Driver of vibrator, method of driving the same, lens driver, vibration device, and imaging device

Patent metadata

Field	Value
Publication number	US-9823543-B2
Application number	US-201414574296-A
Country	US
Kind code	B2
Filing date	Dec 17, 2014
Priority date	Dec 20, 2013
Publication date	Nov 21, 2017
Grant date	Nov 21, 2017

Abstract

One aspect of the present invention relates to a driver of a vibrator including: a control section; and an alternating current signal generation section configured to generate an alternating current signal based on an output from the control section, and to apply the alternating current signal to the vibrator, wherein the control section is configured to lower a frequency of the alternating current signal, and to change, after the frequency change, at least one of a voltage ratio and a phase difference of the alternating current signal such that the ellipse ratio of the elliptical motion changes from a first ellipse ratio to a second ellipse ratio, the second ellipse ratio has a larger ratio of a component in a moving direction in the elliptical motion to a component in a direction perpendicular to the moving direction in the elliptical motion than the first ellipse ratio.

First claim

What is claimed is:

1. A driver of a vibrator comprising:
a control section; and
an alternating current signal generation section configured to generate alternating current signals based on an output from the control section, and to apply the alternating current signals to the vibrator, wherein,
the control section is configured:
to perform first setting of setting a frequency of the alternating current signals applied to the vibrator to a first frequency, and setting at least one of a voltage ratio and a phase difference of the alternating current signals applied to the vibrator such that an ellipse ratio of elliptical motion caused in a contact portion of the vibrator becomes a first ellipse ratio;
to perform, after the first setting, second setting of setting the frequency to a second frequency, and setting at least one of the voltage ratio and the phase difference such that the ellipse ratio becomes the first ellipse ratio; and
to perform, after the second setting, third setting of setting the frequency of the alternating current signals applied to the vibrator to the second frequency, and setting at least one of the voltage ratio and the phase difference such that the ellipse ratio becomes a second ellipse ratio, wherein:
the vibrator and a driven body contacting the contact portion perform relative movement in a moving direction by the elliptical motion,
the second frequency is smaller than the first frequency, and
the second ellipse ratio has a larger ratio of a component in the moving direction in the elliptical motion to a component in a direction perpendicular to the moving direction in the elliptical motion than the first ellipse ratio.

2. The driver according to claim 1 , wherein the control section is configured to compare the second frequency and a predetermined frequency when the vibrator has not been driven after performing the second setting, and to set the frequency of the alternating current signals applied to the vibrator to the first frequency and to set at least one of the voltage ratio and the phase difference of the alternating current signals applied to the vibrator such that the ellipse ratio of the elliptical motion caused in the contact portion of the vibrator becomes the first ellipse ratio when the second frequency is smaller than the predetermined frequency.

3. A vibration device, comprising:
a vibrator including an elastic member and an electro-mechanical transducer fixed to the elastic member; and
the driver according to claim 1 .

4. The vibration device according to claim 3 , wherein the control section is configured to compare the frequency and a predetermined frequency when the vibrator has not been driven after performing the second setting, and to set the frequency of the alternating current signals applied to the vibrator to the first frequency and to set at least one of the voltage ratio and the phase difference of the alternating current signals applied to the vibrator such that the ellipse ratio of the elliptical motion caused in the contact portion of the vibrator becomes the first ellipse ratio when the second frequency is smaller than the predetermined frequency.

5. The vibration device according to claim 3 ,
wherein the electro-mechanical transducer includes two electrodes,
wherein a first vibration mode is caused in the vibrator when alternating current voltages having a same phase are applied to the two electrodes,
wherein a second vibration mode is caused in the vibrator when alternating current voltages having reversed phases are applied to the two electrodes, and
wherein the elliptical motion is caused by combining the first vibration mode and the second vibration mode.

6. The vibration device according to claim 5 ,
wherein the ellipse ratio of the elliptical motion caused in the contact portion of the vibrator is changed by adjustment of a phase difference of the alternating current voltages applied to the two electrodes.

7. The vibration device according to claim 3 ,
wherein the electro-mechanical transducer includes one or more first electrodes provided to generate a first vibration mode in the vibrator, and one or more second electrodes provided to generate a second vibration mode, and
wherein the elliptical motion is caused by applying alternating current voltages to the one or more first electrodes and the one or more second electrodes.

8. The vibration device according to claim 7 , wherein the ellipse ratio of the elliptical motion caused in the contact portion of the vibrator is changed by adjustment of a voltage ratio of the alternating current voltages applied to the electrodes.

9. An imaging device comprising:
a lens;
a lens holder that holds the lens;
the vibration device according to claim 3 configured to drive the lens holder; and
an image pickup element on an optical axis of the lens.

10. The driver according to claim 1 , wherein the control section performs the first setting and the second setting before the relative movement starts and performs the third setting after the relative movement starts.

11. A method of driving a vibrator, comprising successively, the steps of:
first, setting a frequency of alternating current signals applied to the vibrator to a first frequency, and setting at least one of a voltage ratio and a phase difference of the alternating current signals such that an ellipse ratio of elliptical motion caused in a contact portion of the vibrator becomes a first ellipse ratio,
second, setting the frequency to a second frequency, and setting at least one of the voltage ratio and the phase difference such that the ellipse ratio becomes the first ellipse ratio, and
third, setting the frequency of the alternating current signals applied to the vibrator to the second frequency, and setting at least one of the voltage ratio and the phase difference such that the ellipse ratio becomes a second ellipse ratio, wherein:
the vibrator and a driven body contacting the contact portion perform relative movement in a moving direction by the elliptical motion,
the second frequency is smaller than the first frequency, and
the second ellipse ratio has a larger ratio of a component in the moving direction in the elliptical motion to a component in a direction perpendicular to the moving direction in the elliptical motion than the first ellipse ratio.

12. The method for driving a vibrator according to claim 11 , wherein a drive frequency applied when the vibrator is started is higher than a frequency started to work when the vibrator has been started with the first ellipse ratio.

13. The method for driving a vibrator according to claim 11 , wherein, when the driven body is not relatively moved with respect to the vibrator until the frequency becomes a predetermined frequency when the frequency is swept at the first ellipse ratio, the frequency is caused to be in a higher state again, and is then swept in a direction into which the frequency becomes lowered.

14. The method for driving a vibrator according to claim 11 , wherein the ellipse ratio of the elliptical motion caused in the contact portion of the vibrator is changed by adjustment of a phase difference of alternating current voltages applied to two electrodes of the vibrator.

15. A driver of a vibrator including a contact portion that performs elliptical motion, the driver comprising:
a generation section configured to generate alternating current signals to be applied to the vibrator; and
a setting section configured to set a frequency of the alternating current signals and at least one of a voltage ratio and a phase difference of the alternating current signal

Assignees

• Canon Kk

Inventors

• Atsuta Akio

Classifications

• H02N2/001

  Driving devices, e.g. vibrators · CPC title

• G02B7/08

  adapted to co-operate with a remote control mechanism · CPC title

• H02N2/025

  Inertial sliding motors · CPC title

• H01L41/042

  Electricity · mapped topic

• G02B7/09

  adapted for automatic focusing or varying magnification · CPC title