JPH02211072A - Ultrasonic linear motor - Google Patents

Abstract

PURPOSE:To raise the efficiency of an apparatus by supporting a prismatic oscillator at the nodal point of the central part of said oscillator. CONSTITUTION:An oscillator for an ultrasonic linear motor is equipped with an elastic body prism 16 having a square section, piezoelectric ceramics 17a-18b bonded thereto, machine output ends 19a-19b and fixing support holes 20a-20b. Said support holes 20 are provided in the central part of said oscillator and the displacement of a flexural oscillation at that point becomes zero. Therefore, when the position of said oscillator is fixed via said support holes 20, supporting with a small loss made possible.

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 excited by a piezoelectric body.

BACKGROUND OF THE INVENTION In recent years, ultrasonic linear motors have attracted attention in which elastic vibrations are excited in a vibrating body made of a piezoelectric material such as a piezoelectric ceramic, and this vibration 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 disc-shaped piezoelectric bodies 1 and 2 between cylindrical elastic bodies 3 and 4. Piezoelectric body 1
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 vibration surface of the vibrating body 5 is impedance-converted by the horn 6, and matched to the mechanical impedance for the bending vibration 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 motion 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. By sandwiching and fixing the disk-shaped piezoelectric bodies 9 and 10 between cylindrical elastic bodies 11 and 12, a vibrating body 13, which is exactly the same as the vibrating body 5, is constructed. This vibrating body 13 is connected to the horn 8. Therefore, the deflection imaging progressing from one end of the transmission rod toward the other end is transmitted to the vibrating body 13 by the horn 8 and converted into vertical vibration of the imaging 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. By photographing the deflection of the transmission rod 7, the point A on the surface of the transmission rod 7, for example, draws an elliptical locus in the vertical direction W and the horizontal direction U (the speed at the apex of this elliptical trajectory is determined by the wave's progress). If the movable body 14 is installed under pressure on the transmission rod 7, the movable body 14 will move the transmission rod 7 only near the top of the wave.
come into contact with. Therefore, due to the frictional force between the transmission rod 7 and the moving body 14 (!) and the lateral speed of the elliptical trajectory, the moving body 14 is driven in the direction opposite to the direction in which the waves travel.

In addition, 15 in the same figure indicates the horizontal component of the elliptical locus,
Efficient (wear-resistant friction material for 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 converts the longitudinal vibration of the vibrating surface of the vibrating body into bending vibration of a transmission rod using a horn. is converting. Therefore, in order to efficiently excite the traveling wave of bending vibration, it is necessary to accurately match the mechanical impedance between the vibration surface and the horn, and between the horn and the transmission rod. In reality, this is very difficult and results in losses at the contact surface.

In addition, in order to excite only traveling waves in the transmission rod, the vibration energy input from one side must be completely dissipated from the other side. Therefore, part of the imaging energy can be taken out as mechanical output, and most of it is It turns into heat.

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 The present invention provides two adjacent elastic prisms having a square cross section.
A piezoelectric body is pasted on each of the two rectangular surfaces to form a moving body, and the vibrating body is excited with a bending vibration that has a vibration node at the center and is free at both ends. Support and extract mechanical output from both ends.

By supporting the prismatic vibrating body at the center node,
To provide an ultrasonic linear motor with high efficiency and a small shape by making it possible to fix the position of a vibrating body with small loss and extracting mechanical output from both ends of the vibrating body.

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

FIG. 1 shows the structure of a vibrating body according to an embodiment of the present invention.
It is a diagram. In the same figure, work 6 is an elastic prism whose main part has a square cross section, 17a, 17b, 18a, 18b.
are each a piezoelectric ceramic that is polarized in the thickness direction and has electrodes attached to its two main surfaces, and is bonded to the elastic prism 16. In addition, the positive and negative signs in the piezoelectric ceramic are
Indicates the direction of polarization. 19a and 19b are mechanical output ends, and 2°a and 20b are support holes for fixing the vibrating body in position. If an electric field is applied to the piezoelectric ceramics 17a and 17b,
The vibrating body causes bending vibration in a plane perpendicular to the plane of the paper, and when an electric field is applied to the piezoelectric ceramics 18a and 18b, the vibrating body causes bending vibration in a plane parallel to the plane of the paper.

FIG. 2 is a displacement distribution diagram of bending vibration excited in the vibrating body of the present invention shown in FIG. Since the displacement during deflection imaging is 0 at the center of the vibrating body, if the vibrating body is fixed in position through the support hole 20, support with small loss is possible. Also, since the displacement is maximum at both ends of the vibrating body, the speed will be maximized if the mechanical output is extracted from these locations.

The bending vibration excited by the piezoelectric ceramic 17 in FIG. 1 and the bending vibration excited by the piezoelectric ceramic 18 have the same vibration mode and resonance frequency, and their spatial positions are orthogonal. , the phase of the electric field applied to the piezoelectric ceramic 17 and the piezoelectric ceramic 18 is set to 9 in terms of time.
If it is shifted by 0 degrees, both ends of the vibrating body will vibrate in a nearly circular trajectory.

FIG. 3 shows an example of the configuration of an ultrasonic linear motor using the vibrating body as described above. In the figure, 21 is a vibrating body a, 22 is a vibrating body, and a support rod 23 allows
The tips of the two vibrating bodies are connected to each other via support holes so that the rail 26 is sandwiched between them. 24 is a pressure spring, and the pressure adjustment screw 25 allows the tip of the vibrating body to be connected to the rail 2.
Adjust the pressing force with 6.

The amplitudes of vibrations in the direction perpendicular to the rail at the opposing tips of the vibrating body a21 and the vibrating body b22 are made to be in opposite directions, and the amplitudes of vibrations in the direction parallel to the rail are made to be in the same direction. The arrow in the figure is the locus of the tip created by two bending vibrations. As a result, the two sets of opposing tips of the vibrating body a21 and the vibrating body b22 operate alternately so as to move the vibrating bodies themselves along the rails 26.

Effects of the Invention As described above, according to the present invention, an ultrasonic linear motor with a simple structure, small size, light weight, and high efficiency can be provided.

[Brief explanation of the drawing]

1 is a perspective view showing the structure of a vibrating body according to an embodiment of the present invention, FIG. 2 is a displacement distribution diagram of vibration of the vibrating body according to the embodiment of FIG. 1, and FIG. 3 is a diagram of the vibrating body of FIG. 1. FIG. 4 is an overview diagram of a conventional ultrasonic linear motor, and FIG. 5 is an explanatory diagram showing the driving principle of the ultrasonic linear motor. 16...Elastic body, 17a-b...Piezoelectric body, 18a-b...Piezoelectric body, 19a-b...
...Output end, 20a-b...Support hole, 21.
...Camera object a22... Vibrating object b, 23.
...Support rod. Name of agent: Patent attorney Shigetaka Kurino and one other person Figure 1 1 & Piezoelectric material and elastic material No. 2 rl! J V rank distribution chart chart 71 visit

Claims (1)

[Claims] A vibrating body is constructed by pasting piezoelectric bodies on two adjacent rectangular surfaces of an elastic prism having a square cross section,
Exciting flexible vibration in the vibrating body with a vibration node at the center and free bending vibration at both ends, and supporting the vibrating body at the node at the center,
An ultrasonic linear motor characterized in that mechanical output is extracted from both ends.