JPH0667232B2 - Bidirectional drive - Google Patents

Description

The present invention relates to a linear ultrasonic motor (vibration wave motor).
A bidirectional drive device driven by a standing wave applicable to the above.

[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 superposition of 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 provides a bidirectional drive device capable of efficiently converting a standing wave applied to a vibrating body into a two-way motion based on a principle different from the conventional method using a traveling wave and the vibration synthesis method. The purpose is to

[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, standing waves have movement abilities in different directions, and it is possible to move an object in a particular direction by selecting only the movement abilities in that particular direction. Do you get it.

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 an extractor having a vibrating end and selecting a motion component in the node direction from the antinode of the standing wave between the node and the antinode of the standing wave generated in the vibrating body excited by the vibration source. When the extractor is positioned, the direction of the motion component selected by the extractor is selectively switched by the selecting means, the motion component selected by the extractor is transmitted to the contact body, and the contact body and the vibrating body are relatively driven in two directions. It was done like this.

[Principle of Invention]

As mentioned above, the standing wave has a partially different motion ability in different directions, and the inventor has learned that an object can be rotated or moved by selecting only the motion ability in that specific direction. The experiment will be described.

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 formula of 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 λ = 26.9 [mm].

Comparing this value 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 X-direction component vibration as in the case of a 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.

Assuming the above results, consider the case where a traveling wave is vibrated in an annular elastic body, and consider the above results. 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-sinωt-coskx-e-A-k-sin (ωt + π / 2) -cos (kx + π /
2) = -e · A · k · sin (ωt−kx) Y component at an arbitrary point; Asinωt · sinkx + Asin (ωt + π / 2) · sin (kx + π / 2) = Acos (ωt−kx) Even if an equation is assumed as a wave, the synthesis of traveling waves by two types of standing waves is explained, and the equation is considered to be close to 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 ultrasonic vibration is extremely large. It also appears in the phenomenon of friction reduction due to vibration.

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] An ultrasonic motor of this embodiment has two types of standing waves Sa and Sb in a vibrating body (for example, a rod-shaped elastic body) 100 having an end as shown in FIGS. 5 and 6. Is generated so that the contact body (for example, a slider) 104 can be selectively driven to travel in the left-right (front-back) direction in the drawing.

In order to generate these two types of standing waves Sa and Sb, first and second vibration sources (for example, piezoelectric elements such as piezoelectric ceramics) 10
1a and 101b are attached to both surfaces (upper and lower surfaces in the figure) of one end of the vibrating body 100 in one direction, and the first vibration source 101a is a high-frequency power source.
106a and a selection means such as a switch 107a are connected, and a high frequency power source 106b and a selection means such as a switch 107b are connected to the second vibration source 101b.

It should be noted that the pitch Pb between the piezoelectric elements forming the second vibration source 101b is arranged in parallel.
Is set to be twice the parallel arrangement interval Pa of the piezoelectric elements of the first vibration source 101a.

The vibrating body 100 is made of a metal such as brass or aluminum, and the vibrating portion has a length that is an integral multiple of 1/2 wavelength, and is located between the node of the standing wave and the antinode (between 1/4 wavelength). A region for every odd or even multiple of ¼ wavelength, for example, one wavelength for the standing wave Sa for leftward movement, and one for the standing wave Sb for rightward movement.
The extractor (for example, a convex portion such as a protrusion) 103 is provided so as to have an interval of / 2 wavelengths. The width of the extractor 103 is not more than 1/4 wavelength of the standing wave.

The installation interval Pc of the extractor 103 is approximately equal to the interval of the wavelength λa of the first standing wave Sa generated by the first vibration source 101a.
That is, λ of the first standing wave Sa generated by the first vibration source 101a
/ 4 section is odd-numbered section a1 and the second standing wave
The extractor 103 is provided so as to be located at even-numbered positions b2 and b4 of Sb.

The contact body 104 is formed of a synthetic resin such as acrylic or a metal plate, and is in pressure contact with the extractor 103.

Therefore, when the switch 107a is turned on by oscillating the first power supply 106a having the first oscillation frequency, the first vibration source 101a is excited and the first standing wave Sa is generated in the vibrating body 100. As a result, the extraction body 103 extracts the amplitude motion of the first standing wave Sa in the odd-numbered section a1, so that the contact body 104 travels leftward in the drawing.

On the other hand, when the second power supply 106b having the second oscillation frequency is oscillated to turn on the switch 107b, the first vibration source 101b is excited and the second standing wave Sb is generated in the vibrating body 100. For this reason, since the extractor 103 is amplitude-moved by the even-numbered b2 and b4 of the second standing wave Sb, the contact body 104 moves to the right in the figure.

In this way, the two vibration sources 101a, 10 having a wavelength relationship of 1: 2
By selectively controlling 1b, the contact body 104 can be run in any direction.

According to the embodiment described above, while generating a standing wave in the vibrating body 100 by reflecting the vibration wave at the end of the vibrating body 100,
Since the extraction body 103 that selects the motion component in the node direction from the antinode of the standing wave is positioned between the node and the antinode of the standing wave, it is not necessary to provide an energy feedback system for the vibration wave in the vibrating body 100. The contact body 104 can be efficiently driven by the standing wave with a simple structure.

Further, vibration sources 101a and 101b, which are composed of two piezoelectric bodies that are polarized in opposite directions for each 1/2 wavelength, which excite two types of standing waves having a wavelength of 1: 2, are provided, and switches 107a and 107b are used. Since the two vibration sources 101a and 101b are selectively energized, the contact body 104 can be moved left and right (forward and backward) without changing the position of the extraction body 103.

[Second Embodiment] The ultrasonic motor of FIG. 7 uses the same vibration source and selection means as in the first embodiment to move the two contact bodies 124a, 124b left and right at different speeds. It was done.

This motor has the first and
Although the second extractors 123a and 123b are provided, the widths of the extractors in each row in the length direction of the vibrating body 120 are different. Accordingly, the extractors 123a and 123b have different momentums given by the contact bodies 124a and 124b, respectively, so that the traveling speeds of the contact bodies 124a and 124b are different.

In addition, as shown in FIG. 8, the first extractor 133a has the same width as the extractors 133a and 133b and is arranged in the same λ / 4 section.
Can be provided at a position near the node N, and the second extractor 133b can be provided at a position near the belly L. In this motor, the horizontal motion vector of each extractor is different, so
The traveling speeds of the second contact bodies 134a and 134b are different.

Although only two rows of extractors and contact bodies are provided, three or more rows of extractors having different widths and positions may be provided to drive one or a plurality of contact bodies at three or more speeds.

[Third Embodiment] FIG. 9 uses a roller 43 as an extractor, which is held by a retainer 45 at intervals of λ / 2. This is a vibrating body 40
The standing wave energy of is transmitted to the contact body 44 via the roller 43 and linearly drives the contact body 44. In this embodiment, by moving the roller 43 by approximately λ / 4 in the length direction of the vibrating body 40, the movement direction of the contact body 44 can be reversed.

That is, the roller 43 is moved in the length direction of the vibrating body 40 by approximately λ / 4 so that the roller 43 in the λ / 4 section a2 in FIG. 2 is moved to the position 43 ′ in the first λ / 4 section a1. Then, all the rollers 43 move from the even λ / 4 section to the odd λ / 4 section.
Move to section / 4. As a result, the contact body moving in the f direction moves in the f'direction.

[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 the above embodiment, the example in which the contact body in contact with the extract body moves has been described, but the contact body may be fixed and the vibrating body may move. That is, it is sufficient that the vibrating body and the contact body move relative to each other.

(2) Although the convex portion and the roller are shown as the extractor, they may be corrugated irregularities.

(3) In the above-mentioned embodiment, the extract bodies are positioned in the even-numbered or odd-numbered quarter-wavelength sections and are arranged at 1 / 2-wavelength intervals. However, if the even-numbered or odd-numbered rule is met, It is not always necessary to arrange at intervals of ½ wavelength, and for example, as shown in FIG. 10, 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.

(4) As shown in FIG. 11, in principle, the extractor 279 on the surface of the vibrating body 273 is preferably provided in a portion that does not include the node N and the antinode L in the quarter wavelength section of the standing wave. 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.

(5) A part of the extractor 289 of FIG. 12 protrudes from a predetermined quarter wavelength section, but of course, this structure is included in the idea 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.

(6) Although the Langevin oscillator or the piezoelectric ceramic is shown as the excitation source in the above embodiment, 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.

(7) Although the ultrasonic motor is shown as the bidirectional driving device in the above-described embodiment, focus adjustment of an autofocus camera, electronic products using magnetic recording media such as tape recorders and floppy disk driving devices, industrial robots, machine tools, etc. It can also be applied to the precision positioning device of.

Further, the bidirectional 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〕

This invention has a vibrating source that generates a vibration of a specific frequency, a vibrating body that has a vibrating end, and is excited by this vibrating source, and the vibration between a node and an antinode of a standing wave that is generated in the vibrating body. An extractor, which is provided in contact with the body and the contact body, selects the motion component in the node direction from the antinode of the standing wave generated in the vibrating body and transmits it to the contact body, and the motion selected by the extractor. In a bidirectional driving device provided with a selection means for selectively switching the direction of the component, the vibration source excites two types of standing waves having a wavelength of 1: 2 and is polarized in opposite directions for each 1/2 wavelength. In addition to the above two piezoelectric bodies, the selection means is means for selectively energizing the two piezoelectric bodies, so that the contact body is moved relative to the vibrating body without changing the position of the extraction body. Can be moved in any direction.

[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 and 6 are views showing the first embodiment of the present invention. 7 and 8 are views showing a second embodiment of the present invention. FIG. 9 is a diagram showing a third embodiment of the present invention. 10 to 12 are views showing a modified example of the present invention. 100 ... Vibrator, 101a, 101b ... Vibration source, 103 ... Extractor, 104 ... Contact body, 106a, 106b ... High frequency power source, 107a, 1
07b …… Switch

Claims (5)

[Claims] 1. A vibrating body having a vibrating source for vibrating at a specific frequency, a vibrating end, and excited by the vibrating source, and a node of a standing wave generated in the vibrating body and an antinode. An extractor, which is provided in contact with the vibrating body and the contact body, selects the motion component of the standing wave generated in the vibrating body from the antinode to the node direction and transmits the motion component to the contact body, and the extractor. In a bidirectional driving device having a selecting means for selectively switching the direction of a motion component, the vibration source excites two types of standing waves with a wavelength of 1: 2 A bidirectional drive device comprising two polarized piezoelectric bodies, and the selecting means is means for selectively energizing the two piezoelectric bodies. 2. The bidirectional driving device according to claim 1, wherein the extractor is an odd-numbered or even-numbered arbitrary one of quarter wavelength sections obtained by dividing the wavelength of the standing wave into four equal parts. A bidirectional drive device characterized by being provided in a region. 3. The bidirectional drive device according to claim 1, wherein the extractors are provided in a plurality of rows with respect to the vibrating body, and the contact bodies are provided for each row with respect to the plurality of rows of extractors. A bidirectional drive device characterized by being provided. 4. The bidirectional drive device according to claim 3, wherein the extractor is provided at an arbitrary position for each row. 5. The bidirectional drive device according to claim 3, wherein the extractor has a width in the moving direction of the vibrating body side base portion set arbitrarily for each row.