Abstract:
To provide a lens driving apparatus that drives a lens in its optical axis-direction without inclining it, and a lens driving apparatus that drives a bobbin in the optical axis-direction smoothly without increasing the frictional force between a ball arranged between the bobbin and a cover, and the bobbin and cover while maintaining high driving power. The lens driving apparatus comprises the polygonal cylindrical bobbin that houses the lens, the box-shaped cover that receives the bobbin, a drive unit that moves the bobbin in the optical axis-direction of the lens, and a support unit that supports the bobbin.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to a lens driving apparatus that drives a lens. 
         [0003]    The contents of the following Japanese patent application(s) are incorporated herein by reference:
       NO. 2015-036401 filed on Feb. 26, 2015.       
 
         [0005]    The contents of the following Japanese utility model application(s) are incorporated herein by reference:
       NO. 2015-003917 filed on Aug. 1, 2015.       
 
         [0007]    2. Related Art 
         [0008]    A camera installed in a mobile phone or the like is provided with a lens driving apparatus that drives an optical element such as a lens to be used for image-capturing for purposes of focusing or zooming. Many lens driving apparatuses comprise a bobbin that holds an optical element, a cover that houses the bobbin therein, and a drive unit that moves the bobbin in the optical axis-direction of the lens. 
         [0009]    When the bobbin is moved by the drive unit, a portion of the bobbin to which the drive unit is provided is moved by a predetermined distance. On the other hand, in some cases, the other portions are moved by distances that are not equal to the moving distance of the portion to which the drive unit is provided due to the gravitational force that acts in the opposite direction to the driving direction or the like, and the orientation of the bobbin inclines, which causes misalignment of the optical axis-direction of the lens. As a measure to solve this, a support unit that supports the bobbin to stabilize the orientation of the bobbin (the optical axis-direction of the lens) and guide the bobbin in the optical axis-direction is provided. 
         [0010]    As such a support unit, one in which grooves facing each other are provided to the bobbin and the cover, and a spherical ball is arranged therein has been widely used. This is for suppressing the influence of a frictional force generated in the support unit when moving the bobbin, by the ball rotating while being in contact with the bobbin and the cover. 
         [0011]    Conventionally, a drive unit is provided along one surface of a polygonal cylindrical bobbin having a rectangular section, and a support unit is provided along a surface facing the drive unit (please see Patent Literatures 1 and 2, for example). That is, the drive unit and the support unit are arranged in parallel. For this reason, for example, when the drive unit moves the bobbin upward, and the gravitational force that acts in the opposite direction to the moving direction acts on the support unit-side, it is difficult to move a surface of the bobbin to which the support unit is provided by a distance equal to the moving distance of a surface to which the drive unit is provided against the gravitational force, resulting in inclination of the bobbin relative to the cover, that is, to the optical axis. 
         [0012]    Also, in order to drive the bobbin smoothly in the optical axis-direction, it is preferable to increase the driving force for example by increasing the size of a drive magnet to increase the magnetic force of the drive magnet. 
         [0013]    However, for example if the magnetic force of the drive magnet is increased, the frictional force between a ball arranged between a bobbin and a cover, and the bobbin and the cover increases due to the magnetic attraction force between the drive magnet and the cover. For this reason, situations have occurred where the bobbin is not driven smoothly in the optical axis-direction even if the magnetic force of the drive magnet is increased. 
       PRIOR ART LITERATURES 
     Patent Literatures 
       [0000]    
       
         [Patent Literature 1] Japanese Patent Application Publication No. 2013-061666 
         [Patent Literature 2] Japanese Patent Application Publication No. 2015-007804 
       
     
         [0016]    An object of the present invention is to provide a lens driving apparatus that drives a lens in its optical axis-direction without inclining it, and a lens driving apparatus that drives a bobbin in the optical axis-direction smoothly without increasing the frictional force between a ball arranged between a bobbin and a cover, and the bobbin and cover while maintaining high driving power. 
       SUMMARY 
       [0017]    A lens driving apparatus according to an aspect of the present invention comprises:
       a polygonal cylindrical bobbin that houses a lens;   a box-shaped cover that receives the bobbin;   a drive unit that moves the bobbin in an optical axis-direction of the lens; and   a support unit that supports the bobbin and guides the bobbin in the optical axis-direction, wherein   the drive unit is configured with a coil and a drive magnet,   the coil is mounted on at least one inner surface of inner surfaces of the cover,   the drive magnet: is housed at a drive surface which is an outer surface of the bobbin and faces the coil; and has magnetic poles that are different at both sides in the optical axis-direction,   the support unit is configured with a plurality of first grooves, a plurality of second grooves and balls,   the plurality of first grooves are provided to at least two locations of an inner circumference of the cover, and extend in parallel with the optical axis-direction,   the plurality of second grooves are provided to at least two locations of a periphery of the bobbin, extend in parallel with the optical axis-direction of the lens, and face respective ones of the plurality of first grooves, the number of the plurality of second grooves being the same as the number of the plurality of first grooves; and   each of the balls is disposed between one of the plurality of first grooves and one of the plurality of second grooves facing the one of the plurality of first grooves, and   at least one of the plurality of second grooves is provided to a support surface that is not parallel with the drive surface, and is approximately parallel with a detection magnet mounted on the periphery of the bobbin.       
 
         [0030]    The second groove (a support unit) is provided to a support surface not parallel with the drive surface to which the drive unit is provided. Thereby, when a difference is generated between the moving distances of the drive surface and the surface facing it to cause inclination of the bobbin, the second groove provided to the bobbin inclines relative to the first groove provided to the cover. Due to the lengths of the first groove and second groove, separation between the positions of the two grooves that is generated due to the inclination becomes significant. This separation is prevented due to the ball within the grooves. That is, the bobbin never inclines. Note that the drive unit may be provided to not only one, but two or more surfaces. In this case, there are two or more drive surfaces, and there is a support surface that corresponds to and is not parallel with each of the drive surfaces. If the two or more drive surfaces are parallel with each other, there may only be one support surface not parallel with the drive surfaces. 
         [0031]    In the lens driving apparatus according to an aspect of the present invention, at least one of the plurality of second grooves provided to the support surface and the plurality of first grooves facing the plurality of second grooves has a V-shaped section. 
         [0032]    By having the V-shaped section, the groove width inside the groove becomes narrow. The ball is locked with the groove, and separation of the positions of the grooves can be surely prevented. Here, the “V-shape” means a shape whose groove width becomes narrower as the distance from the opening portion increases. The acute angle portion at the lower edge of the V-shape may be another shape. 
         [0033]    The lens driving apparatus according to an aspect of the present invention comprises a detecting unit that detects a position of the bobbin, wherein
       the detecting unit is configured with: a base plate on which a hole element to be mounted on one of the inner surfaces of the cover is installed; and the detection magnet mounted on a detection surface which is an outer surface of the bobbin and faces the base plate.       
 
         [0035]    The detecting unit is required for driving the lens. By providing the detection magnet here, when the bobbin is brought close to the magnetic body (iron) plate to be brought close to the cover, the ball disposed between the first groove and the second groove facing it is caused to be abutted on. 
         [0036]    Furthermore, because the magnetic force of the detection magnet can be adjusted to be small while maintaining the high driving power by making the detection magnet and the drive magnet separate bodies, the frictional force can be reduced by adjusting the contact pressure between the ball arranged between the bobbin and the cover, and the bobbin and cover. 
         [0037]    In the lens driving apparatus according to an aspect of the present invention, the detection magnet is provided at a position that allows the cover and the bobbin to be brought close to each other and allows the balls disposed between the plurality of first grooves and the plurality of second grooves facing the plurality of first grooves to abut on the plurality of first grooves and the plurality of second grooves. 
         [0038]    The bobbin and the cover are brought close to each other on the support surface. The bobbin can be supported, and guided in the optical axis-direction by causing the ball to engage with the groove at a smaller inclination. 
         [0039]    In the lens driving apparatus according to an aspect of the present invention, one of the plurality of second grooves is disposed at a portion of the detection surface, the portion corresponding to each of both sides of the base plate. 
         [0040]    The bobbin is supported at both sides of the detection surface. Inclination of the bobbin relative to the detection surface can be surely prevented. In particular, this is effective when the detection surface is orthogonal to the drive surface. 
         [0041]    With a lens driving apparatus according to one aspect of the present invention, it becomes possible to drive a lens without inclining it and smoothly in the optical axis-direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0042]      FIGS. 1A and 1B  are exploded perspective views that show the configuration of a lens driving apparatus. 
           [0043]      FIGS. 2A and 2B  are exploded perspective views that show the configuration of the lens driving apparatus. 
           [0044]      FIG. 3  is a cross-sectional view that shows the configuration of the lens driving apparatus. 
           [0045]      FIGS. 4A and 4B  are figures for explaining actions of a support unit. 
           [0046]      FIGS. 5A and 5B  are figures for explaining actions of the support unit. 
           [0047]      FIGS. 6A, 6B and 6C  are figures for explaining actions of the support unit. 
           [0048]      FIG. 7  is a cross-sectional view for explaining details of the support unit. 
           [0049]      FIG. 8  is a figure that shows an example of the lens driving apparatus. 
           [0050]      FIG. 9  is a figure that shows an example of the lens driving apparatus. 
           [0051]      FIGS. 10A and 10B  are exploded perspective views that show the configuration of the lens driving apparatus. 
           [0052]      FIGS. 11A and 11B  are figures that show a ball locking tool. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0053]    Hereinafter, (some) embodiment(s) of the present invention will be described. 
       First Embodiment 
       [0054]      FIGS. 1A and 1B  are exploded perspective views that show the configuration of a lens driving apparatus. The lens driving apparatus is configured with a cover  1 , a bobbin  2 , a plate  6  and a base  7 , and comprises a drive unit  3 , a support unit  4  and a detecting unit  5 .  FIG. 1A  shows the cover  1  and the plate  6 , and  FIG. 1B  shows the bobbin  2  and the base  7 . Balls  43  to be inserted between the cover  1  and the bobbin  2  are shown in both  FIG. 1A  and  FIG. 1B  to indicate the relationship between  FIG. 1A  and  FIG. 1B . 
         [0055]    The bobbin  2  comprises a lens holding unit  21  that holds a lens (not illustrated), and moves within the cover  1  in the optical axis-direction of the lens (the vertical direction on the sheet of paper). In one example, the bobbin  2  is formed into a polygonal cylindrical shape having a square top surface by using resin. 
         [0056]    The drive unit  3  is configured with a coil  31  attached to the cover  1  and a drive magnet  32  attached to the bobbin  2 . The drive magnet  32  has magnetic poles that are different in the optical axis-direction of the lens (the up-down directions in the figure). An upward electromagnetic force can be provided to the bobbin  2  by a current flowing through the coil  31 , and a downward electromagnetic force can be provided to the bobbin  2  by a reverse current. 
         [0057]    That is, the bobbin  2  can be driven to be at any position in the up-down directions by controlling a current flowing through the coil  31 . 
         [0058]    The support unit  4  is configured with two first grooves  41  provided to the cover  1 , two second grooves  42  provided to the bobbin  2 , and three balls  43  disposed between the first grooves  41  and the second grooves  42 . Although the first grooves  41  are not shown in  FIGS. 1A and 1B , the first groove  41  is shown in  FIG. 2A  that is an exploded perspective view seen from the opposite side of  FIGS. 1A and 1B . Although only one first groove  41  is shown in  FIG. 2A , another one first groove  41  is provided to a rear portion of the cover  1  main body that is symmetrical about the left-right directions. The two first grooves  41  and the two second grooves  42  face each other. Note that the number of the balls  43  may not be three, but two, or four or larger. The numbers of the first grooves  41  and second grooves  42  may not be two, but three or larger, but is preferably two for attaining stable support. 
         [0059]    The bobbin  2  is pressed against and supported by the cover  1  via the balls  43 . Because the balls  43  contact the first grooves  41  and the second grooves  42  and roll, the bobbin  2  moves in the optical axis-direction (the up-down directions in the figure) without much resistance. 
         [0060]    The detecting unit  5  is configured with a hole element  51 , a base plate  52  for mounting the hole element  51  on the cover  1 , and a detection magnet  53  to be mounted on the bobbin  2 . The hole element  51  detects the magnetic field of the detection magnet  53 , and detects the position of the bobbin  2  (relative position to the cover  1 ). 
         [0061]    When the position of the bobbin  2  detected by the detecting unit  5  and a desired arrangement position of the bobbin  2  do not match, current is caused to flow through the coil  31 , and the bobbin  2  can be moved by the drive unit  3 . 
         [0062]      FIG. 3  is a cross-sectional view that shows the configuration of the lens driving apparatus. While exploded perspective views are shown in  FIGS. 1A, 1B, 2A and 2B ,  FIG. 3  shows the lens driving apparatus with its configuration not decomposed. 
         [0063]    The drive unit  3  (the coil  31  and the drive magnet  32 ) is provided to one side of a rectangle of the cover  1  and bobbin  2  that have rectangular sections. The support unit  4  (the first grooves  41 , the second grooves  42  and the balls  43 ) and the detecting unit  5  (the hole element  51 , the base plate  52  and the detection magnet  53 ) are provided to another side orthogonal to the one side to which the drive unit  3  is provided. Note that the one side to which the drive unit  3  is provided and the other side to which the support unit  4  and the detecting unit  5  are provided may not be orthogonal to each other, but only have to be not parallel (the reason for this is explained later). 
         [0064]    The drive unit  3  is provided only to one side of the rectangle. Here, there is an issue: when the bobbin  2  is to be moved by the drive unit  3 , how the surfaces of the bobbin  2  facing the other three sides (without the drive unit  3 ) can be moved by the distance equal to the moving distance of the surface to which the drive unit is provided. When the moving distances are not equal, the bobbin  2  inclines relative to the cover  1 , i.e., to the optical axis, and the optical axis of a lens inclines accordingly. 
         [0065]      FIGS. 4A and 4B  are figures for explaining actions of the support unit.  FIGS. 4A and 4B  correspond to conventional techniques. The support unit  4  that is, in  FIG. 3 , provided to another side orthogonal to one side to which the drive unit  3  is provided is provided to the same side as the drive unit  3  (see  FIG. 4A ). 
         [0066]      FIG. 4B  shows a section taken through the line B-B in  FIG. 4A . The bobbin  2  is moved upward in the figure by the drive unit  3 . It is assumed that the gravitational force that acts in the downward direction in the figure is acting on the bobbin  2 . 
         [0067]    Depending on the machining accuracy of the first grooves  41  and second grooves  42 , gaps may be formed between respective ones of the first grooves  41  and second grooves  42 , and the balls  43 . Also, the cover  1  and the bobbin  2  may be separated. For this reason, as shown in  FIG. 4B , the bobbin  2  may incline relative to the cover  1 , that is, to the optical axis. 
         [0068]    So far, an example in which the support unit  4  is provided to the same side as the drive unit  3  has been explained. Inclination of the bobbin  2  relative to the cover  1 , that is, to the optical axis as shown in  FIG. 4B  happens similarly in a case where the support unit  4  is not provided to the same side as the drive unit  3 , but to a side parallel with the side to which the drive unit  3  is provided. 
         [0069]      FIGS. 5A and 5B  are figures for explaining actions of the support unit.  FIGS. 5A and 5B  correspond to conventional techniques like  FIGS. 4A and 4B  (see Patent Literature 2). The support unit  4  is provided to a parallel side facing the drive unit  3 . 
         [0070]    As shown in  FIG. 5B , like  FIG. 4B , the bobbin  2  inclines relative to the cover  1 , that is, to the optical axis. 
         [0071]      FIGS. 6A, 6B and 6C  are figures for explaining actions of the support unit.  FIGS. 6A, 6B and 6C  relate to the present embodiment, and  FIG. 6A  corresponds to the one shown in  FIG. 3 . The support unit  4  is provided to another side orthogonal to the side to which the drive unit  3  is provided. 
         [0072]      FIG. 6B  shows a section taken through the line B-B in  FIG. 6A . The bobbin  2  is moved upward in the figure by the drive unit  3 . It is assumed that the gravitational force that acts in the downward direction in the figure is acting on the bobbin  2 . 
         [0073]    The following description explains that generation of gaps between respective ones of the first grooves  41  and second grooves  42 , and the balls  43 , and separation between the cover  1  and the bobbin  2  are prevented, and the bobbin  2  never inclines relative to the cover  1 , that is, to the optical axis. 
         [0074]    Because, in the figure, the electromagnetic force to drive the bobbin  2  upward acts on the left side, and the gravitational force to drive the bobbin  2  downward acts on the (entire) right side, the bobbin  2 , when it inclines relative to the cover  1 , rotates clockwise in the figure. In  FIGS. 4A and 4B , such rotation can occur because of generation of gaps between respective ones of the first grooves  41  and second grooves  42 , and the balls  43 , and separation between the cover  1  and the bobbin  2 . However, in  FIGS. 6A, 6B and 6C , such rotation causes misalignment in the facing relationship between the first grooves  41  and the second grooves  42  as shown in  FIG. 6C . The first grooves  41  (solid lines in the figure) provided to the cover  1  are immovable, and the second grooves  42  provided to the bobbin  2  incline (broken lines in the figure). The balls  43  prevent inclination like the one shown in  FIG. 6C . 
         [0075]    So far, an example in which the side to which the drive unit  3  is provided and the other side to which the support unit  4  is provided are orthogonal to each other has been explained. Even when they are not orthogonal, as long as the side to which the drive unit  3  is provided and the other side to which the support unit  4  is provided are not parallel, misalignment in the facing relationship between the first grooves  41  and the second grooves  42  as shown in  FIG. 6C  is prevented. As long as they are not parallel, they do not have to be orthogonal. Because when they are orthogonal, inclination of the bobbin  2  can be most efficiently prevented, they are preferably orthogonal. 
         [0076]      FIG. 7  is a cross-sectional view for explaining details of the support unit. The first grooves  41  and the second grooves  42  have V-shapes whose width decreases as the depth from the opening portions at which the first grooves  41  and the second grooves  42  face each other increases (the V-shapes excluding acute angle portions at their lower edges). The balls  43  contact the first grooves  41  and the second grooves  42  at two points, respectively. The first grooves  41  and the second grooves  42  are never misaligned in the direction of the while arrow in the figure, and inclination of the bobbin  2  is prevented. 
         [0077]    The support unit  4  is provided to the same side as the detecting unit  5 . Thereby, the plate  6  (or the base plate  52 ) formed with a magnetic body (iron) is attracted also to the cover  1  because of the plate  6  being attracted to the bobbin  2  due to the detection magnet  53 . Separation between the cover  1  and the bobbin  2  is prevented, and it can be ensured that the balls  43  contact the first grooves  41  and the second grooves  42  at two points, respectively. Note that misalignment in the direction of the black arrow in  FIG. 7  can also be prevented. Inclination of the bobbin  2  in a case where the electromagnetic force of the drive unit  3  is uneven due to the influence of the gravitational force and the frictional resistance between the balls  43 , and the first grooves  41  and second grooves  42  in  FIG. 6A  is prevented. 
         [0078]    By providing at least one of the second grooves  42  to a side not parallel with the side to which the drive unit  3  is provided, inclination of the bobbin  2  is prevented. Such an example is shown below. 
         [0079]      FIG. 8  is a figure that shows an example of the lens driving apparatus. Two second grooves  42  are provided to different sides. The two sides to which the second grooves  42  are provided are both orthogonal to the side to which the drive unit  3  is provided. As in the one shown in  FIGS. 6A, 6B and 6C , because misalignment in the facing relationship between the first grooves  41  and the second grooves  42  does not occur, the bobbin  2  never inclines. 
         [0080]      FIG. 9  is a figure that shows an example of the lens driving apparatus. The support unit  4  is provided at the position which is the same as that shown in  FIGS. 6A, 6B and 6C . A difference from the one shown in  FIGS. 6A, 6B and 6C  is that two drive units  3  (two sets ( 31   a  and  31   b , and  32   a  and  32   b ) of the coil  31  and drive magnet  32 ) are provided to facing sides. 
         [0081]    Because the bobbin  2  is driven by the two drive units  3 , a situation never occurs where a side facing the drive unit  3  does not move (or moves slowly) due to the influence of the gravitational force, which occurs when only a single drive unit  3  is provided. In combination with the effect of the support unit  4 , inclination of the bobbin  2  can surely be prevented. 
         [0082]    As explained in detail above, the lens driving apparatus  1  according to the present embodiment can drive the bobbin  2  in the optical axis-direction without inclining it. 
       Second Embodiment 
       [0083]    The present embodiment has a structure different from that in the first embodiment. Bobbin inclination prevention by the first grooves  41 , the second grooves  42  and the balls  43 , and mechanisms of the bobbin  2 , the drive unit  3  and the detecting unit  5  are the same as those in the first embodiment, and explanation thereof is omitted. 
         [0084]      FIGS. 10A and 10B  are exploded perspective views that show the configuration of the lens driving apparatus. The lens driving apparatus is configured with the cover  1 , the bobbin  2 , the plate  6  and a top cover  71 , and comprises the drive unit  3 , the support unit  4  and the detecting unit  5 .  FIG. 10A  shows the bobbin  2  and the top cover  71 , and  FIG. 10B  shows the cover  1  and the plate  6 . The balls  43  to be inserted between the cover  1  and the bobbin  2  are shown in both  FIG. 10A  and  FIG. 10B  to indicate the relationship between  FIG. 10A  and  FIG. 10B . 
         [0085]    In contrast to the one according to the first embodiment (see  FIGS. 1A and 1B ), the cover  1  is disposed at a lower portion. Strictly speaking, one that is formed by integrating the base  7  and the cover  1  in the first embodiment corresponds to the cover  1  of the present embodiment, and the top cover  71  to cover an upper portion is added. 
         [0086]    Two drive units  3  (the coils  31  and the drive magnets  32 ) are provided to facing sides. Thereby, the gravitational force that acts on a side facing the drive unit  3  can be ignored, and inclination of the bobbin  2  decreases. 
         [0087]    The detecting unit  5  (the hole element  51 , the base plate  52  and the detection magnet  53 ) are provided to a side to which the drive unit  3  is not provided. 
         [0088]    The support unit  4  is configured with two first grooves  41  provided to the cover  1 , two second grooves  42  provided to the bobbin  2 , and three balls  43  disposed between the first grooves  41  and the second grooves  42 . Two support units  4  (one formed with a first groove  41   a  and a second groove  42   a , and another with a first groove  41   b  and a second groove  42   b ) are provided. Hereinafter, the one formed with the first groove  41   a  and the second groove  42   a  is referred to as a support unit  4   a  and the one formed with the first groove  41   b  and the second groove  42   b  is referred to as a support unit  4   b.    
         [0089]    The support units  4   a  and  4   b  are provided to the same surface as the detecting unit  5 . 
         [0090]    Bobbin inclination prevention is ensured by bringing the cover  1  and the bobbin  2  close to each other by the detection magnet  53 . Also, bobbin inclination prevention is further ensured by providing the detection magnet  53  to a surface not parallel with the surfaces to which the two drive units  3  are provided. 
         [0091]      FIGS. 11A and 11B  are figures that show a ball locking tool. The figures show sections of portions to which the support units  4   a  and  4   b  are provided. The ball locking tool  44  (protrusion) is provided above the balls  43  in the top cover  71 , and stabilizes the balls  43  between the cover  1  and the bobbin  2 . 
         [0092]    Note that as the ball locking tool  44 , a resin member or the like may be used in place of the protrusion of the top cover  71 . 
       INDUSTRIAL APPLICABILITY 
       [0093]    The lens driving apparatus according to one aspect of the present invention is suited to driving a lens in its optical axis-direction without inclining it. 
       EXPLANATION OF REFERENCE SYMBOLS 
       [0000]    
       
         
           
               1 : cover 
               2 : bobbin 
               21 : lens holding unit 
               3 : drive unit 
               31 : coil 
               32 : drive magnet 
               4 : support unit 
               41 : first groove 
               42 : second groove 
               43 : ball 
               44 : ball locking tool 
               5 : detecting unit 
               51 : hole element 
               52 : base plate 
               53 : detection magnet 
               6 : plate 
               7 : base 
               71 : top cover