Drive device for a vibration actuator having a control circuit to control charge and discharge of an electromechanical conversion element

• US 5,734,236 A
• Filed: 11/15/1996
• Issued: 03/31/1998
• Est. Priority Date: 11/15/1995
• Status: Expired due to Term

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Motegi, Kiyoshi
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): JONES, JUDSON
• Application Number:
  US08/749,676
• Time in Patent Office: 501 Days
• Field of Search: 318/114, 318/127, 318/128, 318/126, 318/129, 318/130, 310/317
• US Class Current: 318/114
• CPC Class Codes: H02N 2/14 Drive circuits; Control arrangements or methods
• 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 2/145 Large signal circuits, e.g. final stages
• CPC Class Codes: H02N 2/163 Motors with ring stator

Abstract

A drive device for a vibration motor which provides constant efficient driving with a simple circuit and control sequence. The drive device for the vibration motor includes a charging circuit which impresses a predetermined voltage on an electromechanical energy conversion element, a discharge circuit which causes discharge of the electromechanical energy conversion element via an inductive element, a control circuit which alternately connects the charging circuit or the discharge circuit to the electromechanical energy conversion element, and a period detection circuit which detects the period of the resonant frequency of a circuit formed by the electromechanical energy conversion element and the inductive element. The control circuit causes an increase and a decrease of the interval the discharge circuit is connected, such that the interval of connection of the discharge circuit and the period detected by the period detection circuit become equal, causing the drive frequency of the vibration motor to change.

Claims

1. A drive device for a vibration motor having an electromechanical energy converting element which converts electrical energy into mechanical energy, comprising:

a charging circuit to provide electrical energy to the electromechanical energy converting element by impressing a predetermined voltage on the electromechanical energy converting element;

a discharge circuit to generate mechanical energy in the electromechanical energy converting element, by causing the electromechanical energy converting element, which has been supplied with electrical energy, to discharge via an inductive element;

a control circuit to alternately connect the discharge circuit to the electromechanical energy converting element for a period which depends on the inductance characteristics of the inductive element, and to connect the charging circuit to the electromechanical energy converting element for a period which does not depend on the inductance characteristics of the inductive element; and

a period detection circuit to detect a period of resonant vibration of the electromechanical energy converting element and the inductive element, wherein

the control circuit controls the connection of the discharge circuit and the charging circuit so that the period for which the discharge circuit is connected to the electromechanical energy converting element is equal to the period detected by the period detection circuit, and changes the drive frequency of the vibration motor by increasing and decreasing the period for which the charging circuit is connected to the electromechanical energy converting element.

2. A drive device for a vibration motor as recited in claim 1, wherein the period detection circuit detects the period of resonant vibration by detecting a maximum value of the voltage change in the discharge circuit or the electromechanical energy converting element.

3. A drive device for a vibration motor having an electromechanical energy converting element which converts electrical energy into mechanical energy, comprising:

a charging circuit to provide electrical energy to the electromechanical energy converting element by impressing a predetermined voltage on the electromechanical energy converting element;

a discharge circuit to generate mechanical energy in the electromechanical energy converting element, by causing the electromechanical energy converting element, which has been supplied with electrical energy, to discharge via an inductive element; and

a control circuit to alternately connect the discharge circuit to the electromechanical energy converting element for a period which depends on the inductance characteristics of the inductive element, and to connect the charging circuit to the electromechanical energy converting element for a period which does not depend on the inductance characteristics of the inductive element, wherein

the control circuit is capable of detecting the voltage change of the electromechanical energy converting element, and

after the discharge circuit is connected to the electromechanical energy converting element, when a maximum voltage value of the electromechanical energy converting element is detected, the charging circuit is connected to the electromechanical energy conversion element.