Voice coil motor and driving method thereof

Patent metadata

Field	Value
Publication number	US-9448383-B2
Application number	US-201113882440-A
Country	US
Kind code	B2
Filing date	Feb 22, 2011
Priority date	Nov 2, 2010
Publication date	Sep 20, 2016
Grant date	Sep 20, 2016

Abstract

A voice coil motor (VCM) is disclosed, the VCM including: a stator including a magnet generating a first electromagnetic field; a mover including a bobbin formed with a hollow hole through which light passes and a coil formed on a periphery of the bobbin that generates a second electromagnetic field responsive to the first electromagnetic field; a base fixed at the stator and formed with an opening through which the light passes; and at least one elastic member elastically supporting the bobbin and forming a gap between the bobbin and the base when the coil is not applied with a current.

First claim

The invention claimed is:

1. A method of driving a voice coil motor (VCM) that includes a stator including a magnet and a base, a mover including a bobbin and a coil block at a periphery of the bobbin, a cover coupled to the base, and an elastic member including a first elastic member and a second elastic member, wherein the first elastic member includes a first member connected to one end of the coil block and a second member connected to the other end of the coil block and separated from the first member, wherein each of the first member and the second member includes a first inner elastic unit coupled to a lower portion of the bobbin, a first outer elastic unit and a first connection elastic unit connecting the first inner elastic unit and the first outer elastic unit, and wherein the second elastic member includes a second inner elastic unit coupled to an upper portion of the bobbin, a second outer elastic unit and a second connection elastic unit connecting the second inner elastic unit and the second outer elastic unit, and wherein the elastic member is configured to support the bobbin, the method for obtaining an optimum focus comprising:
providing the mover at an initial position while no current is applied to the coil block, wherein a bottom surface of the first inner elastic unit of the first elastic member is spaced apart from the base by a first gap in a direction along or parallel to an optical axis and a top surface of the second inner elastic unit of the second elastic member is spaced apart from the cover by a second gap in the direction along or parallel to the optical axis, such that the first gap between the first inner elastic unit of the first elastic member and the base is smaller than the second gap between the second inner elastic unit of the second elastic member and the cover, and the bottom surface of the first inner elastic unit of the first elastic member is positioned below the bottom surface of the first outer elastic unit of the first elastic member in the direction along or parallel to the optical axis, and the top surface of the second inner elastic unit of the second elastic member is positioned below the top surface of the second outer elastic unit of the second elastic member in the direction along or parallel to the optical axis;
applying a backward current to the coil block of the mover in the initial position to move the mover in a first direction to a first position that a bottom surface of the bobbin approaches the base from the initial position, wherein the first direction is a direction from an upper surface of the bobbin to the bottom surface of the bobbin, such that the bottom surface of the first inner elastic unit of the first elastic member approaches the base from the initial position while a bottom surface of the first outer elastic unit of the first elastic member is stationary;
applying a forward current to the coil block after receiving the backward current to move the mover in a second direction, opposite to the first direction, toward a second position that the top surface of the second inner elastic unit of the second elastic member approaches the cover from the first position;
stopping the mover at a position past the optimum focus by increasing the forward current to the coil block;
returning the mover to a position corresponding to the optimum focus located between the first position and the second position by adjusting the forward current to the coil block; and
maintaining the mover at the position corresponding to the optimum focus by maintaining an amount of the forward current, such that the optimum focus is formed.

2. The method of claim 1 , wherein in the applying of the backward current to the coil block the first gap is decreased while the bobbin moves to the first position, and then in the applying of the forward current to the coil block the first gap is increased while the bobbin moves toward the second position.

3. The method of claim 1 , wherein in the applying of the backward current to the coil block the second gap is increased and the first gap is decreased, and in the applying of the forward current to the coil block the second gap is decreased and the first gap is increased.

4. The method of claim 1 , wherein the VCM is embedded in a camera comprising a lens coupled to the bobbin and an image sensor.

5. The method of claim 4 , wherein the camera is embedded in a mobile phone.

6. The method of claim 1 , wherein the bobbin is moved past the initial position from the first position as the backward current is reduced, and then the forward current is increased.

7. The method of claim 1 , wherein a lens is coupled to the bobbin and the bobbin is supported by the first and second elastic members such that the bobbin is disposed at the initial position spaced from the base when stationary, the bobbin is to approach the base when the backward current is provided to the coil block at the initial position, and then a separation between the bobbin and the base is increased by reducing the backward current or providing the forward current flowing in a direction opposite of the backward current, wherein the bobbin is stopped when the optimum focus is formed between the lens and an image sensor.

8. The method of claim 1 , wherein the elastic member supports the mover at the initial position, by providing the first gap between the bottom surface of the first inner elastic unit of the first elastic member and an upper surface of the base and by providing the second gap between the top surface of the second inner elastic unit of the second elastic member and an inner surface of the upper plate of the cover.

9. The method of claim 1 , wherein in the returning of the mover the bobbin is moved to the position corresponding to the optimum focus by reducing the forward current to the coil block.

10. A method of driving a voice coil motor (VCM) that includes a stator including a magnet and a base, a mover including a bobbin and a coil block at a periphery of the bobbin, a cover coupled to the base, and an elastic member including a first elastic member and a second elastic member, wherein the first elastic member includes a first member connected to one end of the coil block and a second member connected to the other end of the coil block and separated from the first member, wherein each of the first member and the second member includes a first inner elastic unit coupled to a lower portion of the bobbin, a first outer elastic unit and a first connection elastic unit connecting the first inner elastic unit and the first outer elastic unit, and wherein the second elastic member includes a second inner elastic unit coupled to an upper portion of the bobbin, a second outer elastic unit and a second connection elastic unit connecting the second inner elastic unit and the second outer elastic unit, and wherein the elastic member is configured to support the bobbin, the method for obtaining an optimum focus comprising:
providing the mover at an initial position while no current is applied to the coil block, wherein a bottom surface of the first inner elastic unit of the first elastic member is spaced apart from the base by a first gap in a direction along or parallel to an optical axis and a top surface of the second inner elastic unit of the second elastic member is spaced apart from the cover by a second gap in the direction along or parallel to the optical axis, such that the first gap between the first inner elastic unit of the first elastic member and the base is smaller than the second gap between the second inner elastic unit of the second elastic member and the cover, and the bottom surface of the first inner elastic unit of the first elastic member is positioned below the bottom s

Assignees

• Park Sangok
• Lg Innotek Co Ltd

Inventors

• Park Sangok

Classifications

• H02K41/0356 Primary

  moving along a straight path · CPC title

• H02P25/034

  Voice coil motors (voice coil motors driven by DC H02P7/025) · CPC title

• H02K33/18 Primary

  with coil systems moving upon intermittent or reversed energisation thereof by interaction with a fixed field system, e.g. permanent magnets · CPC title

• G02B7/08 Primary

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

• H02P25/06

  Linear motors · CPC title