JPH07106071B2 - Ultrasonic motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultrasonic motor, and more particularly to an ultrasonic motor that applies an electric signal in an ultrasonic region to a piezoelectric element to operate as a uniaxial actuator. is there.

[Prior Art] FIGS. 11 and 12 show a conventional ultrasonic motor proposed by the present inventor, which is a disk-shaped base body (21) made of an elastic body such as metal.
A through hole (21a) that functions as a driver is provided at the center of the. Further, piezoelectric elements (23) and (24) for generating vibrations in a disc bending mode and a radial mode are fixed to both side surfaces of the base body (21). A slider (22) is engaged with the through hole (21a).

With the above configuration, when an electric signal in the ultrasonic range is applied to each of the piezoelectric elements (23) or (24), the base body (21)
Generates both disk bending mode and radial mode vibrations simultaneously. Therefore, the combined vibration of both components is generated in the through hole (21a).

The slider (22) is pressed against the through hole (21a), and when the substrate (21) is excited by the piezoelectric element (23) or (24), the slider (22) moves left and right in the central axis direction. To be done.

In this way, the sliders (22) that are driven bodies can be given arbitrary linear movements in opposite directions.

[Problems to be Solved by the Invention] The conventional ultrasonic motor as described above has a large diameter in order to be of a high output type. Therefore, the space factor is poor, and it is difficult to support the slider. There was a problem.

The present invention is intended to solve the above problems, and an object thereof is to obtain an ultrasonic motor capable of achieving a large output, a small space, and an increase in the durability of a slider.

[Means for Solving the Problems] An ultrasonic motor according to the present invention is provided with a plurality of two groups of piezoelectric elements at centrally symmetrical positions on the outer surface of a rectangular tubular base, and at the center of the inner wall surface of each cylinder. By placing the driver elements at equal distances so as to face each other and applying an electric signal in the ultrasonic region for each group of piezoelectric elements, a composite resonance of the flow direction expansion / contraction mode and the tube mouth opening / closing bending mode is generated in the substrate.

[Operation] In the present invention, the moving body pressed against the driver is shaken in the longitudinal direction in response to the vibration in the flow direction expansion / contraction mode of the base body, and the pressure contact / separation is caused due to the bending mode vibration. Repeat the release. As a result, the movable body is linearly moved in the longitudinal direction.

[Embodiment] FIG. 1 to FIG. 3 show an embodiment of the present invention, in which the same poles are polarized substantially in central symmetry on the four outer surfaces of a square tubular substrate (1). Piezoelectric elements (2a), (2
b), (3a), (3b), (4a), (4b) and (5a),
(5b) is stuck.

On the inner wall surface of the base body (1), a pair of opposing driver elements (6a),
(6b), (7a), and (7b) are installed at equal distances from the center and offset from each other by 90 °. (8a) and (8b) are mounting holes.

In order to avoid complications, the sliders, which are the movable bodies to be pressed against the driver elements (6a), (6b) and (7a), (7b), and the electrodes and connection leads provided on each piezoelectric element are not shown in the drawing. Omitted.

Next, the operation will be described.

The substrate (1) has a first group of piezoelectric elements (2a), (2b),
(3a), (3b) and the second group of piezoelectric elements (4a), (4b),
With the excitation by (5a) and (5b), the longitudinal stretching mode,
Both vibrations of the rectangular cylinder alternating open / close bending mode are generated at the same time.

In this embodiment, the first group of piezoelectric elements (2a), (2b),
(3a), (3b) or the second group of piezoelectric elements (4a), (4
When an ultrasonic signal is applied to each of b), (5a), and (5b), the base body (1) has an alternating open / close mode shown by a solid line and a broken line in FIG. It is formed in a dimensional relationship in which modes are generated at the same time and complex resonance occurs.

The solid line and the broken line in FIG. 4 show the opening / closing manner associated with the vibration in each half cycle, and since the base body (1) is a square tube, the movement of each facing surface is center symmetric.

Now, the first group of piezoelectric elements (2a), (2b), (3a), (3
Looking at the operation of the substrate (1) when an electric signal is applied to the b) side, since the piezoelectric elements are all the same in polarization, the lengthwise expansion / contraction mode is the fundamental wave, as shown by the solid line in FIG. , The piezoelectric element surface to which a voltage is applied at the same time as extending in the longitudinal direction also opens outward in the vertical direction, so that the horizontal surface, that is, the second group of piezoelectric elements (4a), (4b), (5a), (5b The surface with) shrinks in the opposite direction and closes inward. Therefore, the driver elements (7a) and (7b) installed on the right half side further contact the slider, which is the movable body, and apply a force to the right.

In the next half cycle, the opposite behavior occurs, so
As shown by the broken line in the figure and Fig. 5, this time the surface with the piezoelectric elements (2a), (2b), (3a) and (3b) of the first group closes and shrinks. The driver (6
Since a) and (6b) are pressed against the slider, a rightward force is applied as in the direction of the broken arrow on the left side, which is the installation position of the drivers (6a) and (6b). Thus, the slider is 1
Both positive and negative of the cycle will be moved to the right.

Next, the slider is moved to the left by switching to the piezoelectric element (4a), (4b), (5a), (5b) side of the second power feeding group. That is, since the polarization directions of the piezoelectric elements are all the same, only the open / close bending mode is reversed while the lengthwise mode of FIG. 5 remains the same. Therefore, the movement of the slider to the left is achieved.

As described above, the driver elements (6a), (6b) and (7a), (7b)
The moving direction of the slider pressed against the
Since the power supply is switched to one group, the oscillation drive circuit can be extremely simple. Generally, a self-exciting circuit that detects the impedance change at the resonance point and oscillates,
A self-excited circuit that feedbacks using the voltage generated from one of the two piezoelectric element groups is adopted.

Since all the piezoelectric elements have the same polarity, a single plate may be attached without separating them on the left and right.

Specific numerical examples of the above examples are: dimensions of the base (square tube): length 120 mm, tube opening 20 x 20 mm 〃 wall thickness: 2.5 mm, aluminum material piezoelectric element thickness: 0.4 mm, PZTHQ material drive Thickness of child: 0.1 mm, zirconia porcelain Slider material: Polyetheretherketone material Resonance frequency: 19.05 kHz Driving voltage: 5 V RMS value, slider speed: 500 mm / sec (no load) was obtained.

When it is desired to drive at a lower voltage, two piezoelectric elements may be stacked and arranged in parallel. Further, the piezoelectric element can be installed on the inner wall of the base. Further, the driver may be installed on the outer surface of the substrate, or on either one of the left and right sides.

Further, the connection to the piezoelectric element can be crossed left and right. That is, piezoelectric elements (2a), (2b), (5a), (5b)
Is the first group, and the piezoelectric elements (3a), (3b), (4a), (4
If b) is the second group and the connection is made by twisting 90 ° right and left, the behavior of the substrate (1) is as shown in Fig. 6, and the polarization is the same, so the length mode is the same as described on the left. Occurs,
The left and right open / close modes are reversed. In this case, the driver installation surface is the same inner wall surface of the base body on both the left and right sides.

Further, the pressure inoculation of the slider driver can be performed by sandwiching the rubber sheet.

Further, the substrate itself may be composed of a piezoelectric ceramic. At this time, if an elastic plate or another piezoelectric ceramic plate is attached to generate the bending mode, the width of the manufacturing method can be further expanded. When only the piezoelectric ceramic is used, it may be cylindrical.

In the above embodiments, the case of the rectangular tube is described, but the operation is the same even if the outer surface is square and the inner cross section is circular.

The length mode is not limited to the fundamental wave, and can be combined with the resonance of higher harmonic waves.

The cylindrical shape of the base body (1) is not limited to a quadrangle, but is the same for hexagons, octagons, and other even-numbered polygons. Even in the large size, various types can be designed by combining with the length higher mode.

As an example in which the base body (1) is a polygonal cylinder, a case where the outer shape is hexagonal and the inner side is round is shown in FIGS. 7 to 9. Since the second harmonic is used for the length mode, the polarization (shown in the figure) is different between the left and right, and the connection of each group is picked up by three piezoelectric elements and shifted by one on the left and right.

That is, piezoelectric elements (9a), (9b), (9c) and (10a), (10b), (10c) are applied to the first group, and piezoelectric elements (11a), (11b), and (11c) and (12a), (12b), (1
By filling 2c), the slider set in the center hole of the base body (1) can be arbitrarily moved in the left-right direction.

By changing the connections in FIG. 7, the piezoelectric elements (9a), (9
b), (9c) and (12a), (12b), (12c), the second group includes piezoelectric elements (11a), (11b), (11c) and (10a), (10a).
It may be b) or (10c). In this case, the installation of the driver is different on the left and right.

Further, as a structure for generating a large thrust, as shown in FIG. 10, ring-shaped piezoelectric elements (13a), (13b) and a ring-shaped piezoelectric element (13a) are provided on the nodes of the base (1) consisting of two polygonal cylinders (1a) (1b). It is conceivable to hold the length mode terminal (14) and tighten it with a bolt (15) to form a Langevin structure. (16a), (1
6b) is a driver.

With such a configuration, the phase on the length mode side can be adjusted, so that a larger thrust can be generated.

Here, in the ultrasonic motor of the present invention, since the slider and the outer motor move relative to each other by the ball screw, it goes without saying that either one may be selected on the fixed side.

EFFECTS OF THE INVENTION As is apparent from the above description, according to the present invention, a plurality of driving piezoelectric elements are fixed to the outer surface of a rectangular tube-shaped base to excite the base, and a vibration mode in the longitudinal direction is obtained. By simultaneously generating the opening and closing bending mode of the tube mouth, the slider is linearly moved by the driver provided in the rectangular tube.
The direction of the slider can be switched only by switching the power supply to the piezoelectric element, the electric circuit can be simplified, and high output conversion and space saving can be achieved.

[Brief description of drawings]

FIG. 1 is a side view of an embodiment of the present invention, and FIGS. 2 and 3 are sectional views taken along planes II-II and III-III of FIG. 1, respectively, and FIGS. FIGS. 6 and 6 are schematic diagrams for explaining the operation of the embodiment, FIG. 7 is a side view of another embodiment, and FIGS. 8 and 9 are the left front view and the right view of FIG. 7, respectively. A front view, FIG. 10 is a side sectional view of still another embodiment, FIG. 11 is a front view of a conventional ultrasonic motor, and FIG. 12 is a side sectional view of the same. (1) …… Substrate, (2a), (2b)… (5a), (5b) ……
Piezoelectric element, (6a), (6b), (7a), (7b) ... Driver.

Claims (1)

[Claims] 1. A base body made of a rectangular tube-shaped elastic body, two groups of piezoelectric elements each fixed to the surface of the base body and having a plurality of electric signals applied to an ultrasonic region, and an inner wall surface of the base body. An ultrasonic motor having a plurality of driver elements provided facing each other at equal distances from the center of the base body, and causing a composite resonance of a flow direction expansion / contraction mode and a barrel opening / closing bending mode in the base body.