METHOD OF DRIVING VIBRATION ACTUATOR, DRIVE DEVICE, AND IMAGE PICKUP APPARATUS

• US 20170279380A1
• Filed: 10/06/2015
• Published: 09/28/2017
• Est. Priority Date: 10/10/2014
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: ATSUTA, Akio
• Granted Patent: US 10,742,139 B2
• Time in Patent Office: Days
• CPC Class Codes: B23Q 1/34 Relative movement obtained by use of deformable elements, e.g. piezoelectric, magnetostrictive, elastic or thermally-dilatable elements sensitive elements capable of producing movement or displacement for purposes not limited to measurement G12B1/00
• CPC Class Codes: B23Q 5/50 feeding step-by-step
• CPC Class Codes: G02B 7/04 with mechanism for focusing or varying magnification
• CPC Class Codes: G02B 7/08 adapted to co-operate with a remote control mechanism
• CPC Class Codes: H02N 2/001 Driving devices, e.g. vibrators
• CPC Class Codes: H02N 2/142 Small signal circuits; Means for controlling position or derived quantities, e.g. speed, torque, starting, stopping, reversing
• CPC Class Codes: H02N 2/163 Motors with ring stator

Abstract

A drive device for a vibration actuator, which makes it possible to perform low-speed and stable driving and expand a dynamic range of driving speed. A first switching circuit and a second switching circuit apply a first drive signal and a second drive signal for exciting vibration, to an electromechanical energy conversion element of a vibrating body. A position detection sensor acquires information on a relative position between the vibrating body and a driven body in pressure contact with each other. An MPU switches the first and second drive signal to a third drive signal and a fourth drive signal, respectively, based on the acquired information, to thereby change a position at which a largest one of peaks of amplitude of vibration excited in the vibrating body is formed.

Claims

1. A drive device for a vibration actuator that includes a vibrating body and a driven body in pressure contact with each other, and causes relative movement between the vibrating body and the driven body by vibration excited in the vibrating body, comprising:

a drive unit configured to apply a first drive signal and a second drive signal for exciting vibration, to an electromechanical energy conversion element of the vibrating body;

an acquisition unit configured to acquire information on a relative position between the vibrating body and the driven body; and

a control unit configured to switch the first drive signal and the second drive signal applied from said drive unit to the electromechanical energy conversion element, to a third drive signal and a fourth drive signal, respectively, based on the information acquired by said acquisition unit, to thereby change a position at which a largest one of peaks of amplitude of vibration excited in the vibrating body is formed.

2. The drive device according to claim 1, wherein switching of the first drive signal and the second drive signal to the third drive signal and the fourth drive signal is performed by switching a phase difference between the first drive signal and the second drive signal.

3. The drive device according to claim 1, wherein switching of the first drive signal and the second drive signal to the third drive signal and the fourth drive signal is performed by fixing one of the first drive signal and the second drive signal, and changing the other drive signal.

4. The drive device according to claim 1, wherein said acquisition unit sets a predetermined number of pulses for a predetermined amount of movement of the driven body with respect to the vibrating body, and acquires the relative position between the vibrating body and the driven body as a value of the number of pulses.

5. The drive device according to claim 1, wherein both the vibrating body and the driven body have an annular shape and are arranged coaxially with each other,

wherein the first drive signal and the second drive signal are applied to the electromechanical energy conversion element with a predetermined phase difference, whereby progressive vibration is excited in the vibrating body,

wherein the driven body has convex portions protruding toward the vibrating body on a sliding surface that slides on the vibrating body, and

wherein said control unit switches the first drive signal and the second drive signal to the third drive signal and the fourth drive signal, respectively, according to the relative movement between the vibrating body and the driven body, such that the convex portions of the driven body are brought into contact with the vibrating body at positions in a circumferential direction of the vibrating body at which the largest one of the peaks of the amplitude of the progressive vibration generated is formed, to thereby switch the position in the circumferential direction of the vibrating body at which the largest one of the peaks of the amplitude of the progressive vibration is formed.

6. The drive device according to claim 5, wherein the number of times of operation for switching the position in the circumferential direction of the vibrating body at which the largest one of the peaks of the amplitude of the progressive vibration is formed is at least t×

m×

2, assuming that the number of the convex portions of the driven body is represented by t, and the number of waves of vibration formed per circumference of the vibrating body, which is calculated from an electrode pattern of the electromechanical energy conversion element, is represented by m.

7. The drive device according to claim 1, wherein said control unit stores a position at which a speed of the driven body with respect to the vibrating body becomes minimum or maximum when the electromechanical energy conversion element is driven in a state in which frequency of the first and second drive signal is not changed, and determines, with reference to the stored position, a position at which a largest one of peaks of amplitude of the progressive vibration generated in the vibrating body is formed.

8. The drive device according to claim 1, wherein the vibrating body includes a vibration detection unit configured to detect vibration generated in the vibrating body,

wherein said control unit stores a position at which a phase difference between a signal from said vibration detection unit and the first drive signal or the second drive signal becomes minimum or maximum when the electromechanical energy conversion element is driven in a state in which frequency of the first and second drive signals is not changed, and determines, with reference to the stored position, a position at which a largest one of peaks of amplitude of the progressive vibration generated in the vibrating body is formed.

13. A vibration type driving apparatus comprising:

a vibrating body;

a driven body in pressure contact with the vibrating body; and

the drive device according to claim 1.

9. An image pickup apparatus comprising:

a lens;

a vibration actuator that moves said lens in an optical axis direction;

an image pickup element that picks up an optical image formed by said lens; and

a drive device that drives said vibration actuator,

said vibration actuator including;

a vibrating body formed by attaching an electromechanical energy conversion element to an elastic body, and

a driven body in pressure contact with the vibrating body,

wherein relative movement between the vibrating body and the driven body is caused by vibration excited in the vibrating body,

said drive device including;

a drive unit configured to apply a first drive signal and a second drive signal for exciting vibration, to the electromechanical energy conversion element of the vibrating body,

an acquisition unit configured to acquire information on a relative position between the driven body and the vibrating body, and

a control unit configured to switch the first drive signal and the second drive signal applied from said drive unit to the electromechanical energy conversion element, to a third drive signal and a fourth drive signal, respectively, based on the information acquired by said acquisition unit, to thereby change a position at which a largest one of peaks of amplitude of vibration excited in the vibrating body is formed.

10. A method of controlling a drive device for driving a vibration actuator that includes a vibrating body and a driven body in pressure contact with each other, and causes relative movement between the vibrating body and the driven body by vibration excited in the vibrating body, the method comprising:

applying a first drive signal and a second drive signal for exciting vibration, to an electromechanical energy conversion element of the vibrating body;

acquiring information on a relative position between the vibrating body and the driven body; and

switching the first drive signal and the second drive signal applied to the electromechanical energy conversion element, to a third drive signal and a fourth drive signal, respectively, based on the information acquired by said acquiring, to thereby change a position at which a largest one of peaks of amplitude of vibration excited in the vibrating body is formed.

11. A method of driving a vibration actuator including a vibrating body formed by attaching an electromechanical energy conversion element to an elastic body, and a driven body in pressure contact with the vibrating body, relative movement between the vibrating body and the driven body being caused by vibration excited in the vibrating body, the method comprising:

applying a first drive signal and a second drive signal having a predetermined frequency to the electromechanical energy conversion element with a fixed phase difference, thereby exciting progressive vibration in the vibrating body;

acquiring a speed profile indicative of a relationship between a position and a speed of the driven body with respect to the vibrating body in a case where the relative movement between the driven body and the vibrating body is caused by the vibration excited in the vibrating body;

detecting a lowest-speed position at which the speed of the driven body with respect to the vibrating body becomes lowest, from the speed profile acquired by said acquiring; and

acquiring information on a relative position between the driven body and the vibrating body, and switching the first drive signal and the second drive signal applied to the electromechanical energy conversion element to a third drive signal and a fourth drive signal, respectively, based on the information on the relative position and the lowest-speed position, thereby changing a position at which a largest one of peaks of amplitude of the progressive vibration excited in the vibrating body is formed.

12. A method of driving a vibration actuator including a vibrating body formed by attaching an electromechanical energy conversion element to an elastic body, and a driven body in pressure contact with the vibrating body, relative movement between the vibrating body and the driven body being caused by vibration excited in the vibrating body, the method comprising:

applying a first drive signal and a second drive signal having a predetermined frequency to the electromechanical energy conversion element with a fixed phase difference, thereby exciting progressive vibration in the vibrating body;

detecting vibration generated in the vibrating body;

acquiring a phase difference profile indicative of a relationship between a position of the driven body with respect to the vibrating body in a case where relative movement between the driven body and the vibrating body is caused by the vibration excited in the vibrating body, and a phase difference between a signal produced by detecting the vibration and the first drive signal or the second drive signal;

detecting a lowest-phase difference position at which the phase difference becomes lowest, from the phase difference profile acquired by said acquiring; and

acquiring information on a relative position between the driven body and the vibrating body, and switching the first drive signal and the second drive signal applied to the electromechanical energy conversion element to a third drive signal and a fourth drive signal, respectively, based on the information on the relative position and the lowest-phase difference position, thereby changing a position at which a largest one of peaks of amplitude of the progressive vibration excited in the vibrating body is formed.