasonic motor (vibration wave motor) or the like.

[Conventional technology]

It is known that ultrasonic vibration generated by applying an alternating voltage to an electrostrictive element or a piezoelectric element can be converted into rotational movement or linear movement, and ultrasonic waves that use the movement thus obtained as a driving force. Various motors have been proposed.

Since this ultrasonic motor does not require a winding coil, it has the advantages that it has a simple structure and can be downsized as compared with conventional electromagnetic motors, and it can obtain high torque even at low speed rotation. ing.

The representatives of this type of ultrasonic motor are as follows.

(1) A motor using a traveling wave that vibrates a rod-shaped vibrating body and moves in the length direction.

(2) A motor in which two types of standing waves having different phases in time and space are generated in a ring-shaped vibrating body, and these standing waves are combined into a traveling wave.

(3) A motor that combines vertical vibration and torsional vibration, or vertical vibration and lateral vibration of a vibrating element.

[Problems to be solved by the invention]

In the motor of (1), it is necessary to provide an absorber at the end of the rod-shaped vibrating body and cancel the reflection of the traveling wave at the end or provide an energy feedback system. However, even if an absorber is provided at the end of the vibrating body, the vibration absorbed by the absorber changes to heat, and the efficiency cannot be improved. Further, the structure becomes complicated when the energy feedback system is provided.

The motor of (2) requires special consideration, such as superimposing two types of standing waves, and has a complicated structure and is difficult to control efficiently.

The motor of (3) also had to synthesize two types of vibrations, and had a complicated structure and poor efficiency.

[Object of the Invention]

The present invention is based on a principle different from a method using a traveling wave and a vibration synthesis method which have been conventionally performed, and a standing wave applied to a vibrating body can be efficiently converted into a positive rotation motion and a reverse rotation motion. An object is to obtain a reverse rotation drive device.

[Means for solving problems]

According to the conventional idea of traveling wave motors, a standing wave is a superposition of waves traveling in opposite directions, so if the strength of both waves is equal, move the object in a specific direction. I can't.

However, as a result of experiments, the standing waves have the ability to move partially in different directions, and it is possible to move an object in a certain direction by selecting only the ability to move in that particular direction. I understood.

That is, when a bending standing wave is excited in a vibrating body such as an elastic body, its abdomen vibrates in a direction perpendicular to the vibrating body,
The node vibrates in a direction parallel to the vibrating body, but the abdomen,
It is empirically derived that there are kinetic forces opposite to each other with the node as a boundary, and kinematic abilities in the same direction exist at an arbitrary point on one surface of the vibrating body and a point on the back side thereof.

Therefore, the present invention provides a position between a node and an antinode of a standing wave generated in an annular vibrating body having a length that is an integral multiple of the wavelength of the vibration generated by the vibration source, from the antinode of the standing wave to the node direction. The extractor such as a convex portion for selecting the motion component of is extracted, and the direction of the motion component selected by this extractor is selectively switched by the selecting means, so that the contact body such as a rotor and the vibrating body that come into contact with the extractor are relatively moved. It is designed to rotate forward and backward.

[Principle of the Invention] As described above, the standing wave has motion abilities that partially differ in direction, and the inventor has learned that an object can be rotated or moved by selecting only the motion abilities in that specific direction. But I will explain the experiment that supports it.

As shown in Fig. 1, a plate-shaped elastic body (thickness 15 mm, width 10 mm, length
250mm brass rod) 1 is vibrated by a vibration source 2 such as a Langevin oscillator (excitation frequency 43.2KHz),
A bending standing wave was generated in the elastic body 1, the roller 3 was pressed against the elastic body 1, and the relationship between the rotation direction and the position was examined.

As a result, as shown in FIGS. 2A and 2B, A to H and A'to
It was found that the rotation direction changes alternately at the position H '.

On the other hand, the wavelength λ of the bending wave will be calculated from the equation λ ² = 4π ² (E / 12ρ) ^1/2 · b / ω. Here, E is Young's modulus, ρ is the density of the rod, b is the thickness of the rod, and ω is the angular frequency. Therefore, (E / ρ) ^1/2 = 3480 × 10 ³ (vertical vibration speed of the bar) b = 5 ω = 2π × 4.32 × 10 ⁴ , and thus λ = 26.9 [mm].

Comparing this ground with FIG. 1, it can be seen that the central portion of the elastic body 1 has a pitch of approximately 13 mm, which is close to λ / 2.

From this, the position where the rotation direction of the roller 3 changes is considered to be the node or antinode of the standing wave, and can be described as follows.

The rotation direction of the roller 3 is opposite between the front and back of the elastic body 1, and the rotation is the same in the region of λ / 4 from the node to the antinode,
The rotation directions are opposite to each other in the adjacent areas.

Here, a qualitative consideration is given to the above.

If vibration is present as a traveling wave Uy = A · sin (ωt−kx) (k = 2π / λ) in the thickness direction in a plate with a thickness of 2e (e is 1/2 of the plate thickness), the wave is in the traveling direction. With the component Ux = −e · Uy ′ = e · A · K · cos (ωt−kx), each part of the traveling wave makes an elliptic motion.

Now, assuming that a standing wave is excited in the plate, and the vibration in the thickness direction is Uy = Asinωt · sinkx…, the equation is accompanied by the vibration in the X direction as in the case of the traveling wave, and Ux = −e ・Uy ′ = − e · A · K · sinωt · coskx ...

According to the equation, the standing wave of the plate is different from the standing wave of the string (e = 0), and it can be seen that the node of Uy = 0 vibrates in the X direction at −e · A · k · sinωt. Also, from Uy / Ux =-(1 / ek) tankx, it follows that each part of the plate is performing linear vibration with an inclination of (-tankx) / (ek). (Fig. 3) Considering the vibration pattern of the standing wave of the plate based on the above consideration, it becomes as shown in Fig. 4.

Comparing FIG. 4 with the above experiment, it can be seen that the rotation direction and the vibration direction of the roller 3 correspond to each other.

Considering the case where a traveling wave is excited in an annular elastic body assuming the above results, the above results will be examined. When exciting a traveling wave in an annular elastic body, a sine wave standing wave with a phase shift of π / 2 is synthesized from a spatial position shift of λ / 4.

sin (ωt-θ) = sinωt · cosθ-cosωt · sinθ = sinωt · cosθ + sin (ωt + π / 2) · cos (θ + π / 2) Overlapping standing waves with wavelengths λ / 4 shifted means the third In the figure, the right half is overlapped with the left half, and the same kind of longitudinal vibration and transverse vibration are superposed on the node N and the antinode L. However, at that point, two vibrations that are not necessarily orthogonal are superimposed.

Since the two vibrations are out of phase with each other by π / 2 in time, it can be seen that the node N and the antinode L have the same elliptical motion with a phase difference of π, but other points also have the same elliptic motion as shown below. You can see that

X component at any point; -e-A-k-sin ωt-coskx-e-A-k-sin (ω
t + π / 2) · cos (kx + π / 2) = − e · A · k · sin (ωt−kx) Y component at any point; Asinωt · sinkx + Asin (ωt + π / 2) · sin (kx + π / 2) = Acos ( ωt−kx) That is, even if an equation is assumed as a bending standing wave, the synthesis of traveling waves by two types of standing waves is explained, and the equation is considered to be close to the actual vibration.

Conventional ultrasonic motors, whether of the traveling wave type or the vibration synthesis type, have been devised so that the contact point with the movable body makes an elliptical motion.However, in the standing wave type motor described here, Is considered to drive the movable body by linear vibration as shown in FIG.

The reason why the movable body can be driven even by the linear vibration as shown in FIG. 3 is that the movable body cannot completely follow the vibration because the acceleration of the ultrasonic vibration is extremely large. It appears in the phenomenon of friction reduction due to.

From the above, the standing wave has movement capabilities partially different in rotation direction, and it is possible to move the object in a specific direction by selecting only the specific direction.

[First Embodiment] A first embodiment of the present invention (an ultrasonic motor for rotating one rotor forward and backward) will be described below with reference to FIGS. 5 to 8.

As shown in FIG. 5, the ultrasonic motor in this embodiment has a vibrating body (for example, an elastic ring) 80, a vibration source (for example, a piezoelectric ring) 81, a contact body (for example, a rotor) 84, a high frequency power supply 86. , And a selection switch 87, for example.

The contact body 84 is a disc or ring formed of a synthetic resin such as acrylic or a metal plate, and is in pressure contact with the vibrating body 80.

The vibrating body 80 is made of metal such as brass or aluminum,
An extractor (for example, a convex portion such as a protrusion) 83 (a width is an angle α) for selecting a specific moving direction of the bending standing wave,
At a position between the node of the bending standing wave S and the antinode (between quarter wavelengths), a region of an odd multiple or even multiple of a quarter wavelength (λ / 4),
For example, a plurality of the standing waves to be excited are provided at equal intervals at an interval of ½ wavelength (λ / 2) (β in angle).

The vibrating body 80 has a ring length that is an integral multiple of the wavelength λ of the standing waves Sa and Sb. The width of the extractor 83 is set to be equal to or less than a quarter wavelength of the standing wave.

The vibration source 81 is a ring-shaped piezoelectric ceramic having the first piezoelectric element array A and the second piezoelectric element array B polarized in opposite directions for each half wavelength, and has a standing wave near the extractor 83. The knots are attached to the vibrating body 80.

This vibration source 81 is, as shown in FIG.
On the other hand, the second piezoelectric element array B is displaced by λ / 4. That is, a part of the vibrating body 80 has no polarity λ /
Λ / 2 each with an unpolarized region 85 of 4 lengths interposed.
Piezoelectric element rows A and B are arranged at intervals.

Therefore, as shown in FIG. 8, the first standing wave Sa generated by the piezoelectric element array A is divided into λ / 4 lengths at the antinode and the node per wavelength λ, and the first to fourth sections a1 ~ A4, the extraction body 83 of the vibrating body 80 located on the first piezoelectric element array A is the first
Are located in the odd-numbered λ / 4 sections a1 and a3 of the standing wave Sa. Further, since the extraction bodies 83 on the second piezoelectric element array B side are also arranged in the same λ / 2 phase relationship as those on the first piezoelectric element array A side, the odd-numbered ones of the first standing wave Sa are arranged. λ / 4 section a1, a3
Is located. As a result, when the first piezoelectric element array A is excited, the contactor 84, which is the rotor, rotates clockwise.

On the other hand, all the extraction bodies 83 of the vibrating body 80 are even-numbered λ / 4 sections a2, a4 of the second standing wave Sa generated by the second piezoelectric element array B.
Since the second piezoelectric element array B is excited, the contact body 84 rotates counterclockwise.

In addition, as shown in FIG. 5, each piezoelectric element array A, B has a high frequency power source 8
6 is connected via a changeover switch 87, and either of the piezoelectric element rows A and B can be excited by switching and selecting the switch 87, whereby the contact body 8
4 can be rotated in any direction.

In this embodiment, the non-polarized region 85 for shifting the arrangement of the second piezoelectric element array B with respect to the first piezoelectric element array A by λ / 4 may be arranged in line symmetry or may be asymmetrical. . That is, the number of piezoelectric elements in the row A and the number of piezoelectric elements in the row B may be different.

According to the embodiment described above, the standing wave generated in the vibrating body 80 vibrates in the direction perpendicular to the vibrating body 80 at the antinode thereof, and vibrates in the direction parallel to the vibrating body 80 at the node. But
The abdomen and the knuckle are used as boundaries to have mutually opposite motor forces.

Therefore, the vibration source 81 is divided into the first piezoelectric element array As and the second piezoelectric element array B, and one type of high-frequency power source 86 and piezoelectric element array As.
By selectively switching A and B with the switch 87,
It is possible to obtain a simple vibration wave motor having a structure capable of forward and reverse rotation without changing the position of the extractor 83.

When a bending traveling wave is excited in a ring-shaped elastic body,
In order to make the standing wave as small as possible, special consideration is required, such as superimposing two types of standing waves. However, this is not necessary in this vibration wave motor that positively uses the standing wave.

[Second Embodiment] Next, a second embodiment of the present invention (an ultrasonic motor in which two rotors rotate in mutually opposite directions and their rotation speeds are different from each other) will be described with reference to FIGS. 8 and 9. Will be described with reference to.

In the vibrating body (for example, elastic body ring) 243 of this embodiment, the extraction bodies (for example, protrusions such as protrusions) 249 and 250 for selecting a specific motion direction of the bending standing wave are the nodes and antinodes of the bending standing wave. At a position (between 1/4 wavelengths), areas a1 and a3 at odd multiples of 1/4 or areas a2 and a4 at even multiples, for example, at intervals of 1/2 wavelength of the standing wave excited. A plurality are provided at intervals.

The vibrating body 243 has a ring length that is an integral multiple of the wavelength of the standing wave. The widths of the extractors 249 and 250 are not more than a quarter wavelength of the standing wave, and the widths of the extractors 249 and 250 are made different.

Further, contact bodies (for example, rotors) 241 and 242 that come into contact with the extraction bodies 249 and 250, respectively, are provided on the concentric circles.

The vibration source and the selection means are the same as those in the first embodiment.

Therefore, when bending vibration is generated in the vibrating body 243 and, for example, excitation is performed so that the ring length becomes a standing wave of 9 wavelengths, the extraction bodies 249 and 250 arranged at equal intervals for every 1/2 wavelength of the standing wave.
A node of a standing wave occurs near. At that time, extract 249,25
Since the width of 0 is different, the extraction amount of the unidirectional motion component is different between the extraction body 249 and the extraction body 250. Therefore, the contact body 241
The rotation speed can be different while rotating the contact body 242 and the contact body 242 in the same direction.

Further, by switching the selection means, both contact bodies 241 and 242 can be reversed.

[Third Embodiment] FIGS. 10 and 11 of a third embodiment of the present invention (an ultrasonic motor capable of rotating two rotors in opposite directions and reversing them). Will be described with reference to.

This embodiment is a rotary motor that simultaneously rotates the contact bodies 114a and 114b, which are rotors, in opposite directions. The vibration source and selecting means in this embodiment are also the same as those in the first embodiment.

The vibrating body 110 of this motor includes the first extractor 113a in the inner row.
And the second extractors 113b in the outer row are provided coaxially. The extractor 113a in the inner row is positioned at the odd-numbered a1, a3 of the λ / 4 section of the standing wave caused by the vibration source, and the extractor 113b in the outer row is the even-numbered a2, a4 in the same λ / 4 section.
Position. By this, 1 attached to the vibrating body 110
By driving the two vibration sources to excite, it is possible to cause the two contact bodies 114a and 114b to simultaneously perform rotational movements in mutually opposite directions.

Further, by switching the selection means, the contact bodies 114a and 114b can be reversed in different directions.

[Modification]

Although the three embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and the following modifications are possible, for example.

(1) In each of the above-described embodiments, the example in which the contact body rotates has been described, but the contact body may be fixed and the vibrating body may rotate. That is, it is sufficient that the vibrating body and the contact body rotate relative to each other.

(2) Although the convex portion is shown as the extractor, it may be a roller or a wave-shaped irregularity.

(3) In the vibration source of each of the above-described embodiments, piezoelectric elements such as piezoelectric ceramics are arranged in an annular shape, but an appropriate number of piezoelectric elements may be attached to the vibrating body.

(4) In each of the above-described embodiments, the piezoelectric ceramic is shown as the excitation source, but a magnetostrictive oscillator or the like may be used. Further, the vibrating body may be vibrated by using a permanent magnet or an electromagnetic magnet.

(5) In each of the above-mentioned embodiments, the extract bodies are located in the even-numbered or odd-numbered quarter wavelength sections and are arranged at 1/2 wavelength intervals. However, it is not always necessary to arrange at intervals of ½ wavelength, and for example, as shown in FIG. 13, the interval P of the extraction bodies 269 provided on the vibrating body 263 may be set for each wavelength λ. Further, the extract bodies 269 may not be provided at equal intervals except for problems such as efficiency. That is, irregular intervals may be used.

(6) As shown in FIG. 14, it is desirable that the extractor 279 on the surface of the vibrating body 273 is provided in a portion that does not include the node N and the antinode L in the quarter wavelength section of the standing wave in principle. As shown by 279 ', a shape slightly protruding to the belly L (or node N) is also allowed. Of course, in this case, the protruding portion from the belly L or the node N becomes a loss.

(7) The extract 289 in FIG. 15 partially protrudes from the predetermined quarter wavelength section, but of course, this structure is included in the concept of the present invention. That is, in the extractor 289, the coupling portion C with the vibrating body 283 may be substantially 1/4 wavelength or less.
This structure may be effective because the contact area with the contact body that contacts the extract body 289 is increased and the frictional force is increased.

(8) In the above-described embodiment, the piezoelectric element of the vibration source is divided into two sections, and each of them is polarized in the opposite direction for every ½ wavelength so that the contact body is normally and reversely rotated. Alternatively, the position of the extractor may be changed separately, and the position of the extractor may be changed by operating a selection means such as a lever to rotate the extractor forward and backward.

(9) In the second and third embodiments, the extractor and the contactor are two.
Although provided in rows, it is also possible to provide three or more rows of extractors having different widths and positions and rotate one or more contact bodies in three or more speeds or in different directions.

(10) Although the ultrasonic motor is shown as the forward / reverse rotation driving device in the above-mentioned embodiment, the focus adjustment of the autofocus camera, the electronic products such as the tape recorder and the floppy disk driving device which use the magnetic recording medium, the industrial robot and the work machine. It can also be applied to precision positioning devices such as machines.

Further, the forward / reverse rotation driving device does not necessarily have to include the contact body, and the extract body may be brought into contact with the paper, the card, the object that needs to be moved, or the like.

Therefore, in this case, the paper or the card corresponds to the contact body.
Therefore, it can be applied to a paper feeding device, a card feeding device, and the like.

〔The invention's effect〕

The present invention relates to a vibration source that generates a vibration of a specific frequency, an annular vibration body that is excited by the vibration source and has a length that is an integral multiple of the wavelength of the vibration generated by the vibration source, and that is generated in this vibration body. The contact body is provided between the node and the antinode of the standing wave in contact with the vibrating body and the contact body, and selects the motion component in the nodal direction from the antinode of the standing wave generated in the vibrating body. A forward-reverse rotation driving device for rotating the contact body in forward and reverse directions relative to the vibrating body, the extractor transmitting the contact to the vibrating body and the extractor for selectively switching the direction of the motion component selected by the extractor. In the above, the extractor is provided in a plurality of rows with respect to the vibrating body, the contact body is provided for each row with respect to the plurality of rows of extractors, and the extractor is provided at an arbitrary position in each row. Provided, the width in the moving direction of the vibrating body side base is arbitrary for each row Since it is set, it is possible to rotate forward and backward a plurality of contact members, it is possible to set the moving speed and the driving force for each contact member.

[Brief description of drawings]

1 to 4 are views for explaining the principle of the present invention, and FIGS. 1 and 2 (A) and (B) show the rotation direction of the roller when the elastic body is excited by a standing wave. FIG. 3 and FIG. 4 are explanatory diagrams of the positional relationship, and are waveform charts showing the vibration pattern of standing waves. 5 to 8 are views showing the first embodiment of the present invention. 9 and 10 are diagrams showing a second embodiment of the present invention. 11 and 12 are diagrams showing a third embodiment of the present invention. 13 to 15 are views showing modifications of the present invention. 80 …… Vibrator, 81 …… Vibration source, 83 …… Extractor, 84 …… Contact body, 86 …… High frequency power supply, 87 …… Switch, 110 …… Vibrator, 113a, 113b …… Extractor, 114a , 114b …… Contact, 24
1,242 …… contact body, 243 …… vibrating body, 249,250 …… extractor

Claims (1)

[Claims] 1. A vibration source that generates vibration of a specific frequency, an annular vibration body that is excited by the vibration source and has a length that is an integral multiple of the wavelength of the vibration generated by the vibration source, and the vibration body. The standing wave generated is provided between the node and the antinode in contact with the vibrating body and the contact body, and the contact component is selected by selecting a motion component in the nodal direction from the antinode of the standing wave generated in the vibrating body. A forward / reverse rotation drive for rotating the contact body forward / reverse relative to the vibrating body, having an extractor transmitted to the body and a selecting means for selectively switching the direction of the motion component selected by the extractor. In the device, the extractor is provided in a plurality of rows with respect to the vibrating body, the contact body is provided for each row with respect to the plurality of rows of extractors, and the extractor is at any position in each row. The width in the moving direction of the vibrator side base is set for each row. Normal and reverse rotation drive device, characterized in that it is set to.