Abstract:
A voice coil motor includes an outer shell, a moveable frame, a coil of wire, a number of magnetic members and a first elastic member. The outer shell includes a number of sidewalls connected to each other end-to-end. The moveable frame is moveably received in the outer shell. The coil of wire is wrapped around the moveable frame and is received in the outer shell. Each of the magnetic members is attached to a corner formed by two inner surfaces of two adjacent sidewalls. The magnetic members and the coil of wire are configured for cooperating to drive the movable frame to move in the outer shell. The first elastic member is attached to the moveable frame and received in the outer shell. The first elastic member is configured for providing an elastic restoring force.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to motors, and particularly to a voice coil motor and a camera module having the same. 
     2. Description of Related Art 
     Voice coil motors (VCMs) are widely used, for example, as lens actuators in camera modules. Camera modules have become miniaturized over time, and thus VCMs are correspondingly being required to be made smaller and smaller. 
     A typical VCM includes an outer shell housing one or more magnets fixed to a frame, a moveable frame wrapped by a coil of wire, and one or two elastic members connected between the lens retainer and the frame. The immovable frame is movable in the outer shell due to an interaction between the coil of wire and the magnetic members. 
     However, with the above configuration, too many elements are needed for the VCM. In addition, when the VCM is used in a camera module, a base is also needed for accommodating an image sensor, thus the entire camera module is not as compact as it could be. 
     What is needed, therefore, is a voice coil motor and a camera module, which can overcome the above shortcomings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a voice coil motor in accordance with a first embodiment. 
         FIG. 2  is an exploded view of the voice coil motor of  FIG. 1 . 
         FIG. 3  is a sectional view of the voice coil motor shown in  FIG. 1 , taken along line III-III. 
         FIG. 4  is a schematic view of the voice coil motor of  FIG. 2  partially assembled. 
         FIG. 5  is a sectional view of a camera module in accordance with a second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present voice coil motor (VCM) and camera module will now be described in detail and with reference to the drawings. 
     Referring to  FIGS. 1 to 3 , a VCM  100  in accordance with a first embodiment is provided. The VCM  100  mainly includes an outer shell  10 , a spacer  90 , an upper elastic member (first elastic member)  30 , four magnetic members  40 , a movable frame  60 , a coil of wire  62 , a lower elastic member (second elastic member)  70 , and a base  80 . 
     The outer shell  10  is substantially square in horizontal section and includes a top plate  15 , a first sidewall  11 , a second sidewall  12 , a third sidewall  13  and a fourth sidewall  14 . The first side wall  11  opposes the third sidewall  13 . The first sidewall  11  is substantially perpendicular to the second sidewall  12  and the fourth sidewall  14 . The second sidewall  12  is substantially perpendicular to the first sidewall  11  and the third sidewall  13 . The first sidewall  11  and the third sidewall  13  connect the second and fourth sidewalls  12 ,  14 . The second sidewall  12  opposes the fourth sidewall  14 . The first, second, third and fourth sidewalls  11 ,  12 ,  13 ,  14  are connected to the four respective edges of the top plate  15 . The first, second, third and fourth sidewalls  11 ,  12 ,  13 ,  14  and the top plate  15  cooperatively form a space  300  receiving the moveable frame  60 , the coil of wire  62 , the magnetic members  40 , the upper elastic member  30  and the lower elastic member  70  therein. A first through hole  16  is defined in the center of the top plate  15 . The first through hole  16  is in communication with the space  300 . A projection  110  is formed at a lower edge of each of the first sidewall  11  and the third sidewall  13 . The outer shell  10  is made of ferromagnetic materials. 
     The four magnetic members  40  are permanent magnets and configured for generating a magnetic field in the outer shell  10 . Each of the four magnetic members  40  is substantially a triangular prism. Referring to  FIGS. 2 and 4 , one of the four magnetic members  40  is taken as an example in describing the manner of attachment of the magnetic members  40 . The four magnetic member  40  include a first side surface  41  and a second side surface  42  connected perpendicularly to the first side surface  42  in this embodiment. The first sidewall  11  includes a first inner surface  111 . The second sidewall  12  includes a second inner surface  121 . The first side surface  41  is attached to the first inner surface  111  and the second side surface  42  is attached to the second inner surface  121  so that the magnetic member  40  is attached to a corner  91  formed by two inner surfaces  111 ,  121  of two adjacent sidewalls  11 ,  12 . Therefore, the four magnetic members  40  are directly secured to the outer shell  10  rather than requiring an extra fixing frame. Therefore, the VCM  100  is compact. 
     The upper elastic member  30  is substantially plate-shaped. A second through hole  33  is defined in the center of the upper elastic member  30 . The upper elastic member  30  includes an elastic portion  32 , and a rigid portion  31  surrounding the elastic portion  32 . The elastic portion  32  and the rigid portion  31  flank the second through hole  33 . The elastic portion  32  is adjacent to the second through hole  33  and the rigid portion  31  forms an outer frame for the elastic portion  32 . The spacer  90  is rectangular-shaped and is sandwiched between the rigid portion  31  and the top plate  15 . The four magnetic members  40  urge the upper elastic member  30  against the spacer  90  to retain the upper elastic member  30  in place. The spacer  90  provides a sufficient space for necessary movement or deformation of the elastic portion  32 . 
     For ease in assembling the VCM  100 , the outer shell  10  includes a number of protrusions  17 . The protrusions  17  depend from an inner edge of the top plate  15  and into the first through hole  16 . Cutouts  34  are defined in the upper elastic member  30 . The protrusions  17  extend through the upper elastic member  30  through the cutouts  34  and server as a magnetic flux guide meaning. 
     The movable frame  60  is substantially a moveable lining. A threaded through hole  611  is defined in a center of the moveable frame  60 . A lens unit  210  (see  FIG. 5 ) is threadedly received in the threaded through hole  611 . The coil of wire  60  is wrapped around the moveable frame  60 . 
     The lower elastic member  70  is an electric conductor and includes a third through hole, an elastic portion and a rigid portion (not labeled) similar to those of the upper elastic member  30 . The difference between the lower elastic member  70  and the upper elastic member  30  is that the lower elastic member  70  is diametrically divided, consisting of a first part  71  and a separate second part  72 . A first lead  711  extends from the first part  71  and a second lead  712  extend from the second part  72 . The first lead  711 , the first part  71 , the coil of wire  62 , the second part and the second lead  712  are connected in series. Therefore, the first lead  711  and the second lead  712  can be connected to a power supply (not shown). In this way, the coil of wire  62  can be charged and generate a magnetic field. A number of positioning through holes  73  are defined in the four corners of the lower elastic member  70 . 
     The elastic portions of the upper elastic member  30  and the lower elastic member  70  are respectively attached to the upper and lower ends (opposite ends) of the moveable frame  60 . The upper elastic member  30  and/or the lower elastic member  70  return the moveable frame  60  to a resting position when the coil of wire  62  is not energized. 
     A fourth through hole  81  is defined in a center of the base, having a size substantially the same as that of the threaded through hole  611 . The base  80  further has a number of posts  82  thereon. The post  82  are intended for engagement in the positioning through holes  73  of the lower elastic member  70 , and glue or other fixative may be applied thereon to further secure the lower elastic member  70  to the base  80 . A first recess  84  is defined in a first side  831  of the base  80  corresponding to the first sidewall  11  and a second recess (not labeled) is defined in a second side  832  of the base  80  corresponding to the third sidewall  13 . When the base  80  is impressed into the outer shell  10 , the projections  110  are engaged in the first recess  84  and the second recess so that the base  80  is attached to the outer shell  10 . Glue or some other means of fixation may be applied to the projections  110 , the first recess  84  and the second recess to further secure the base  80  into the outer shell  10 . 
     In operation, the movable frame  60  is movable upwards and downwards along the central axis L of the moveable frame  60  in the outer shell  10  due to the interaction between the charged coil of wire  62  and the magnetic members  40 , and is immobile between the upper and lower elastic members  30 ,  70  when the coil of wire  62  is not energized. 
     In alternative embodiments, the upper elastic member  30  can be further secured by glue or bolts. The spacer  90  can be omitted and a thickness of the rigid portion  31  can be made greater than that of the elastic portion  32  to provide sufficient space for movement or deformation of the elastic portion  32 . The structure of the lower elastic member  70  may be the same as that of the upper elastic member  30 , and the first lead  711  and the second lead  712  can be isolated from the lower elastic member  70 . The first lead  711 , the coil of wire  62  and the second lead  712  are connected in series. 
     Referring to  FIG. 5 , a camera module  200  in accordance with a second embodiment, is provided. The camera module  200  includes the VCM  100  of the first embodiment, a lens unit  210  and an image sensor  240 . 
     The optical axis O of the lens unit  210  coincides with the central axis L of the moveable frame  60 . The lens unit  210  is secured in the moveable frame  60 . The lens unit  210  includes a lens group  220  and a lens barrel  230 . The lens group  220  in the lens barrel  230  may include one or more lenses. The lens barrel  230  is externally threaded and engagable with the interior thread of the moveable frame  60 . The lens unit  210  in the lens barrel  230  protects and covers the image sensor  240 , which is accommodated in the base  80 , and thus no separate base for the image sensor  240  is required, therefore the entire camera module  200  is compact. 
     In operation, the movable frame  60  together with the lens unit  210  is movable upwards and downwards along the central axis L of the moveable frame  60  (optical axis O of the lens unit  210 ) in the outer shell  10  due to the interaction between the charged coil of wire  62  and the magnetic members  40 . 
     In alternative embodiments, the lens unit  210  may further include a lens holder coupled to the lens barrel  230  and the image sensor  240  may be affixed in the lens holder rather than in the base  80 . The lens barrel  230  may be omitted and the lens group  220  may be directly attached to the inner wall of the moveable frame  60 . In addition, the shape of the outer shell  10  and the base  80  may be different, and the number of the magnetic members  40  may vary. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.