JPH0937576A - Ultrasonic motor and driving method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic motor the direction of the rotation of which can be bidirectionally changed. SOLUTION: Piezoelectric elements 3a, 3b are secured on a horn 1 and a collar 2 to form the ultrasonic vibrator of an ultrasonic motor. Alternating- current voltage is applied to the piezoelectric elements 3a, 3b to produce longitudinal resonance oscillation in the ultrasonic vibrator, and the rotor 8 of the ultrasonic motor is thereby driven. The ultrasonic vibrator is provided with a step 2a that produces a plurality of longitudinal resonance oscillations to generate bidirectional rotational force so that the rotor 8 can be bidirectionally and rotationally driven.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor for converting ultrasonic vibration energy into rotational energy and a driving method thereof.

[0002]

2. Description of the Related Art An ultrasonic vibrator is constructed by fixing a piezoelectric element to an elastic body, and an AC voltage is applied to the piezoelectric element to generate ultrasonic vibration in the ultrasonic vibrator to rotate a rotor. As such an ultrasonic motor, there is an ultrasonic motor described in the specification of Japanese Patent Application Laid-Open No. 2-55584 filed by the applicant of the present application.

This ultrasonic motor will be described with reference to FIGS. 9 and 10. The ultrasonic transducer 101 in the ultrasonic motor shown in FIGS. 9 and 10 sandwiches a piezoelectric element 102 between a horn 103 having two protrusions each having a gentle slope and a collar 104 and tightening with a bolt 105. It is fixedly configured.

A rotor 106 is supported by a bolt 105 penetrating the shaft hole of the horn 103 via a bearing 107. The rotor 106 has a nut 108 screwed to the bolt 105 and a nut 108. Protrusion 1 of horn 103 via spring 109 mounted between bearing 107 and
The contact surface 111 of 10 is pressed into contact.

When an AC voltage having a predetermined frequency is applied to the electric terminal 112 of the piezoelectric element 102, ultrasonic vibration excited by the strain generated in the piezoelectric element 102 is generated in the horn 103.
9 propagates to the tip of the contact surface 111 to cause vertical vibration to displace the contact surface 111 in the vertical direction in FIG. At the same time, due to the protrusion shape of the horn 103, a part of the vibration changes its direction in the process in which ultrasonic vibration propagates to the contact surface 111 at the tip of the horn 103, and becomes vibration in the direction of arrow 113 shown in FIG. The vibrations in these two directions are combined into vibrations that rotate the rotor 106.

[0006]

However, the above-described ultrasonic motor can only rotate the rotor 106 in one direction determined by the shape of the ultrasonic transducer 101. For this reason, when the rotation direction of the rotor 106 is to be switched and used, it is necessary to mechanically switch the rotation transmission direction using a rotation direction switching mechanism using a gear, a clutch, or the like. There was a problem that it became complicated.

The present invention has been made to solve the above-mentioned problems, and even if the rotation direction is determined to be one direction by the shape of the ultrasonic transducer as in the conventional example,
It is an object of the present invention to provide an ultrasonic motor whose rotation direction can be switched bidirectionally and a driving method thereof.

[0008]

According to the first aspect of the present invention,
An electric-mechanical energy conversion element is fixed to an elastic body to form an ultrasonic vibrator, and by applying an AC voltage to the electric-mechanical energy conversion element, longitudinal resonance vibration is generated in the ultrasonic vibrator and the ultrasonic vibration is generated. An ultrasonic motor for driving a driving body, wherein the ultrasonic transducer is provided with a step for generating a plurality of the longitudinal resonance vibrations and generating a bidirectional rotational force with respect to a driven body. is there.

According to a second aspect of the present invention, the electro-mechanical energy conversion element in the ultrasonic motor according to the first aspect is located at a substantially common node position of the plurality of longitudinal resonance vibrations generated in the ultrasonic vibrator. It is characterized by being arranged.

According to a third aspect of the present invention, there is provided an ultrasonic motor driving method in which an electromechanical energy conversion element is fixed to an elastic body to form an ultrasonic vibrator, and the driven element is joined to the ultrasonic vibrator. With respect to the ultrasonic motor that drives the body, an alternating voltage is applied to the electro-mechanical energy conversion element while changing the frequency, and a plurality of vertical lines are generated in the ultrasonic vibrator based on the steps provided in the ultrasonic vibrator. The rotation direction of the driven body according to the resonance vibration is switched by changing the frequency of the AC voltage.

According to the ultrasonic motor of the first aspect, a step is generated in the ultrasonic vibrator in which a plurality of longitudinal resonance vibrations are generated in accordance with the application of an AC voltage to generate a bidirectional rotational force with respect to the driven body. Since it is provided, the driven body can be rotationally driven in both directions.

According to the ultrasonic motor of the second aspect, the electro-mechanical energy conversion element in the ultrasonic motor of the first aspect is substantially common to the plurality of longitudinal resonance vibrations generated in the ultrasonic oscillator. Since it is arranged at the node position of, a plurality of longitudinal resonance vibrations can be efficiently generated.

According to the ultrasonic motor driving method of the third aspect, by applying an AC voltage to the electro-mechanical energy conversion element while changing the frequency, a step provided on the ultrasonic vibrator is applied. Based on this, it is possible to switch the rotation direction of the driven body according to a plurality of longitudinal resonance vibrations generated in the ultrasonic transducer by changing the frequency of the AC voltage.

[0014]

【Example】

[First Embodiment of the Invention] A first embodiment of the present invention will be described with reference to FIGS.

(Structure) The ultrasonic motor according to the first embodiment of the invention shown in FIGS. 1 and 2 is a horn 1 as an elastic body in which two protrusions 1a having an outer surface having a gentle slope are formed. , The collar 2 as an elastic body having a recessed step 2a at the center of the bottom portion, sandwiches the piezoelectric elements 3a, 3b as electric-mechanical energy conversion elements, and the bolt 7
Then, the ultrasonic transducer is constructed by fastening the space between the bottom surface of the recessed portion 2a of the collar 2 and the root of the protrusion of the horn 1 (portions indicated by the dimensions L4, L5, L3).

A rotor 8 as a driven body is supported by a bolt 7 penetrating the shaft hole of the horn 1 via a bearing 9. The rotor 8 is nut 11a screwed to the bolt 7. The nut 11b and the spring 10 mounted between the nut 11b and the bearing 9 are pressed into contact with the two protrusions of the horn 1.

As shown in FIG. 3, the piezoelectric elements 3a and 3b are polarized in the directions shown by the arrows, and the electrodes 4, 5 and 6 are sandwiched on their respective surfaces, and the electrodes 4 and 6 are placed therebetween. They are connected to form an electric terminal A, and the electrode 5 forms an electric terminal B. Between the electric terminals A and B, a drive power source (not shown) can set the frequency to 100 Vp-p.
An alternating voltage of a certain degree is applied.

In FIG. 1, the total length L1 of the horn 1 and the total length L2 of the collar 2 are substantially equal to each other, or the total length L2 of the collar 2 is about 10% shorter than the total length L1 of the horn 1. Further, the length L3 of the portion of the horn 1 excluding the protrusion 1a and the length L4 of the portion of the collar 2 excluding the recessed portion 2a are substantially equal.

(Operation) The ultrasonic motor of the embodiment of the present invention basically has the same operation principle as that described in the prior art. The amplitude of the drive voltage applied to this ultrasonic motor is constant, and as shown in FIG. 4, the length La of the portion excluding the protrusion 1a of the horn 1 and the length Lb of the horn 1 are constant, and the length Lc of the collar 2 is constant. FIG. 5 and FIG. 6 show the results when an experiment was performed by shaking (changing) and setting so that the rotation output of the ultrasonic motor was maximized only for the frequency of the drive voltage.
In FIGS. 5 and 6, the characteristics marked with X indicate counterclockwise (CCW) characteristics, and the characteristics marked with circles indicate clockwise (CW) characteristics.

As shown in FIG. 5, when Lc is close to the length of La, the ultrasonic motor rotates counterclockwise and Lc
And La are approximately equal, the rotation output becomes maximum.

When Lc is close to Lb, it rotates clockwise, and when Lc is slightly shorter than La, the rotation output becomes maximum. Further, when either Lc is farther from La or Lb, neither clockwise nor counterclockwise rotation occurs.

At this time, it was found that the optimum drive frequency at which the highest rotation output was obtained was different between the clockwise direction and the counterclockwise direction, as shown in FIG.

The results of these experiments are shown in FIG. 4 for the ultrasonic motor of the embodiment of the present invention (La + Lc + L).
When the longitudinal resonance vibration (first mode) of length d) rotates counterclockwise and the piezoelectric elements 3a and 3b are the node positions of the longitudinal resonance vibration of this length, La and Lc are substantially equal to each other. This means that the highest output can be obtained.

Similarly, when the longitudinal resonance vibration of the length (Lb + Lc + Ld) (first-order mode) rotates in the clockwise direction, the piezoelectric elements 3a, 3b reach the nodal position of the vibration of the longitudinal resonance most. This means that high output can be obtained.

Therefore, if these two longitudinal resonance vibrations can be generated without shaking the length of Lc, the piezoelectric element 3
By switching the frequency of the AC voltage applied to a and 3b, the rotor 8 of the ultrasonic motor can be rotated in both the clockwise and counterclockwise directions.

In the embodiment of the present invention, in order to realize the above-described experimental results, as shown in FIGS. 1 and 2, the collar 2 is provided with a recessed step 2a and is shown in FIG.
+ L4 + L5), the first primary longitudinal resonance vibration is generated and the rotor 8 is rotated counterclockwise, as shown in FIG.
The second primary longitudinal resonance vibration is generated with a length of 1 + L2 + L5) to rotate the rotor 8 clockwise. In both cases of the first and second longitudinal resonance vibrations,
The positions where the piezoelectric elements 3a and 3b are arranged are the node positions of the respective longitudinal resonances.

From the above experimental results, by changing the frequency of the AC voltage applied between the electric terminal A and the electric terminal B, the rotor 8 of the ultrasonic motor is rotated clockwise or counterclockwise. It was confirmed to do.

(Effects) According to the embodiment of the present invention, it is possible to realize an ultrasonic motor capable of switching the rotation direction of the rotor 8 between the clockwise direction and the counterclockwise direction by changing the driving frequency of the AC voltage.

[Second Embodiment of the Invention] A second embodiment of the present invention will be described with reference to FIGS.

(Structure) As shown in FIGS. 7 and 8, a horn 21 as an elastic body having two protrusions 21a having a gentle slope on one surface, and an elastic body having a groove-like step 22a in the central portion. The piezoelectric element 23a, 23b as an electro-mechanical energy conversion element is sandwiched between the collar 22 and the collar 22 between the collar 22 and the root of the protrusion of the horn 21 with the bolt 27 (the portions indicated by the dimensions L22, L25, L23). ) Are fastened to form an ultrasonic transducer.

A rotor 28 as a driven body is supported by a bolt 27 penetrating the shaft hole of the horn 21 via a bearing 29. The rotor 28 has a nut 31a screwed to the bolt 27 and The two protrusions 21a of the horn 21 are pressed into contact with each other via a spring 30 mounted between 31b, the nut 31b and the bearing 29.

The piezoelectric elements 23a and 23b are constructed similarly to those shown in FIG. 3 of the first embodiment of the invention,
It has an electric terminal A and an electric terminal B. Further, as in the case of the first embodiment of the invention, the total length L of the horn 21 is L.
21 and the overall length L22 of the collar are approximately equal, or L22 is shorter by about 10%, and the length L23 of the portion excluding the protrusion 21a of the horn 21 and the length L to the step 22a of the collar 22.
24 is configured approximately the same.

(Operation) In the embodiment of the present invention, in order to realize two longitudinal resonance vibrations respectively corresponding to the clockwise and counterclockwise directions of rotation described in the first embodiment of the invention. The collar 22 is provided with a groove-like step 22a.

As a result, the first primary longitudinal resonance vibration is generated with the length of (L23 + L24 + L25) to rotate the rotor 28 counterclockwise, and the second with the length of (L21 + L22 + L25).
The primary longitudinal resonance vibration is generated to rotate the rotor 28 in the clockwise direction.

In any of these cases, the piezoelectric element 23
This means that a and 23b are arranged at the node positions of the respective longitudinal resonance vibrations.

Then, when the frequency of the AC voltage applied between the electric terminal A and the electric terminal B is changed, the rotor 28 is rotated clockwise or counterclockwise as in the first embodiment of the invention. It was confirmed.

(Effect) Also in the embodiment of the present invention,
It is possible to realize an ultrasonic motor in which the rotation direction of the rotor 28 is switched by changing the drive frequency of the AC voltage.

[0038]

According to the first aspect of the invention, it is possible to provide an ultrasonic motor capable of bidirectionally rotating and driving a driven body.

According to the second aspect of the present invention, it is possible to provide an ultrasonic motor capable of efficiently generating a plurality of longitudinal resonance vibrations and efficiently rotationally driving a driven body in both directions. .

According to the third aspect of the invention, it is possible to provide an ultrasonic motor capable of switching the bidirectional rotation direction of the driven body by changing the frequency of the AC voltage.

[Brief description of drawings]

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

FIG. 2 is a partially cutaway sectional view showing an ultrasonic motor according to a first embodiment of the invention.

FIG. 3 is an explanatory view showing an enlarged piezoelectric element in the ultrasonic motor according to the first embodiment of the invention.

FIG. 4 is an explanatory diagram showing a dimensional relationship for explaining a driving principle of the ultrasonic motor according to the first embodiment of the invention.

5 is a characteristic diagram showing clockwise / counterclockwise rotation output when the size of the collar of the ultrasonic motor having the size relationship shown in FIG. 4 is changed.

6 is a characteristic diagram showing an optimum drive frequency when the size of the collar of the ultrasonic motor having the size relationship shown in FIG. 4 is changed.

FIG. 7 is a front view showing an ultrasonic motor according to a second embodiment of the invention.

FIG. 8 is a partially cutaway sectional view showing an ultrasonic motor according to a second embodiment of the invention.

FIG. 9 is a front view showing a conventional ultrasonic motor.

FIG. 10 is a partially cutaway sectional view showing a conventional ultrasonic motor.

[Explanation of symbols]

 1 Horn 1a Protrusion 2 Collar 2a Step 3a Piezoelectric Element 3b Piezoelectric Element 7 Bolt 8 Rotor 9 Bearing 10 Spring 11a Nut 11b Nut 21 Horn 21a Protrusion 22 Collar 22a Step 23a Piezoelectric Element 23b Piezoelectric Element 27 Bolt 28 Rotor Spring 29a Nut 30 Bearing 31b nut

Claims (3)

[Claims] 1. An ultrasonic transducer is formed by fixing an electro-mechanical energy conversion element to an elastic body, and a longitudinal resonance vibration is applied to the ultrasonic transducer by applying an AC voltage to the electro-mechanical energy conversion element. And a step for generating a plurality of the longitudinal resonance vibrations to generate a bidirectional rotational force with respect to the driven body. Characteristic ultrasonic motor. 2. The ultrasonic motor according to claim 1, wherein the electro-mechanical energy conversion element is arranged at a substantially common node position of the plurality of longitudinal resonance vibrations generated in the ultrasonic vibrator. . 3. An electric-mechanical energy conversion element is fixed to an elastic body to form an ultrasonic vibrator, and the electric motor is driven by an ultrasonic motor that drives a driven body bonded to the ultrasonic vibrator. An alternating voltage is applied to the mechanical energy conversion element while changing the frequency, and the rotational direction of the driven body is changed in accordance with a plurality of longitudinal resonance vibrations generated in the ultrasonic vibrator based on the steps provided in the ultrasonic vibrator. A method for driving an ultrasonic motor, characterized in that switching is performed according to a change in voltage frequency.