JPH09117166A - Ultrasonic motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To freely set a drive thrust to be generated while optimally maintaining traveling characteristics when slightly moving by forming a piezoelectric body with a plurality of systems, constituting each system with a plurality of piezoelectric element groups, and at the same time using at least the same number of sliding members as the number of piezoelectric element groups for constituting each system. SOLUTION: Sliding members 31 and 32 are provided on the bottom surface of an elastic body 1, two lamination-type piezoelectric bodies 21 and 22 for constituting a first system and two lamination-type piezoelectric bodies 23 and 24 for constituting a second system are provided in parallel on the bottom surface of the elastic body 1, and a pin 4 is planted and fixed at the center of the side surface of the elastic body 1, thus supporting the pin 4 so that it can freely rotate for the support body. Then, two burst waves whose phases are shifted by 90 degrees are applied to the first and second systems and two vibrations of vertical and flex vibrations are generated at the elastic body 1 for performing the elliptical motion of the two sliding members 31 and 32 and linearly moving a body to be driven, thus selecting the optimum characteristic of fine amount of travel and an arbitrary drive thrust.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor using an electromechanical energy conversion element such as a piezoelectric element as a driving source.

[0002]

2. Description of the Related Art In recent years, ultrasonic (linear) motors have been attracting attention because they have a smaller outer size than electromagnetic type motors and can provide a strong driving thrust. As an example of a conventional ultrasonic motor, there is one described in the specification (Japanese Patent Application No. 4-321096) filed previously by the present applicant, which will be described below with reference to FIGS. 4 to 7. .

FIG. 4 is a diagram for explaining the principle of an ultrasonic linear motor which uses a piezoelectric element as a drive source and is capable of translational movement. That is, the ultrasonic transducer is composed of an elastic body 1, a laminated piezoelectric body (piezoelectric element group) 2 and a sliding member 3, and two laminated bodies are formed on the upper end surface of the rectangular parallelepiped elastic body 1 in the longitudinal direction. The piezoelectric body 2 is sandwiched, and a plurality of sliding members 3 are fixed to the lower end surface of the elastic body 1 which is an antinode of vibration.

In the ultrasonic vibrator having such a structure,
When a sinusoidal voltage is applied to the laminated piezoelectric body 2, the elastic body 1 receives two kinds of vibrations as shown in FIG.
As shown in FIG. 5A, a simple elastic movement along the longitudinal direction of the elastic body 1 and a transverse standing wave as a secondary standing wave propagating in the longitudinal direction as shown in FIG. Vibration) and excited at the same time.

The length and width of the elastic body 1 are set so that the primary resonance frequency of the stretching motion and the frequency of the secondary standing wave of the transverse wave match. In the ultrasonic transducer of FIG. 4,
At the antinode position of the vibration of the standing wave, the displacements of the two types of vibrations are combined, and the mass point of the elastic body 1 vibrates along an elliptical locus. Therefore, when the sliding member 3 is disposed at the antinode of the vibration and the driven body 8 is pressed against the sliding member 3 as shown in FIG. 7, the driven body 8 causes the elliptical vibration as described above. Moves in translation under the action of.

FIG. 6 shows the entire structure of an actual ultrasonic linear motor equipped with the ultrasonic vibrator described above. However, the difference from FIG. 4 is that the sliding member 3 is made of the elastic body 1. It is a point fixed to both ends of the lower end surface.

The elastic body 1 is supported by the locking member 4 at a position that serves as a node of the secondary standing wave, and the locking member 4 is pressed by the pressing force adjusting screw 6 supported by the frame body 5. The ultrasonic transducer is pressed against the driven body 8 by being biased by the adjustable coil spring 7. A linear guide 9 is provided at the lower end of the linear guide 9 and is held so as to be linearly movable in the left-right direction while engaging with the guide rail 8a and receiving the pressing force.

When a burst wave (continuous wave cut in a certain range) is applied to the laminated piezoelectric body 2 of the ultrasonic motor having such a structure, the ultrasonic motor moves a minute amount.
The relationship between the minute movement amount and the pressing force per unit area in this case is as shown in FIG. As is clear from FIG.
By changing the pressing force per unit area of the portion of the driven body 8 where the driven body 8 and the sliding member 3 are in contact with each other, the movement amount shown by the broken line and the driving thrust shown by the solid line also change.

[0009]

The conventional ultrasonic motor described above has the following problems. To increase the driving thrust obtained by the ultrasonic vibrator without changing the size of the ultrasonic vibrator described above, it is possible to increase the pressing force to the point B side of FIG. 7 as shown in FIG. However, in this case, the minute movement characteristic may not be the optimum characteristic.

On the other hand, when the minute movement characteristic is the optimum characteristic (point A in FIG. 7), the driving thrust is uniquely determined, and the required driving thrust may not be obtained. From this, a method of changing the size of the ultrasonic transducer can be considered as a configuration of the ultrasonic motor that simultaneously satisfies the drive thrust and the minute movement amount, but even in this case, it can be seen from the configuration shown in FIG. In addition, the shape of the ultrasonic transducer cannot be arbitrarily determined because it is limited by the outer dimensions of the piezoelectric body 2.

If the height and width of the sheet of FIG. 4 are changed by the method of changing the size of the ultrasonic vibrator, the vibration frequency of the ultrasonic vibrator will change. For this reason, it is desirable to change the thickness of the ultrasonic transducer in the direction normal to the paper surface of FIG.

However, when the thickness of the ultrasonic transducer is changed, it is difficult to obtain a piezoelectric body having an appropriate size, and it is expensive to order a special piezoelectric body. There is a problem.

The present invention has been made in order to eliminate the above-mentioned conventional problems, and when a minute movement is performed, the driving thrust generated while keeping its movement characteristics optimal can be freely set, which is simple. An object is to provide an inexpensive ultrasonic motor having a configuration.

[0014]

In order to achieve the above object, the invention according to claim 1 provides a plurality of sliding members at predetermined positions on the bottom surface side of an elastic body having a rectangular parallelepiped shape, By disposing a piezoelectric body on the surface side of the elastic body facing the position where the sliding member is disposed, and applying a sinusoidal voltage to the piezoelectric body, the piezoelectric body is moved in the longitudinal direction of the elastic body. In an ultrasonic motor for generating an elliptic vibration by synthesizing a stretching vibration along with a bending vibration propagating in the longitudinal direction of the elastic body, the piezoelectric body has a plurality of systems, and each system includes a plurality of piezoelectric element groups. However, the number of the sliding members is at least the same as that of the piezoelectric element group, which is an ultrasonic motor.

According to the invention corresponding to claim 1, the piezoelectric members are provided in a plurality of systems, and the number of the sliding members is at least the same as the number of piezoelectric element groups constituting each system. The contact area with and becomes large, and a high driving thrust can be obtained by the pressing force per unit area. Therefore, when a minute movement is performed, the drive thrust generated while keeping the movement characteristics optimal can be freely set, and the cost is simple and the cost is low.

In order to achieve the above object, the invention according to claim 2 is characterized in that the piezoelectric element groups for each system are arranged in parallel in the thickness direction or the height direction of the elastic body. It is the ultrasonic motor according to 1.

According to the invention corresponding to claim 2, in addition to the effect of claim 1, it is suitable for use in an elastic body having a margin in the dimension corresponding to the thickness direction. In order to achieve the above object, the invention according to claim 3 is such that the piezoelectric element groups of each system are linear in the longitudinal direction of the elastic body, and the piezoelectric element groups of different systems are staggered. The ultrasonic motor according to claim 1, wherein the ultrasonic motor is arranged. According to the invention corresponding to claim 3, in addition to the effect of claim 1, it is suitable for use in an elastic body having a margin in a dimension corresponding to the longitudinal direction.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment> FIG. 1 shows the essential parts of the first embodiment.
That is, it is a perspective view showing only an ultrasonic transducer, in which a laminated piezoelectric body (piezoelectric element group) 21, 2 is attached to a rectangular parallelepiped elastic body 1.
2, 23, 24, sliding members 31, 32 (only two are shown in the figure, but actually four) and a pin 4
Are provided as follows. That is, the sliding members 31 and 32 are arranged on the bottom surface of the elastic body 1 at positions where the elastic body 1 is antinode when the elastic body 1 is flexurally vibrated. In the thickness direction orthogonal to the longitudinal direction (vibration direction) of 1, the two laminated piezoelectric bodies 21 and 22 forming the first system are arranged side by side, and the longitudinal direction of the elastic body 1 is the piezoelectric body. Two laminated piezoelectric bodies 23 and 24 forming a second system are arranged in parallel in the thickness direction at positions close to the bodies 21 and 22. A pin 4 is provided at the center of the side surface of the elastic body 1 (the surface orthogonal to the top and bottom surfaces)
Is fixed by being planted, and the pin 4 is rotatably supported with respect to a holding body (not shown). Then, the ultrasonic transducer as described above is pressed by a pressing mechanism (not shown), and the sliding member 3
The reference numerals 1 and 32 are configured to come into contact with a driven body (not shown) disposed below this.

The elastic body 1 is different in that the dimension in the thickness direction is twice as thick as the conventional one. In the first embodiment configured as described above, a first system including a set of laminated piezoelectric bodies 21 and 22 and a second system including a set of laminated piezoelectric bodies 23 and 24 are provided.
Two burst waves whose phases are shifted by 90 degrees are applied. In this case, in each system, in-phase burst waves are generated.

As a result, as shown in FIG. 5, two vibrations, that is, a longitudinal vibration and a bending vibration are generated in the elastic body, and the two sliding members vibrate in an elliptical manner, so that the driven body moves linearly. At this time, the amount of movement in a single burst wave is determined by the pressing force per unit area between the driven body and the sliding member, as shown in FIG. However, it goes without saying that the amount of movement depends on the inertial load of the driven body and the rolling load of the linear guide (not shown).

From the above, the thickness of the elastic body in the thickness direction is increased, and the first system and the second system which are composed of the piezoelectric bodies 21 and 22 are used.
By configuring the second system composed of 3, 24, it is possible to select the optimum characteristic of the minute movement amount and an arbitrary driving thrust, and the applied voltage to the piezoelectric body can be lowered.

Assuming that the conventional technique is used and the elastic body dimension is unnecessarily increased from the dimension of the laminated piezoelectric body,
The elastic body is required to have a small flexibility (high rigidity) and a large expansion and contraction force obtained by the piezoelectric body. Therefore, it is necessary to apply a high voltage to the piezoelectric body. The body may be destroyed, and the vibration of the elastic body may become unstable.

According to the first embodiment, the piezoelectric bodies 21-
A stable vibration can be generated in the elastic body by simply applying a sinusoidal low voltage to 24, and further, when assembled as a motor, the optimum minute movement characteristics are maintained and a high driving thrust is generated. You can Further, since the conventional drive circuit can be used, the cost is lower than that in the case of using a special drive circuit, and the simple configuration is sufficient. Further, the elastic body 1 is suitable for being used for those having a margin in the dimension corresponding to the thickness direction.

<Second Embodiment> FIG. 2 is a perspective view showing only the ultrasonic transducer of the second embodiment. The difference from the embodiment of FIG. 1 is that the thickness of the elastic body 1 is different. The thickness is thin and is half of that in FIG. 1. Piezoelectric bodies 21 to 24 are arranged in a straight line on this upper surface, and piezoelectric bodies 21 and 22 constituting the first system,
The piezoelectric bodies 23 and 24 forming the second system are arranged alternately. On the bottom surface of the elastic body 1, four sliding members 31 to
34 are arranged at predetermined positions with a space therebetween. In this case, the arrangement positions of the sliding members 31 to 34 are positions where the elastic body 1 is the antinode of bending vibration. Other configurations are
This is the same as the first embodiment.

In the second embodiment configured as described above, a first system including a set of laminated piezoelectric bodies 21 and 22 and a second system including a set of laminated piezoelectric bodies 23 and 24 are provided. Two burst waves whose phases are shifted by 90 degrees are applied.

As a result, as shown in FIG. 5, stretching vibration and bending vibration in the longitudinal direction are simultaneously excited in the elastic body 1. As a combination of these two vibrations, four sliding members 31, 32,
33 and 34 will be elliptically vibrated.

Here, the set of the sliding members 31, 32 and the set of 33, 34 provided at the antinode of the bending vibration vibrate with a phase difference of 180 degrees. As a result, the driven body that comes into contact with the four sliding members 31 to 34 (not shown) moves linearly.

According to the second embodiment described above, the sliding members 31 to 3 are even under the optimum pressing force of the minute movement characteristic.
Since the contact area between 4 and the driven body is increased, a large driving thrust is generated. However, it goes without saying that the amount of movement depends on the inertial load of the driven body and the rolling load of the linear guide (not shown).

From the above, the length of the elastic body 1 in the longitudinal direction is increased, the piezoelectric bodies 21 to 24 are arranged in a straight line, and the sliding members 31 to 34 are arranged at the antinodes of bending vibration. As a result, it is possible to maintain the optimum micromovement characteristics as a motor and generate a high driving thrust. Further, it is suitable for use in the elastic body 1 having a sufficient dimension corresponding to the longitudinal direction.

<Modification> In the embodiment of FIG. 1, the piezoelectric bodies 21, 22, 23, 24 are arranged in the thickness direction of the upper surface of the elastic body 1.
Although they are arranged side by side, they may be vertically stacked on the upper surface side of the elastic body 1 as shown in FIG.

Further, in the above-mentioned embodiment, an example in which the first and second systems are constituted by four laminated piezoelectric materials has been given. However, in addition to this, if the number is an even number such as six or eight, then how many But it's okay.

Further, in the above-described embodiment, the case where the number of the laminated piezoelectric bodies (21 to 24) and the number of the sliding members (31 to 34) are the same has been described. The number of sliding members may be greater than the number of piezoelectric bodies.

[0033]

As described above, according to the present invention, it is possible to provide an inexpensive ultrasonic motor with a simple structure, in which the driving thrust generated while maintaining the optimum movement characteristics can be set freely during a minute movement. .

[Brief description of the drawings]

FIG. 1 is a perspective view showing an ultrasonic transducer according to a first embodiment of an ultrasonic motor of the present invention.

FIG. 2 is a perspective view showing an ultrasonic oscillator according to a second embodiment of the ultrasonic motor of the present invention.

FIG. 3 is a perspective view showing a modified example of the ultrasonic transducer of FIG.

FIG. 4 is a front view showing an ultrasonic transducer as an example of a conventional ultrasonic motor.

5 is an operation explanatory view of the ultrasonic transducer of FIG.

6 is a front view showing the overall configuration of a conventional ultrasonic motor using the ultrasonic vibrator of FIG.

FIG. 7 is a diagram showing a relationship between a minute movement amount and a driving thrust force and a pressing force per unit area for explaining problems of the ultrasonic motor of FIG.

[Explanation of symbols]

1 ... Elastic body, 2, 21, 22, 23, 24 ... Laminated piezoelectric body (piezoelectric element group), 3, 31, 32, 33, 34 ... Sliding member, 4 ... Pin, 8 ... Driven body.

Claims (3)

[Claims] 1. A plurality of sliding members are respectively arranged at predetermined positions on the bottom surface side of an elastic body having a rectangular parallelepiped shape, and are opposed to the positions of the elastic body where the sliding members are arranged. By disposing a piezoelectric body on the surface side and applying a sinusoidal voltage to the piezoelectric body, the stretching vibration along the longitudinal direction of the elastic body and the bending vibration propagating in the longitudinal direction of the elastic body are respectively synthesized. In the ultrasonic motor that generates elliptical vibration, the piezoelectric body is composed of a plurality of systems, each system is composed of a plurality of piezoelectric element groups, and the sliding member is at least the same number as the piezoelectric element group. And ultrasonic motor. 2. The ultrasonic motor according to claim 1, wherein the piezoelectric element groups for each system are arranged side by side in a thickness direction or a height direction of the elastic body. 3. The piezoelectric element group of each system is arranged in a straight line in the longitudinal direction of the elastic body, and the piezoelectric element groups of different systems are arranged alternately. Ultrasonic motor.