Voice coil motor and driving method thereof

Patent metadata

Field	Value
Publication number	US-2016356982-A1
Application number	US-201615241833-A
Country	US
Kind code	A1
Filing date	Aug 19, 2016
Priority date	Nov 2, 2010
Publication date	Dec 8, 2016
Grant date	—

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

1 . A voice coil motor (VCM) for a camera, the VCM comprising:
a base formed with an opening; a mover comprising a bobbin formed with an opening and a coil block disposed on a periphery of the bobbin; a magnet for interacting with the coil block; an elastic member supporting the bobbin and comprising a first elastic member coupled to a lower portion of the bobbin and a second elastic member coupled to a upper portion of the bobbin; and a cover comprising an upper plate centrally formed with an opening and a lateral plate extending from an edge of the upper plate towards the base, wherein the elastic member supports the bobbin such that, at an initial position when no current is applied to the coil block, a first gap is present between the bobbin and the base and a second gap is present between the bobbin and the cover, wherein the mover is stationary at the initial position and spaced apart from both the base and the cover when no current is applied to the coil block, wherein the mover is configured to be driven downwardly along an optical axis to decrease the first gap when a backward current is applied to the coil block at the initial position, and the mover is configured to be driven upwardly along the optical axis upwardly to decrease the second gap when a forward current is applied to the coil block at the initial position, wherein the first elastic member comprises a first inner elastic unit coupled to 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, wherein the second elastic member comprises a second inner elastic unit coupled to 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, wherein, at the initial position when no current is applied to the coil block, the first inner elastic unit of the first elastic member is at a position lower than that of the first outer elastic unit of the first elastic member, and wherein, at the initial position when no current is applied to the coil block, the second inner elastic unit of the second elastic member is at a position lower than that of the second outer elastic unit of the second elastic member.

2 . The VCM of claim 1 , wherein the first elastic member includes a first connection member connected to a first distal end of a wire of the coil block and a second connection member connected to a second distal end of the wire of the coil block, and wherein the first connection member of the first elastic member is spaced apart from the second connection member of the first elastic member.

3 . The VCM of claim 1 , wherein the first gap is smaller than the second gap at the initial position.

4 . The VCM of claim 1 , further comprising a yoke, wherein the yoke comprises a yoke upper plate and a yoke lateral plate extended from an edge of the yoke upper plate.

5 . The VCM of claim 1 , wherein the second outer elastic unit of the second elastic member is arranged below the upper plate of the cover.

6 . The VCM of claim 1 , wherein the bobbin is configured to: move in a first direction and make contact with an upper surface of the base; and move in a second direction opposite to the first direction and make contact with the upper plate of the cover.

7 . The VCM of claim 1 , wherein the first inner elastic unit of the first elastic member is configured to move relative to the base by extension of the first connection elastic unit while the first outer elastic unit is fixed, and wherein the second inner elastic unit of the second elastic member is configured to move relative to the base by extension of the second connection elastic unit while the second outer elastic unit is fixed.

8 . The VCM of claim 1 , wherein the bobbin comprises a thread for fixing a lens.

9 . The VCM of claim 1 , further comprising at least one of the following: a first shock absorption member on an upper surface of the base and facing the bobbin; and a second shock absorption member on a lower surface of the upper plate of the cover and facing the bobbin.

10 . A camera module, comprising:
a lens; an image sensor; and the VCM of claim 1 , wherein the VCM adjusts a distance between the image sensor and the lens.

11 . The camera of claim 10 , wherein the camera module further comprises;
a control unit to generate an ascending control signal for ascending the bobbin and a descending control signal for descending the bobbin, and a current providing unit providing the forward current to the coil block in response to the ascending control signal and providing the backward current to the coil block in response to the descending control signal.

12 . A method for driving a voice coil motor (VCM), wherein the VCM comprises:
a magnet; a base; a mover comprising a bobbin and a coil block wound on the bobbin; an elastic member for supporting the bobbin; and a cover for covering the mover, wherein the elastic member comprises a first elastic member coupled to a lower portion of the bobbin and a second elastic member coupled to an upper portion of the bobbin, wherein the first elastic member comprises a first inner elastic unit coupled to 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, wherein, at an initial position when no current is applied to the coil block, the first inner elastic unit of the first elastic member is at a position lower than that of the first outer elastic unit of the first elastic member, and wherein, at the initial position when no current is applied to the coil block, the second inner elastic unit of the second elastic member is at a position lower than that of the second outer elastic unit of the second elastic member, the method comprising: providing the bobbin at the initial position spaced apart from the base by a first gap and from the cover by a second gap when no current is applied to the coil block; moving the bobbin downwardly from the initial position to a reference position by applying a backward current to the coil block such that the first gap decreases and the second gap increases; moving the bobbin upwardly from the reference position by reducing the backward current and then applying a forward current that flows in opposition to the backward current to the coil block, such that the bobbin moves past the initial position from the reference position and such that the first gap increases and the second gap decreases; and stopping the bobbin at a position corresponding to an optimum focus.

13 . The method of claim 12 , wherein the step of upwardly moving the bobbin from the reference position comprises increasing the forward current to the coil block continuously or in a stair formation or decreasing the backward current to the coil block continuously or in a stair formation.

14 . The method of claim 12 , wherein the step of stopping the bobbin at the position corresponding to the optimum focus comprises:
moving the bobbin to be deviated from the position of the optimum focus by increasing the forward current to the coil block; and returning the bobbin to the position corresponding to the optimum focus by applying the backward current to the coil block or by reducing the forward current to the coil block.

15 . The method of claim 12 , further comprising
maintaining the bobbin at the position corresponding to the optimum focus by maintaining an amount of the forward current or the backward current when the optimum focus is achieve

Assignees

• Lg Innotek Co Ltd

Inventors

• Park Sangok

Classifications

• H02K41/0356 Primary

  moving along a straight path · CPC title

• H02P7/18

  by master control with auxiliary power · CPC title

• G02B7/09

  adapted for automatic focusing or varying magnification · CPC title

• G02B7/08 Primary

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

• G02B7/04

  with mechanism for focusing or varying magnification · CPC title