JP3356790B2 - Ultrasonic linear motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic linear motor driven along a bar by using ultrasonic vibration as a driving source.

[0002]

2. Description of the Related Art A conventional ultrasonic linear motor is disclosed in
As described in JP-A-2-30297, a method is used in which a vibrating surface is pressed against a certain member and a pressing force is applied to the pressing surface and the vibrating surface.

[0003]

In the above prior art, a pressing spring and a bearing mechanism for sliding are required to press the vibrating surface against a certain member, which hinders downsizing of the linear motor. There was a problem that the cost was high. An object of the present invention is to provide a small and inexpensive ultrasonic linear motor using an ultrasonic linear motor that drives the outer peripheral surface of a bar.

[0004]

In order to achieve the above object, an ultrasonic linear motor according to the present invention comprises a plurality of first piezoelectric elements which can be driven independently of each other and vibrate in parallel with the traveling direction. A second axis that penetrates the first piezoelectric element in parallel with the traveling direction and a second axis vibrating perpendicularly to the traveling direction, the second piezoelectric element being arranged to be able to grip the axis with the plurality of first piezoelectric elements interposed therebetween; A piezoelectric element, wherein a gap is set in the radial direction between the first piezoelectric element and the shaft, and the second piezoelectric element has an interference against the outer diameter of the shaft when contracting, and a gap when expanding. The driving speed is changed by changing a phase difference of an AC voltage applied to each of the plurality of first piezoelectric elements.

The operation of the present invention is similar to that of a person climbing a pole. First, one of the second piezoelectric elements grips the axis, and the other does not. In this state, the central first piezoelectric element is extended in the traveling direction. Next, the second piezoelectric element is gripped,
Do the reverse by not grasping, and in this state,
Let's shrink the piezoelectric element. By the above operation, the first piezoelectric element at the center is moved by the amount of extension. By repeating this, linear driving is realized.

Further, since the plurality of first piezoelectric elements can be driven independently of each other, the driving speed can be changed by applying alternating voltages having different phases to the piezoelectric elements.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the background art of the present invention will be described with reference to FIG.

FIG. 1 shows an example in which a round bar is used as the bar 1. Ring-shaped piezoelectric elements 3 and 4 vibrate in the radial direction so as to surround the bar 1, and a ring-shaped piezoelectric element vibrating in the axial direction of the bar 1. The element 2 and an intermediate ring 5a, 5b sandwiched between the three piezoelectric elements 2, 3, 4 are integrally formed.
The inner diameters of the piezoelectric elements 3 and 4 are set so as to have an interference with the outer diameter of the rod 1 when contracting and a gap when expanding. The piezoelectric element 2 and the intermediate rings 5a and 5b are
And a gap in the radial direction.

In FIG. 1 having such a configuration, a case where the bar 1 is driven from left to right on the drawing will be described. First, the piezoelectric element 3 sandwiches the bar 1 in a contracted state. The piezoelectric element 4 has a gap with the bar 1 in an expanded state. At this time, when the piezoelectric element 2 is expanded, the expanded piezoelectric element 4 moves to the right. Next, the piezoelectric element 4 is set to the contracted state, and the piezoelectric element 3 is switched to the expanded state. At this time, when the piezoelectric element 2 is in a contracted state, the contracted amount, that is, the expanded piezoelectric element 2 moves to the right. By the above operation, the piezoelectric elements 2, 3, 4 and the intermediate ring 5a,
5b is moved by the amount of displacement of the piezoelectric element 2, and this operation is repeated by driving the piezoelectric elements 2, 3, and 4 with an appropriate phase difference, thereby realizing high-speed linear driving. FIG. 2 is an example of an AC voltage applied to the piezoelectric elements 2, 3, and 4 in FIG. 1. A curve 6 is a voltage applied to the piezoelectric element 3, a curve 7 is a voltage applied to the piezoelectric element 4, and a curve 8 is a voltage applied to the piezoelectric element 2. Is shown. Since the curves 6 and 7 have opposite polarities, the piezoelectric elements 3 and 4 operated thereby
When one is inflated, the other is contracted, and conversely, when one is contracted, the other is expanded. When the voltage of the curve 8 is applied to the piezoelectric element 2 here, since the voltage has the same polarity as the voltage applied to the piezoelectric element 4, the operation described in FIG. 1 is repeated. In order to change the driving direction from right to left in FIG. 1, the vibration phase of the piezoelectric element 2 may be changed by 180 °. That is, the curve 8 may be reversed. Next, an embodiment of the present invention will be described with reference to FIG.

FIG. 3 shows an example in which the piezoelectric elements 2 vibrating in the axial direction in FIG. 1 are increased in two pairs, and the piezoelectric elements 9 and 10 are used for the vibration in the axial direction. The basic operation is the same as that of FIG. 1, but since two pairs of piezoelectric elements 9 and 10 are used in the axial direction, the displacement amount becomes large, and higher-speed driving can be realized.
Further, the driving speed can be changed by shifting the phase of the vibration of the piezoelectric elements 9 and 10. This will be described with reference to the drawings. A curve 11 in FIG. 4 indicates a voltage applied to the piezoelectric element 9, and a curve 12 indicates a voltage applied to the piezoelectric element 10. The sum of the displacements of the piezoelectric elements 9 and 10 is represented by a curve 13 and a curve 1
In FIG. 4 where there is no phase difference between 1 and 12, the maximum displacement can be obtained. Next, FIG. 5 shows a curve 1 of a voltage applied to the piezoelectric element 9.
When the phases of the curve 4 and the voltage curve 15 applied to the piezoelectric element 10 are shifted in phase, the curve 16 indicating the total displacement of the piezoelectric element 9 and the piezoelectric element 10 has a smaller amplitude than the curve 13 in FIG. You can see that. As a result, the driving speed also decreases, and it can be seen that the driving speed can be changed by changing the phase of the voltage applied to the piezoelectric elements 9 and 10. In both the example of FIG. 1 and the example of FIG. 3, a stacked piezoelectric element may be used for the piezoelectric elements 2, 3, 4, 9, and 10 in order to obtain a larger displacement.

[0010]

According to the present invention, an ultrasonic linear motor can be constituted only by a driving section composed of a first piezoelectric element, a shaft penetrating the first piezoelectric element, and a second piezoelectric element. There is no need for a pressure spring and a bearing mechanism for sliding, and there is an effect that a small and inexpensive ultrasonic linear motor can be obtained. Furthermore, the driving direction and the driving speed can be changed only by changing the phase of the driving voltage, and there is an effect that an ultrasonic linear motor having excellent controllability can be obtained.

Further, for example, the first piezoelectric element is stopped while being vibrated by applying an AC voltage having a voltage such that the vibration amplitudes of the two first piezoelectric elements become the same and of opposite phases. Can be. Therefore, in order to shift from the stop state to the drive state, it is possible to shift to the drive state in a short time only by changing the phase, and it is possible to reduce the control error because the drive is not stopped once. Further, since the gap is set between the first piezoelectric element and the shaft, there is an effect that even if the first piezoelectric element is stopped while being vibrated, neither the first piezoelectric element nor the shaft is worn.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a background art of the present invention.

FIG. 2 is a diagram showing driving voltages and displacements according to the background art of FIG. 1;

FIG. 3 is a perspective view showing an embodiment of the present invention.

FIG. 4 is a diagram showing a drive voltage and a displacement according to the embodiment of the present invention.

FIG. 5 is a diagram showing a drive voltage and a displacement according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bar material 2 Piezoelectric element 3 Piezoelectric element 4 Piezoelectric element 5a Intermediate ring 5b Intermediate ring 6 Curve 7 Curve 8 Curve 9 Piezoelectric element 10 Piezoelectric element 11 Curve 12 Curve 13 Curve 14 Curve 15 Curve 16 Curve

Continuation of the front page (56) References JP-A-60-217415 (JP, A) JP-A-3-49574 (JP, A) JP-A-3-49575 (JP, A) JP-A-2-209336 (JP) JP-A-63-1384 (JP, A) JP-A-58-93477 (JP, A) JP-A-2-114869 (JP, A) JP-A-2-30297 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H02N 2/00

Claims (1)

(57) [Claims] 1. A plurality of first piezoelectric elements that can be driven independently of each other and vibrate in parallel with the traveling direction, an axis that passes through the first piezoelectric element in parallel with the traveling direction, and the plurality of piezoelectric elements. A second piezoelectric element disposed so as to be able to grip the shaft with the first piezoelectric element interposed therebetween and vibrating perpendicularly to the traveling direction, wherein the first piezoelectric element and the shaft are arranged in a radial direction. A gap is set in the second piezoelectric element, and the second piezoelectric element is set so as to have an interference when contracting and a gap when expanding with respect to the outer diameter of the shaft, and the AC applied to each of the plurality of first piezoelectric elements. An ultrasonic linear motor, wherein a driving speed is changed by changing a phase difference of a voltage.