Voice coil motor and driving method thereof

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.

What is claimed is: 
     
         1 . A voice coil motor, comprising:
 a base;   a cover comprising an upper plate and a lateral plate;   a bobbin disposed in the cover;   a coil and a magnet configured to move the bobbin in an optical axis direction; and   a first elastic member coupled with the bobbin,   wherein the first elastic member is configured to support the bobbin to be spaced apart from both the base and the upper plate of the cover.   
     
     
         2 . The voice coil motor of  claim 1 , comprising a first shock absorption member disposed between the coil and the base. 
     
     
         3 . The voice coil motor of  claim 2 , wherein the first shock absorption member directly faces the first elastic member with no elements disposed between the first shock absorption member and the first elastic member. 
     
     
         4 . The voice coil motor of  claim 1 , wherein the base comprises a coupling pillar protruding from each of four corner areas of an upper surface of the base, and
 wherein an upper end of the coupling pillar is closer to the upper plate of the cover than is an upper end of the coil.   
     
     
         5 . The voice coil motor of  claim 1 , wherein the first elastic member comprises two first elastic members,
 wherein each of the two first elastic members comprises an inner part coupled to the bobbin, an outer part coupled to the base, and a connection part connecting the inner part and the outer part, and   wherein the coil is electrically connected to the two first elastic members.   
     
     
         6 . The voice coil motor of  claim 5 , wherein the inner part of the first elastic member is disposed lower than the outer part of the first elastic member at an initial position in a state that no current is applied to the coil. 
     
     
         7 . The voice coil motor of  claim 1 , comprising a second elastic member coupled to the bobbin and disposed above the first elastic member,
 wherein the second elastic member comprises an inner part coupled to the bobbin, an outer part disposed between the magnet and the upper plate of the cover, and a connection part connecting the inner part of the second elastic member and the outer part of the second elastic member, and   wherein the connection part of the second elastic member is spaced apart from the upper plate of the cover.   
     
     
         8 . The voice coil motor of  claim 7 , wherein the inner part of the second elastic member is disposed lower than the outer part of the second elastic member at an initial position in a state that no current is applied to the coil. 
     
     
         9 . The voice coil motor of  claim 7 , wherein at least a portion of the connection part of the second elastic member is overlapped with the upper plate of the cover in the vertical direction. 
     
     
         10 . The voice coil motor of  claim 1 , wherein the bobbin comprises a sill extending from a lower portion of a periphery of the bobbin and disposed under the coil,
 wherein the sill of the bobbin is overlapped with the coil in the optical axis direction, and   wherein, in the optical axis direction, a length of the magnet is greater than a length of the coil.   
     
     
         11 . The voice coil motor of  claim 2 , comprising:
 a second shock absorption member disposed on a lower surface of the upper plate and facing an upper surface of the bobbin; and   an upper spacer disposed between the magnet and the upper plate of the cover,   wherein the magnet is not overlapped with the coil in the optical axis direction, and   wherein the first shock absorption member comprises a resin.   
     
     
         12 . The voice coil motor of  claim 1 , wherein the bobbin is formed at an inner surface with a screw thread. 
     
     
         13 . The voice coil motor of  claim 1 , wherein the bobbin is configured to be spaced apart from the base by a first gap and from the cover by a second gap at an initial position when no current is applied to a coil, and
 wherein the bobbin is configured to move downwardly from the initial position to a reference position by applying a backward current to the coil such that the first gap decreases and the second gap increases.   
     
     
         14 . The voice coil motor of  claim 13 , wherein the bobbin is configured to move 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 such that the first gap increases and the second gap decreases and such that the bobbin moves past the initial position from the reference position. 
     
     
         15 . A camera, comprising:
 an image sensor;   the voice coil motor of  claim 1 ; and   a lens coupled to the bobbin of the voice coil motor and spaced apart from the image sensor.   
     
     
         16 . A mobile terminal, comprising the camera of  claim 15 . 
     
     
         17 . A method for driving a voice coil motor, comprising steps of:
 providing a bobbin spaced apart from both a base and a cover at an initial position when no current is applied to a coil;   moving the bobbin from the initial position to a reference position by applying a backward current to the coil such that a gap between the bobbin and the base decreases;   moving the bobbin from the reference position by reducing the backward current to the coil such that the gap between the bobbin and the base increases; and   stopping the bobbin at a position corresponding to an optimum focus.   
     
     
         18 . The method of  claim 17 , wherein the step of stopping the bobbin at the position corresponding to the optimum focus comprises:
 moving the bobbin past a position of the optimum focus by reducing the backward current to the coil; and   returning the bobbin to the position of the optimum focus by increasing the backward current to the coil.   
     
     
         19 . A method for driving a voice coil motor, comprising steps of:
 providing a bobbin spaced apart from both a base and a cover at an initial position when no current is applied to a coil;   moving the bobbin from the initial position to a reference position by applying a backward current to the coil such that a gap between the bobbin and the base decreases;   moving the bobbin from the reference position by reducing the backward current and then applying a forward current to the coil such that the gap between the bobbin and the base increases and such that the bobbin moves past the initial position; and   stopping the bobbin at a position corresponding to an optimum focus,   wherein the forward current flows in opposition to the backward current.   
     
     
         20 . The method of  claim 19 , wherein the step of stopping the bobbin at the position corresponding to the optimum focus comprises:
 moving the bobbin past a position of the optimum focus by increasing the forward current to the coil; and   returning the bobbin to the position of the optimum focus by reducing the forward current to the coil.