Abstract:
There is disclosed a lens frame structure having a movable lens holding frame, a shaft which guides movement of the lens holding frame and a support member which supports the shaft. Owing to an impact force applied to a lens frame, the lens holding frame and the support member are able to relatively move in an axial direction of the shaft to come in face contact with each other. At least a part of regions of the lens holding frame and the support member which come in face contact with each other are slant surfaces with respect to the shaft. 
     Otherwise, the regions of the lens holding frame and the support member which come in face contact with each other can be a pair of a concave surfaces and a convex surface (a wedge surface, a curved surface, a conical surface or the like) substantially parallel to each other.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2006-205144 filed on Jul. 27, 2006, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a lens frame structure which moves a lens frame forwards and backwards. 
         [0004]    2. Description of the Related Art 
         [0005]    In a lens barrel in which a lens frame capable of moving forwards and backwards is incorporated, it is demanded that, even if impact is applied to a camera owing to drop or the like, the incorporated lens frame should move so that a lens is protected from breakage. 
         [0006]    An actuator unit disclosed in Japanese Patent Application Laid-Open No. 2005-292514 is a unit which is applicable to an optical device of a small-sized camera. This actuator unit has a lens frame structure which moves the lens frame forwards and backwards along a guide shaft. In a case where an impact force is applied to this actuator unit in an optical axis direction, the lens frame moves in the optical axis direction and abuts on a comparatively large abutment surface crossing an optical axis at right angles to suppress concentration of stress at contact, so that the breakage of a lens is prevented. 
         [0007]    On the other hand, another conventional lens barrel has a lens barrel structure shown in an enlarged view of a main part in  FIG. 12 . This lens barrel  100  has a barrel main body  101 , a guide shaft  102  fixed to the barrel main body  101  in parallel with a lens optical axis O, and a lens frame  103  supported by the guide shaft  102 . The lens frame  103  is formed into an L-shape, and has a guide portion  103   a  fitted into the guide shaft  102  and a lens holding portion  103   b  which holds a lens  104 . 
         [0008]    In a case where the conventional lens barrel  100  shown in  FIG. 12  receives an impact force and the lens frame  103  drops down along the guide shaft  102  in an SO direction, as shown in a collision state diagram of  FIG. 13 , either of the guide portion  103   a  and the lens holding portion  103   b  collides with an abutment surface  101   a  or  101   b  crossing the optical axis O at right angles. Even after the collision, as shown in a repulsive state diagram of  FIG. 14 , the portion is repulsed from the abutment surface  101   a,    101   b  owing to repulsion to move in an S 1  direction. 
       SUMMARY OF THE INVENTION 
       [0009]    A lens frame structure of the present invention has a movable lens holding frame, a shaft which guides movement of the lens holding frame and a support member which supports the shaft. Owing to an impact force applied to a lens frame, the lens holding frame and the support member relatively move in an axial direction of the shaft to come into face contact with each other. At least a part of regions of the lens holding frame and the support member which come into face contact with each other are slant surfaces with respect to the shaft. 
         [0010]    For example, the regions of the lens holding frame and the support member which come into face contact with each other are all flat surfaces that are substantially parallel to each other and that slant with respect to the shaft. Alternatively, the regions of the lens holding frame and the support member which come into face contact with each other may be a concave surface and a convex surface (a wedge surface, a curved surface, a conical surface or the like) which are substantially parallel to each other. 
         [0011]    One example of a constitution of the present invention can be represented as follows. A lens frame structure comprising: a shaft member along which a lens holding frame moves; the lens holding frame having a holding frame portion which holds a lens and a shaft fitting portion which is integrally formed with this holding frame portion and which fits into the shaft member to slide along the shaft member, a shaft end surface of the shaft fitting portion including a slant surface with respect to the center axis of the shaft member; and a shaft support member which supports the shaft member and which includes an abutment surface to come into face contact with the shaft end surface of the lens holding frame and abut on the shaft end surface. 
     
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0012]    These and other features, aspects, and advantages of the apparatus and methods of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where: 
           [0013]      FIG. 1  is a perspective view of a lens barrel device to which a lens frame structure according to one embodiment of the present invention is applied; 
           [0014]      FIG. 2  is a back view of the lens barrel device of  FIG. 1 ; 
           [0015]      FIG. 3  is a perspective view of a lens frame unit constituting the lens barrel device of  FIG. 1 ; 
           [0016]      FIG. 4  is a back view of the lens frame unit of  FIG. 3 ; 
           [0017]      FIG. 5  shows a state of a second lens frame of the lens frame unit immediately before a camera in which the lens barrel device of  FIG. 1  is incorporated drops down; 
           [0018]      FIG. 6  shows a state in which the camera drops down from the state of  FIG. 5  and the second lens frame collides with a first lens frame; 
           [0019]      FIG. 7  shows a state of the second lens frame immediately before the camera drops down in a case where a modification of the second lens frame of the lens barrel device of  FIG. 1  is applied; 
           [0020]      FIG. 8  shows a state in which the camera drops down from the state of  FIG. 7  and the second lens frame of the modification collides with a first lens frame; 
           [0021]      FIG. 9  is a diagram showing a state of a lens frame of a lens barrel device of a second embodiment before a camera drops down; 
           [0022]      FIG. 10  is a diagram showing a state of a lens frame of a lens barrel device of a third embodiment before a camera drops down; 
           [0023]      FIG. 11  is a diagram showing a state of a lens frame of a lens barrel device of a fourth embodiment before a camera drops down; 
           [0024]      FIG. 12  is a sectional view of a main part of a conventional lens barrel; 
           [0025]      FIG. 13  is a diagram of a collision state of the lens barrel of  FIG. 12 ; and 
           [0026]      FIG. 14  is a diagram of a repulsive state after collision of the lens barrel of  FIG. 12 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    Preferred embodiments of the invention are described below with reference to the accompanying drawings. 
         [0028]      FIG. 1  is a perspective view of a lens barrel device to which a lens frame structure according to one embodiment of the present invention is applied.  FIG. 2  is a back view of the lens barrel device.  FIG. 3  is a perspective view of a lens frame unit constituting the lens barrel device.  FIG. 4  is a back view of the lens frame unit.  FIGS. 5 ,  6  show a behavior of a second lens frame of the lens frame unit in a case where a camera in which the lens barrel device is incorporated drops down,  FIG. 5  shows a state immediately before the camera drops down, and  FIG. 6  shows a state in which the camera drops down and the second lens frame collides with a first lens frame. 
         [0029]    As shown in  FIG. 1 , a lens barrel device  1  to which a lens frame structure of the present embodiment is applied has a fixed frame  2  having a box-like shape, a first lens frame  3 , a second lens frame  4  of a lens holding frame disposed along an optical axis O 2  (described later) under the first lens frame  3 , a shutter frame  5 , a third lens frame  6  and a fourth lens frame  7 . Furthermore, the lens barrel device  1  has the guide shafts  8 ,  9  which are shaft members supported by the fixed frame  2  and the first lens frame  3  in parallel with the optical axis O 2 , a lead screw  10 , a zoom cam  11 , a shutter driving motor  14 , a focusing motor  15  and a zooming motor  16 . 
         [0030]    The first lens frame  3  is secured and attached to an upper portion of the fixed frame  2 , and contains a first lens (not shown) having an optical axis O 1  and a mirror (not shown) for bending the optical axis O 1  by 90° toward the optical axis O 2 . Beside the first lens frame, a shaft support portion  21  is fixed as a shaft support member which supports a guide shaft  9 . A protruding undersurface of this shaft support portion  21  (on the side of the second lens frame  4 ) is provided with a slant surface  21   a  as a flat surface which slants with respect to the direction of the guide shaft  9  direction ( FIG. 5 ). An externally extending normal of the slant surface  21   a  tilts away from the center axis of the guide shaft  9 . 
         [0031]    The second lens frame  4  has a holding frame portion  4   a  which holds a second lens  32  and which is made of a synthetic resin, and a sleeve  22  made of a metal. The sleeve  22  made of the metal is a member which is fitted into a fitting hole  4   b  of the holding frame portion  4   a  and fixed with adhesive, and is a shaft fitting portion through which the guide shaft  9  slidably extends. The holding frame portion  4   a  is provided with a cutout-like guide groove  4   c  (not shown) on the side opposite to the fitting hole  4   b.  On the side provided with the fitting hole  4   b  of the holding frame portion  4   a,  a spring hook  4   d  is disposed at which a tension spring  13  is hooked. The guide groove  4   c  is slidably fitted into a guide protrusion (not shown) provided at the fixed frame  2 . The second lens frame  4  is urged by the tension spring  13  in such a direction that the second lens frame  4  comes close to the third lens frame  6 . In this state, the second lens frame  4  is slidably supported by the guide shaft  9  while rotation of the second lens frame  4  is regulated by the guide protrusion of the fixed frame  2 . 
         [0032]    A tip end surface of the sleeve  22  on a shaft end side is provided with a slant surface  22   a  as a flat surface which slants with respect to the guide shaft  9  direction (i.e., a direction parallel to the optical axis O 2 ) ( FIG. 5 ). The externally extending normal of the slant surface  22   a  tilts away from the center axis of the guide shaft  9 , and this slant surface is a surface parallel to the slant surface  21   a  of the shaft support portion  21 . Therefore, in a case where the second lens frame  4  receives an external force to move until the frame abuts on the shaft support portion  21 , the slant surface  22   a  comes into face contact with the slant surface  21   a.    
         [0033]    The shutter frame  5  is secured to and supported by the fixed frame  2 , and an openable/closable shutter plate is stored in the shutter frame. The shutter plate is driven by the shutter driving motor  14  to open or close. 
         [0034]    The third lens frame  6  is a holding frame which holds a third lens  33  and which is made of a synthetic resin. The third lens frame  6  is slidably supported by the guide shaft  9  in an optical axis O 2  direction in a state in which rotation of the frame is regulated by the guide shaft  8 . 
         [0035]    The fourth lens frame  7  is a holding frame which holds a fourth lens  34  and which is made of a synthetic resin. The fourth lens frame  7  is disposed in front of a CCD (not shown) disposed under the lens barrel device  1 . This fourth lens frame  7  is slidably supported by the guide shaft  8  in the optical axis O 2  direction in a state in which rotation of the frame is regulated by the guide shaft  9 . The fourth lens frame  7  is held so as to abut on a nut member into which the lead screw  10  is screwed by an urging force of a tension spring  12 . 
         [0036]    The zoom cam  11  has a cylindrical end surface cam portion  11   a  formed at an upper end portion and a cylindrical groove cam portion  11   b  provided at the center portion. A cam abutment portion (not shown) of the second lens frame  4  receives the urging force of the tension spring  13  to abut on the cylindrical end surface cam portion  11   a  from the side of the upper end. A driven pin portion (not shown) of the third lens frame  6  is slidably fitted into the cylindrical groove cam portion  11   b.    
         [0037]    During zooming, when the zoom cam  11  rotates, the second lens frame  4  is driven to move forwards and backwards in the optical axis O 2  direction via the cylindrical end surface cam portion  11   a.  The third lens frame  6  is simultaneously moved forwards and backwards in the optical axis O 2  direction by the cylindrical groove cam portion  11   b.    
         [0038]    On the other hand, during focusing, the fourth lens frame  7  is driven forwards and backwards via the lead screw  10  rotated by the focusing motor  15  to move in the optical axis O 2  direction. 
         [0039]    The lens barrel device  1  constituted as described above is incorporated in a camera in a state in which the device is fixed to an outer cover of the camera. When the camera drops down, each constituting member of the lens barrel device  1  receives an impact force. Especially, in a case where the camera drops down upside down (drops down in an S 0  direction of  FIGS. 1 ,  2 ) and the impact force is not less than a predetermined level, the second lens frame  4  comes away from the cylindrical end surface cam portion  11   a  of the zoom cam  11  against the urging force of the tension spring  13 , and the slant surface  22   a  of the sleeve  22  collides with the slant surface  21   a  of the shaft support portion  21  on a first lens frame  3  side, and receives the impact force ( FIG. 6 ). 
         [0040]    However, since the slant surface  22   a  of the second lens frame  4  collides with the slant surface  21   a  to receive the impact force as described above, an abutment surface pressure decreases as compared with a case where vertical surfaces abut on each other. Since a force is generated in a direction of the normal of the slant surfaces, the guide shaft  9  slightly bends, and the second lens frame  4  slightly moves along the slant surface owing to a fitting gap between the second lens frame  4  and the guide shaft  9 . Because of these movements, the impact force is absorbed. Moreover, bounce of the second lens frame  4  after the collision is reduced. These phenomena have been clarified also by simulations. 
         [0041]    Therefore, a stress due to impact generated at upper and lower bonded portions P 2 , P 1  between the holding frame portion  4   a  of the second lens frame  4  and the sleeve  22  is suppressed to prevent damage and deformation of the portions. 
         [0042]    As described above, according to the lens barrel device  1  of the first embodiment, in a case where the impact force is received, even if the second lens frame  4  moving along the guide shaft  9  receives the impact at the end portion (the shaft support portion  21 ) of the guide shaft  9 , the slant surfaces ( 22   a,    21   a ) abut on each other at the end portion of the guide shaft  9 . In consequence, the impact force is absorbed. This constitution is effective in preventing damages of the bonded portions between the lens holding portion of the second lens frame  4  and the sleeve portion. 
         [0043]    It is to be noted that the first embodiment is assumed to have a structure in which, in a case where the second lens frame  4  receives the impact in the S 0  direction as shown in  FIG. 5 , the second lens frame abuts on the only sleeve  22 . However, the present invention is not limited to this structure. Even when a tip end portion  4 e of the lens holding portion  4   a  of the second lens frame  4  and an end surface of the first lens frame  3  are slant surfaces and the slant surfaces are allowed to abut on each other during collision, a similar effect can be produced. Even in such a structure, it is considered that, owing to fluctuations of member dimensions, rattle and the like, the slant surface  22   a  may abut on the slant surface  21   a  before the tip end portion  4   e  abuts on the end surface. Therefore, when the impact force is exerted, the impact force can similarly be absorbed by one or both of sets of the slant surfaces. 
         [0044]    Moreover, in the first embodiment, the sleeve  22  provided at the second lens frame  4  is a separate member made of a metal. However, the present invention is not limited to this embodiment. Even in a case where a sleeve is integrally molded with the holding frame portion  4   a,  when an end portion is provided with a similar slant surface, a similar effect can be produced. 
         [0045]    Furthermore, slant directions of the slant surfaces  22   a  and  21   a  are not limited to those of the first embodiment described above, and slant surfaces slanted in different directions in accordance with a shape of the second lens frame may be adopted so as to obtain a further effect. 
         [0046]    In addition, as shown in  FIG. 7 , a modification may be proposed in which, instead of disposing the slant surface at a sleeve  22 A provided at a second lens frame  4 A, a tip end portion of a lens holding portion  4 Aa is provided with a slant surface  4 Ae, and a slant surface  3 Ae capable of abutting on the slant surface  4 Ae is disposed on the side of a first lens frame  3 A. In this modification, when impact is received in an S 0  direction, the second lens frame  4 A moves in the S 0  direction, and the slant surface  4 Ae abuts on the slant surface  3 Ae as shown in  FIG. 8 . Even in this modification, since the slant surfaces abut on each other, an impact force is absorbed in the same manner as in the above embodiment, a stress due to the impact generated at bonded portions P 3 , P 4  of the lens holding portion  4 Aa is suppressed, and damage and deformation of the portion are prevented. This art shown in  FIG. 7  may be used together with the above art shown in  FIG. 5 . 
         [0047]    Next, a second embodiment of the present invention will be described. Since a large part of the second embodiment is the same as that of first embodiment, only respects different from the first embodiment will be described below. 
         [0048]      FIG. 9  is a diagram corresponding to  FIG. 5  of the first embodiment. As shown in  FIG. 9 , the slant surface  22   a  of the first embodiment is formed into a V-shaped wedge shape in the second embodiment. A tip end of the slant surface has an abutment surface  22   a - 1  having a wedge angle O 2 . Moreover, the slant surface  21   a  of the first embodiment turns to an abutment surface  21   a - 1  as a concave surface of the V-shape having an open angle θ 1  in the second embodiment. In this case, θ 2 &gt;θ 1  is set. That is, the tip end angle θ 2  of a wedge on a convex side is set to be larger than the tip end angle θ 1  of a wedge receiving concave side. 
         [0049]    In consequence, when impact is applied to a lens frame, the abutment surface  22   a - 1  having the wedge shape bites into a V-shape while opening the angle θ 1  of the partner abutment surface  21   a - 1 , and an impact force is absorbed. 
         [0050]    Moreover, even when the abutment surface having the wedge shape is constituted on the side of a fixed frame and the abutment surface as an upper concave surface of the V-shape is constituted on the side of a lens frame, a similar effect is obtained. 
         [0051]    Next, a third embodiment of the present invention will be described. Since a large part of the third embodiment is the same as that of first embodiment, only respects different from the first embodiment will be described below. 
         [0052]      FIG. 10  is a diagram corresponding to  FIG. 5  of the first embodiment. As shown in  FIG. 10 , the slant surface  22   a  of the first embodiment is replaced with a concave abutment surface  22   a - 2  formed into a spherical surface or an R-surface having a curvature in the third embodiment. The slant surface  21   a  of the first embodiment turns to a convex abutment surface  21   a - 2  formed into a spherical surface or an R-surface having a curvature in the third embodiment. In this case, a relation between a radius R 1  of curvature of the abutment surface  21   a - 2  and a radius R 2  of curvature of the abutment surface  22   a - 2  is set to R 2 &lt;R 1 . That is, the radius R 1  of curvature of the curved surface on a convex side is set to be larger than the radius R 2  of curvature on a concave side. 
         [0053]    In consequence, in a case where impact is applied to a lens frame, while the abutment surface  22   a - 2  having the radius R 2  abuts on the partner abutment surface  21   a - 2  to reduce the curvature thereof, the surface is deformed to absorb an impact force. 
         [0054]    Moreover, the concave abutment surface may be formed on a fixed frame side, and the convex abutment surface may be formed on a lens frame side. At this time, a relation between a radius R 1 ′ of curvature of the concave abutment surface and a radius R 2 ′ of curvature of the convex abutment surface is set to R 2 ′&gt;R 1 ′. 
         [0055]    Next, a fourth embodiment of the present invention will be described. Since a large part of the fourth embodiment is the same as that of first embodiment, only respects different from the first embodiment will be described below. 
         [0056]      FIG. 11  is a diagram corresponding to  FIG. 5  of the first embodiment. As shown in  FIG. 11 , the slant surface  22   a  of the first embodiment is replaced with a convex conical abutment surface  22   a - 3  in the fourth embodiment. The slant surface  21   a  of the first embodiment turns to a conical abutment surface  21   a - 3  in the third embodiment. Here, an open angle θ 3  of the convex conical abutment surface  22   a - 3  is larger than an open angle θ 4  of the concave conical abutment surface  21   a - 3 . Functions of these abutment surfaces are similar to those of the second and third embodiments. 
         [0057]    The lens frame structure according to the present invention is effective in efficiently absorbing an impact force owing to drop or the like with a simple constitution to prevent damage of a lens frame. 
         [0058]    While there has been shown and described what are considered to be preferred embodiments of the invention, it will, of course, be understood that various modifications and changes in form or detail could readily be made without departing from the spirit of the invention. It is therefore intended that the invention not be limited to the exact forms described and illustrated, but constructed to cover all modifications that may fall within the scope of the appended claims.