Drive mechanism employing electromechanical transducer, photographing lens with the drive mechanism, and its drive circuit

• US 6,249,093 B1
• Filed: 06/07/1999
• Issued: 06/19/2001
• Est. Priority Date: 06/08/1998
• Status: Expired due to Term

• Current Assignee: Minolta Corporation Limited (Konica Minolta Inc.)
• Original Assignee: Minolta Corporation Limited (Konica Minolta Inc.)
• Inventors: Takahata, Junji, Kawabe, Koutaro
• Primary Examiner(s): Ramirez, Nestor
• Assistant Examiner(s): JONES, JUDSON
• Application Number:
  US09/326,875
• Time in Patent Office: 743 Days
• Field of Search: 318/118, 318/119, 318/122, 318/123, 318/126, 318/129, 318/135, 310/316, 310/317, 310/323.02, 310/328
• US Class Current: 318/129
• CPC Class Codes: H02N 2/025 Inertial sliding motors
• CPC Class Codes: H02N 2/062 Small signal circuits; Means for controlling position or derived quantities, e.g. for removing hysteresis
• CPC Class Codes: H02N 2/067 generating drive pulses

Abstract

A driving apparatus, employing a piezoelectric element, for smoothly and silently driving a focus lens of a camera over a wide range of its driving speed. The driving apparatus includes a control system for controlling the piezoelectric element in such a manner that a continuous supply of a certain number of drive pulses to the piezoelectric element and a non-supply thereof during a certain period of time are repeated by a “block pulse drive” at time of slow speed driving, and that the continuous supply thereof are continuously supplied to the piezoelectric element by a “continuous pulse drive” at time of high speed driving.

Claims

1. A drive mechanism, comprising:

an electromechanical transducer;

a pulse supplier for providing an electrical charge and inducing discharge of the electrical charge relative to the electromechanical transducer, wherein the pulse supplier supplies a drive pulse to the electromechanical transducer so that the electromechanical transducer expands at a first velocity and contracts at a second velocity, and so that a moving body driven by the electromechanical transducer is moved in a predetermined direction; and

a controller which has a first mode for controlling the pulse supplier, wherein in the first mode the controller controls the pulse supplier so that a pulse supply period, in which a specified number of pulses of the drive pulse are continuously supplied from the pulse supplier to the electromechanical transducer, and a pulse non-supply period, in which the drive pulse is not supplied from the pulse supplier to the electromechanical transducer, are alternately repeated.

2. A drive mechanism as claimed in claim 1, wherein the controller determines a target velocity of the moving body, in which the controller changes the pulse non-supply period, during which the drive pulse is not supplied from the pulse supplier to the electromechanical transducer, on a basis of the target velocity thus determined.

3. A drive mechanism as claimed in claim 1, which further comprises a detector for detecting a movement amount of the moving body,

wherein the controller changes the specified number of pulses of the drive pulse supplied by the pulse supplier during a pulse supply period, on a basis of the movement amount detected by the detector, so that the movement amount, corresponding to one cycle defined by the pulse supply period and the pulse non-supply period, of the moving body is adjusted to a specified amount.

4. A drive mechanism as claimed in claim 2, wherein the controller changes the specified number of pulses of the drive pulse supplied by the pulse supplier during the pulse supply period on a basis of the target velocity.

5. A drive mechanism as claimed in claim 3, wherein the controller changes the pulse non-supply period, during which the drive pulse is not supplied from the pulse supplier to the electromechanical transducer, on the basis of the movement amount detected by the detector.

6. A drive mechanism as claimed in claim 2, wherein the controller determines the target velocity of the moving body so that the target velocity decreases in steps as the moving body approaches a target stop position.

7. A drive mechanism as claimed in claim 2, wherein the controller makes the target velocity of the moving body correspond to an operation velocity of an operational member.

8. A drive mechanism as claimed in claim 1, wherein the controller further has a second mode for controlling the pulse supplier so that pulses of the drive pulse are continuously supplied from the pulse supplier to the electromechanical transducer, and

wherein the controller selects one of the first mode and the second mode.

9. A drive mechanism as claimed in claim 8, wherein the controller sets a reference velocity based on which mode of the first mode and the second mode the controller has selected, the reference velocity being a reference point at which the controller switches to the other one of the first mode and the second mode.

10. A drive mechanism as claimed in claim 8, wherein the controller determines a target velocity of the moving body, and

wherein the controller selects the second mode when the target velocity is relatively higher, and the controller selects the first mode when the target velocity is relatively lower.

11. An auto-focus photographing lens with a drive mechanism, the drive mechanism comprising:

an electromechanical transducer;

a pulse generator for providing an electrical charge and inducing discharge of the electrical charge relative to the electromechanical transducer, wherein the pulse generator supplies a drive pulse to the electromechanical transducer so that the electromechanical transducer expands at a first velocity and contracts at a second velocity, and so that a moving body driven by the electromechanical transducer is moved in a predetermined direction; and

a controller for controlling the pulse generator so that a pulse supply period, in which a specified number of pulses of the drive pulse are continuously supplied from the pulse generator to the electromechanical transducer, and a pulse non-supply period, in which the drive pulse is not supplied from the pulse generator to the electromechanical transducer, are alternately repeated,

wherein the moving body moves a focus lens.

12. A power-focus photographing lens with a drive mechanism, the drive mechanism comprising:

an electromechanical transducer;

a pulse supplier for providing an electrical charge and inducing discharge of the electrical charge relative to the electromechanical transducer, wherein the pulse supplier supplies a drive pulse to the electromechanical transducer so that the electromechanical transducer expands at a first velocity and contracts at a second velocity, and so that a moving body driven by the electromechanical transducer is moved in a predetermined direction; and

a controller for controlling the pulse supplier so that a pulse supply period, in which a specified number of pulses of the drive pulse are continuously supplied from the pulse supplier to the electromechanical transducer, and a pulse non-supply period, in which the drive pulse is not supplied from the pulse supplier to the electromechanical transducer, are alternately repeated,

wherein the controller determines a target velocity of the moving body, in which the controller changes the pulse non-supply time, during which the drive pulse is not supplied from the pulse supplier to the electromechanical transducer, on a basis of the target velocity thus determined,

wherein the controller makes the target velocity of the moving body correspond to an operation velocity of an operational member,

wherein the moving body moves a focus lens, and

wherein the operational member is a member for adjusting a focus of the focus lens.

13. A drive mechanism having a drive circuit, the drive mechanism comprising:

an electromechanical transducer; and

a pulse supply section for providing an electrical charge and inducing discharge of the electrical charge relative to the electromechanical transducer, wherein the pulse supply section supplies a drive pulse to the electromechanical transducer so that the electromechanical transducer expands at a first velocity and contracts at a second velocity, and so that a moving body driven by the electromechanical transducer is moved in a predetermined direction,

wherein the drive circuit has a control section for controlling the pulse supply section so that a pulse supply period, in which a specified number of pulses of the drive pulse are continuously supplied from the pulse supply section to the electromechanical transducer, and a pulse non-supply period, in which the drive pulse is not supplied from the pulse supply section to the electromechanical-transducer, are alternately repeated.

14. An auto-focus photographing lens with a drive mechanism, the drive mechanism comprising:

an electromechanical transducer;

a pulse supplier for providing an electrical charge and inducing discharge of the electrical charge relative to the electromechanical transducer, wherein the pulse supplier supplies a drive pulse to the electromechanical transducer so that the electromechanical transducer expands at a first velocity and contracts at a second velocity, and so that a moving body driven by the electromechanical transducer is moved in a predetermined direction; and

a controller which has a first mode for controlling the pulse supplier so that a pulse supply period, in which a specified number of pulses of the drive pulse are continuously supplied from the pulse supplier to the electromechanical transducer, and a pulse non-supply period, in which the drive pulse is not supplied from the pulse supplier to the electromechanical transducer, are alternately repeated,

wherein the controller further has a second mode for controlling the pulse supplier so that pulses of the drive pulse are continuously supplied from the pulse supplier to the electromechanical transducer,

wherein the controller selects one of the first mode and the second mode, and

wherein the moving body moves a focus lens.

15. A power-focus photographing lens with a drive mechanism, the drive mechanism comprising:

an electromechanical transducer;

a pulse supplier for providing an electrical charge and inducing discharge of the electrical charge relative to the electromechanical transducer, wherein the pulse supplier supplies a drive pulse to the electromechanical transducer so that the electromechanical transducer expands at a first velocity and contracts at a second velocity, and so that a moving body driven by the electromechanical transducer is moved in a predetermined direction; and

a controller which has a first mode for controlling the pulse supplier so that a pulse supply period, in which a specified number of pulses of the drive pulse are continuously supplied from the pulse supplier to the electromechanical transducer, and a pulse non-supply period, in which the drive pulse is not supplied from the pulse supplier to the electromechanical transducer, are alternately repeated,

wherein the controller further has a second mode for controlling the pulse supplier so that pulses of the drive pulse are continuously supplied from the pulse supplier to the electromechanical transducer,

wherein the controller selects one of the first mode and the second mode, and

wherein the moving body drives a focus lens in which a movement of the moving body corresponds to a movement of an operational member.

16. A drive mechanism having a drive circuit, the drive mechanism comprising:

an electromechanical transducer; and

a pulse supply section for providing an electrical charge and inducing discharge of the electrical charge relative to the electromechanical transducer, wherein the pulse supply section supplies a drive pulse to the electromechanical transducer so that the electromechanical transducer expands at a first velocity and contracts at a second velocity, and so that a moving body driven by the electromechanical transducer is moved in a predetermined direction,

wherein the drive circuit comprises a control section which has a first mode for controlling the pulse supply section so that a pulse supply period, in which a specified number of pulses of the drive pulse are continuously supplied from the pulse supply section to the electromechanical transducer, and a pulse non-supply period, in which the drive pulse is not supplied from the pulse supply section to the electromechanical transducer, are alternately repeated,

wherein the control section further has a second mode for controlling the pulse supply section so that pulses of the drive pulse are continuously supplied from the pulse supply section to the electromechanical transducer, and

wherein the control section selects one of the first mode and the second mode.