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.

1 . A voice coil motor, comprising:
 a cover comprising an upper plate and a lateral plate extending from the upper plate;   a bobbin disposed in the cover;   a coil disposed on the bobbin;   a magnet disposed between the coil and the lateral plate of the cover;   a base disposed below the bobbin and coupled to the lateral plate of the cover; and   a first elastic member coupled to the bobbin,   wherein the first elastic member comprises two elastic members spaced apart from each other,   wherein each of the two 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,   wherein the coil is electrically connected to the two elastic members,   wherein the first elastic member is configured to support the bobbin to form a first gap between the bobbin and the base and a second gap between the bobbin and the upper plate of the cover at an initial position when no current is applied to the coil, and   wherein the bobbin is disposed at the initial position so that the second gap is shorter than the first gap.   
     
     
         2 . The voice coil motor of  claim 1 , wherein the inner part of the first elastic member is disposed at a position lower than that of the outer part of the first elastic member when the bobbin is disposed at the initial position. 
     
     
         3 . The voice coil motor of  claim 1 , wherein the bobbin moves toward the base to decrease the first gap when a backward current is applied to the coil through the two elastic members. 
     
     
         4 . The voice coil motor of  claim 3 , wherein the bobbin moves toward the upper plate of the cover to decrease the second gap when a forward current is applied to the coil through the two elastic members. 
     
     
         5 . The voice coil motor of  claim 1 , wherein the coil is fixed to a periphery of the bobbin by an adhesive. 
     
     
         6 . The voice coil motor of  claim 1 , comprising:
 a second elastic member coupled to the bobbin and disposed over 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 when the bobbin is disposed at the initial position.   
     
     
         7 . The voice coil motor of  claim 6 , wherein the inner part of the second elastic member is disposed at a position lower than that of the outer part of the second elastic member when the bobbin is disposed at the initial position. 
     
     
         8 . The voice coil motor of  claim 1 , wherein at least a portion of the connection part of the second elastic member is overlapped with the upper plate of the cover in a vertical direction. 
     
     
         9 . The voice coil motor of  claim 1 , comprising:
 a spacer disposed between the magnet and the upper plate of the cover.   
     
     
         10 . The voice coil motor of  claim 1 , wherein the coil is overlapped to the magnet in a horizontal direction, and
 wherein a vertical length of the magnet is greater than a vertical length of the coil.   
     
     
         11 . The voice coil motor of  claim 1 , wherein at least a portion of the bobbin is overlapped with the upper plate of the cover and the base in a vertical direction. 
     
     
         12 . 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, and
 wherein the sill of the bobbin is overlapped with the coil in a vertical direction.   
     
     
         13 . The voice coil motor of  claim 1 , wherein the bobbin comprises a hole formed with a thread. 
     
     
         14 . 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.   
     
     
         15 . The voice coil motor of  claim 1 , A mobile terminal, comprising the camera of  claim 14 . 
     
     
         16 . A voice coil motor, comprising:
 a cover comprising an upper plate and a lateral plate extending from the upper plate;   a bobbin disposed in the cover;   a coil disposed on the bobbin;   a magnet disposed between the coil and the lateral plate of the cover;   a base disposed below the bobbin and coupled to the lateral plate of the cover; and   a first elastic member coupled to the bobbin,   wherein the first elastic member comprises two elastic members spaced apart from each other,   wherein each of the two 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,   wherein the coil is electrically connected to the two elastic members,   wherein the first elastic member is configured to support the bobbin to form a first gap between the bobbin and the base and a second gap between the bobbin and the upper plate of the cover at an initial position when no current is applied to the coil, and   wherein the inner part of the first elastic member is disposed at a position lower than that of the outer part of the first elastic member when the bobbin is disposed at the initial position.   
     
     
         17 . The voice coil motor of  claim 16 , comprising:
 a second elastic member coupled to the bobbin and disposed over 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 inner part of the second elastic member is disposed at a position lower than that of the outer part of the second elastic member when the bobbin is disposed at the initial position.   
     
     
         18 . The voice coil motor of  claim 16 , wherein the bobbin moves toward the base to decrease the first gap when a backward current is applied to the coil through the two elastic members. 
     
     
         19 . The voice coil motor of  claim 18 , wherein the bobbin moves toward the upper plate of the cover to decrease the second gap when a forward current is applied to the coil through the two elastic members. 
     
     
         20 . A method for driving a voice coil motor, comprising:
 providing a bobbin spaced apart from a base by a first gap and from a cover by a second gap 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 the first gap decreases;   moving the bobbin from the reference position by reducing the backward current such that the second gap decreases; and   stopping the bobbin at a position corresponding to an optimum focus.   
     
     
         21 . The method of  claim 20 , wherein moving the bobbin from the reference position comprises moving the bobbin past the initial position from the reference position by applying a forward current that flows in opposition to the backward current to the coil. 
     
     
         22 . The method of  claim 21 , wherein moving the bobbin from the reference position comprises increasing the forward current to the coil continuously or in a stair formation or decreasing the backward current to the coil continuously or in a stair formation. 
     
     
         23 . The method of  claim 21 , wherein 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; and   returning the bobbin to the position of the optimum focus by applying the backward current to the coil or by reducing the forward current to the coil.   
     
     
         24 . The method of  claim 21 , comprising:
 maintaining the bobbin at the position of the optimum focus by maintaining an amount of the forward current or the backward current when the optimum focus is achieved.