JPH0246183A - Ultrasonic linear motor - Google Patents

Abstract

PURPOSE:To improve efficiency and to reduce the dimension by providing a beam of the second elastic body to a free end of the cantilever of the elastic body, by sticking a piezoelectric body to one surface of the beam and by applying AC electric field there. CONSTITUTION:In an oscillator 30 of an ultrasonic linear motor the 1st cantilever 18 is constituted by sticking a piezoelectric body 17 to one surface of an electric body 16. An end of this cantilever 18 is fixed by a fixture 21 and to the other end an end of the 2nd cantilever 19 is secured to constitute the oscillator 30. When AC electric field is applied to the piezoelectric body 17, the 1st beam 18 generates flexural oscillation as shown in the figure, where the tip of the 1st beam 18 sets up a motion of a locus S1 and the tip of the 2nd beam 19 sets up a motion of a locus S2, so that the effective component of transverse displacement of mechanical output is extended from X1 to X2. The oscillator 30, of which an end is fixed by a fixture 31, is thus provided through bearings 32 between the fixture 31 and a rail 34, and by applying the above electric field, the oscillator 30 moves towards an arrowhead B along the rail 34.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an ultrasonic linear motor that generates driving force using elastic vibrations produced by a piezoelectric body.

2. Description of the Related Art In recent years, ultrasonic linear motors have attracted attention in which elastic vibrations are excited in a moving body made of a piezoelectric material such as a piezoelectric ceramic, and this is used as a driving force.

Hereinafter, the conventional technology of ultrasonic linear motors will be explained with reference to the drawings.

FIG. 4 is a general view of an ultrasonic linear motor, in which a vibrating body 5 is constructed by sandwiching and fixing disk expansion piezoelectric bodies 1 and 2 between cylindrical elastic bodies 3 and 4. Piezoelectric material
When an alternating current electric field near the resonant frequency of the vibrating body 5 is applied to the vibrating body 5 and 2, the vibrating body 5 vibrates vertically in a longitudinal vibration mode, as shown by the arrow in the figure.

The mechanical impedance seen from the imaging surface of the vibrating body 5 is impedance-converted by the horn 6, and matched to the mechanical impedance for deflection imaging of the transmission rod 7. The tip of the horn 6 is acoustically coupled to a portion of the transmission rod 7 near one end. Therefore, the vertical vibration of the vibrating body 5 is efficiently transmitted to the transmission rod 7 by the horn 6, and the transmission rod 7 bends and vibrates. This bending vibration progresses from one end of the transmission rod 7 to the other end.

In a part near the other end of the transmission rod 7, the horn 8 is connected as in the one end.
The tips of the two are acoustically coupled. A vibrating body 13, which is exactly the same as the vibrating body 5, is constructed by sandwiching and fixing the disc carving electric bodies 9 and 10 between cylindrical elastic bodies 11 and 12. This vibrating body 13 is connected to the horn 8. Therefore, the bending vibration that has progressed from one end of the transmission rod toward the other end is transmitted to the vibrating body 13 by the horn 8, and is converted into vertical motion of the vibrating body 13. A load R with impedance matching is connected to the piezoelectric bodies 9 and 10, and the above-mentioned vertical vibration is consumed by the load R. Therefore,
In the transmission rod 7, bending vibration exists only as a traveling wave.

A moving body 14 is driven by the bending vibration traveling through the transmission rod 7, and moves in a direction opposite to the traveling direction of the traveling wave. In the above description, the moving direction of the moving body 14 is assumed to be one direction, but if the driving end is reversed, the moving body 14 also moves in the opposite direction.

FIG. 5 shows the principle by which a traveling elastic wave of deflection drives a moving body. Due to the bending vibration of the transmission rod 7, a point (for example, point A) on the surface of the transmission rod 7 draws an elliptical locus in the vertical direction W and the horizontal direction U. The velocity at the apex of this elliptical trajectory is opposite to the direction of travel of the wave. If the movable body 14 is placed on top of the transmission rod 7 under pressure, the movable body 14 will only touch the transmission rod 7 near the top of the wave.
come into contact with. Therefore, the movable body 14 is driven in the direction opposite to the direction in which the waves travel due to the frictional force between the transmission rod 7 and the movable body 14 and the speed in the lateral direction of the elliptical trajectory.

In addition, 15 in the same figure indicates the horizontal component of the elliptical locus,
A wear-resistant friction material for efficient removal.

Problems to be Solved by the Invention As described above, the conventional ultrasonic linear motor described above excites a vibrating body with a Langevin structure in a longitudinal vibration mode, and transmits the vibration of the imaging surface of the vibrating body to a transmission rod using a horn to transmit bending vibration. Since it is being excited, it is necessary to accurately match the mechanical impedance between the vibrating surface and the horn, and between the horn and the transmission rod. In reality, this is very difficult and results in some losses.

Furthermore, in order to excite only traveling waves in the transmission rod, the vibration energy input from one side must completely disappear from the other side.

In addition, in order to move a relatively small moving body, the vibrating body and transmission rod must be vibrated. Therefore, there were problems of low efficiency and large dimensions.

Means for Solving the Problems A second elastic beam is provided on the free end of a first cantilever beam of an elastic body whose one end is fixed, and a piezoelectric beam is provided on at least one surface of the first beam. By pasting the bodies together and applying an alternating electric field to the piezoelectric body, the first beam is deflected in a plane perpendicular to the plane of the first beam to which the second beam is attached. The second beam is configured to take out the mechanical output from the other end thereof.

Among the vertical and lateral movements of the free end caused by exciting the deflection motion in the first beam whose one end is fixed, the lateral movement is magnified by the second beam provided at the free end of the first beam. , second
By extracting the expanded lateral motion from the tip of the beam, a highly efficient ultrasonic linear motor with a small size can be realized.

EXAMPLE Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an overview diagram illustrating the operation of a moving object according to an embodiment of the present invention. A piezoelectric body 17 is bonded to one surface of the elastic body 16 to form a first cantilever 18. One end of the cantilever 18 is fixed with a fixture 21, and one end of a second beam 19 is fixed to the other end, thereby forming a vibrating body 20. When an AC electric field is applied to the piezoelectric body 17,
The first beam 18 bends and vibrates as shown in the figure.

The tip of the first beam 18 moves as indicated by a trajectory S1.

On the other hand, the second beam 1 provided at the tip of the first beam 18
The tip of 9 moves as shown by the trajectory S2. The effective component of the lateral displacement taken out as mechanical output is the first beam 18
The size has increased from the rest state, and it has been expanded from Xl to X2 in the figure.

FIG. 2 is an overview diagram illustrating the operation of a moving object according to another embodiment of the present invention. A piezoelectric body 23 is bonded to one surface of the elastic body 22 to form a first cantilever beam 24. In addition, a piezoelectric material 26 is bonded to one surface of the elastic material 25, and the first
It constitutes a cantilever beam 27. One end of the cantilever beam 24 is fixed with a fixture 29, and one end of a second beam 27 is fixed to the other end. When an alternating current electric field is applied to the piezoelectric body 23, the first beam 24 bends and moves as shown in the figure. The tip of the first beam 24 moves as indicated by a trajectory S3. On the other hand, when an electric field having the same phase as the above is applied to the piezoelectric body 26 of the second beam 27 provided at the tip of the first beam 24, the tip of the second beam 27 moves as shown by a trajectory S4. The effective component of the lateral displacement taken out as a mechanical output becomes the magnitude of the first beam 24 from its resting state, and is expanded from X3 to X4 in the figure.

FIG. 3 is an overview diagram of an ultrasonic linear motor using the above-described moving body. In the same figure, 30 is the vibrating body 20 or 28 shown in FIGS. 1 and 2. One end of the moving body 30 is fixed by a fixture 31. 32 is a bearing for reducing friction with the rail 34. 33 is a spring for applying pressure between the tip of the moving body 30 and the rail 34.

When an alternating current electric field is applied to the piezoelectric body, the vibrating body 30 causes bending vibration as described above, and is caused to vibrate along the rail 34 due to the lateral displacement component X2 or X4 of the moving body shown in FIG. 1 or 2. and move in the direction of arrow B. The moving speed is a function of the displacement component and the frequency of the driving electric field, and the force at that time is determined by the frictional force between the vibrating body 30 and the rail 34.

Effects of the Invention According to the present invention, the simple structure allows for small size,
A lightweight and highly efficient ultrasonic linear motor can be provided.

[Brief explanation of the drawing]

FIG. 1 is an overview diagram explaining the operation of a vibrating body according to an embodiment of the present invention, FIG. 2 is an overview diagram explaining the operation of a moving body according to another embodiment of the invention, and FIG. An overview diagram of an embodiment of an ultrasonic linear motor using the vibrating body shown in Figure 2 or Figure 2. Figure 4 is an overview diagram of a conventional ultrasonic linear motor. Figure 5 shows the driving principle of an ultrasonic linear motor. It is an explanatory diagram. 416...Elastic body, 17...Piezoelectric body,
18... First beam, 19... Second beam, 20... Vibrating body, 21... Fixture, 22... - Elastic body, 23... Piezoelectric body 24... First beam, 25... Elastic body 26... Piezoelectric body, 27...・Second beam, 28... Vibrating body, 29... Fixture 3
0... Vibrating body, 31... Fixture, 32
...Bearing, 33...Spring 34.
·····rail. Name of agent: Patent attorney Shigetaka Awano and one other person Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A second elastic beam is provided by fixing one end to the free end of the first cantilever beam of the elastic body fixed at one end, and a piezoelectric material is bonded to at least one surface of the first beam. By applying an alternating current electric field to the piezoelectric body, bending vibrations are excited in the first beam in a plane perpendicular to the plane of the first beam to which the second beam is attached, and other beams of the second beam are excited. An ultrasonic linear motor characterized by extracting mechanical output from the tip.