Patent Publication Number: US-8540439-B2

Title: Blade drive device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of and claims priority to International Patent Application No. PCT/JP2008/062859 filed on Jul. 16, 2008, which claims priority to Japanese Patent Application No. 2007-233367 filed on Sep. 7, 2007, subject matter of these patent documents is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to blade drive devices. 
     2. Description of the Related Art 
     Generally, a blade drive device for a camera includes: a board having an opening; a blade opening and closing the opening; and a drive source, such as an actuator, driving the blade (see Japanese Unexamined Patent Application Publication No. 2006-11293). In such a blade drive device, a high-power actuator is employed, so that a shutter speed can be increased. 
     However, the high-power actuator has a large size. Thus, there is a problem that the size of the blade drive device is also increased by employing such an actuator. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a blade drive device which is reduced in size and has an improved shatter speed. 
     According to an aspect of the present invention, there is provided a blade drive device including: a blade; a drive source that drives the blade; and a chassis that has an opening opened and closed by the blade and that houses the blade and the drive source, the drive source including: a rotor that is rotatably supported; a stator around which a coil for excitation is wound and which applies a rotational force to the rotor, and the stator being arranged to surround a periphery of the opening and having a rectangular shape. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of a configuration of a blade drive device according to a first embodiment; 
         FIG. 2  is a cross-sectional view taken along a line A-A in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view taken along a line B-B in  FIG. 1 ; 
         FIG. 4  is a rear view of a blade drive device according to the first embodiment; 
         FIG. 5  is an enlarged view of a connecting portion of iron pieces, as illustrated in  FIG. 2 ; 
         FIG. 6  is a cross-sectional view of a filling portion; 
         FIG. 7  is an exemplary cross-sectional view of a snap fitting structure; 
         FIG. 8  is a front view of a configuration of a blade drive device according to a second embodiment; 
         FIG. 9  is a front view of the blade drive device according to the second embodiment with a flexible print substrate being omitted; 
         FIG. 10  is a cross-sectional view taken along a line C-C in  FIG. 8 ; 
         FIG. 11  is a cross-sectional view taken along a line D-D illustrated in  FIG. 8 ; 
         FIG. 12  is a front view of a variation of the blade drive device according to the first embodiment; and 
         FIG. 13  is a front view of a variation of the blade drive device according to the second embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A description will be given of embodiments according to the present invention with reference to the drawings. 
     First Embodiment 
       FIG. 1  is a front view of a configuration of a blade drive device according to a first embodiment.  FIG. 2  is a cross-sectional view taken along a line A-A in  FIG. 1 .  FIG. 3  is a cross-sectional view taken along a line B-B in  FIG. 1 .  FIG. 4  is a rear view of a blade drive device according to the first embodiment. The blade drive device according to the first embodiment includes: an upper case  10 ; a lower case  20 ; a blade  30 ; a rotor  40 ; iron pieces  50 ,  60 L, and  60 R; coils  70 L and  70 R; and a flexible printed circuit board  80 . 
     The upper and lower cases  10  and  20  serve as a chassis that houses the blade  30 , the rotor  40 , the iron pieces  50 ,  60 L, and  60 R, and a part of the flexible printed circuit board  80 , as illustrated in  FIGS. 2 and 3 . The upper and lower cases  10  and  20  are made of a synthetic resin. The upper case  10  is thicker than the lower case  20 . The blade drive device according to the first embodiment is attachable to an image pickup apparatus or a lens drive apparatus so that the upper case  10  faces the object side and the lower case  20  faces an image pickup element such as a CCD. The upper and lower cases  10  and  20  are respectively provided with openings  11  and  21  for shooting. A slope portion  12  is provided around the opening  11 , as illustrated in  FIG. 3 . Additionally, the upper case  10  is indicated by a broken line in  FIG. 1 . 
     The blade  30  is made of a synthetic resin. The blade  30  is supported to open and close the openings  11  and  21 . The blade  30  swings together with the rotor  40 . The blade  30  illustrated in  FIG. 1  is positioned at a receded position, which is receded from the openings  11  and  21 , and is causing the openings  11  and  21  to be fully opened. 
     The rotor  40  is magnetized with differential magnetic poles in the circumferential direction, and is rotatably supported within the upper and lower cases  10  and  20  serving as a chassis. The rotor  40  has a cylindrical shape. A stopper member  41  is fitted into an inner circumference of the rotor  40 . Thus, the rotor  40  rotates in conjunction with the stopper member  41 . 
     The stopper member  41  has a substantially cylindrical shape made of a synthetic resin. The inner circumference of the stopper member  41  is slidably engaged with a rotor supporting shaft  13  extending in the optical path direction, from the upper case  10 . In this manner, the rotor  40  is rotatably supported. As illustrated in  FIG. 3 , the stopper member  41  is provided with a pin portion  411  extending radially outward from a bottom of the stopper member  41 . The pin portion  411  extends radially outward beyond the outer circumferential surface of the rotor  40 . Additionally, the blade  30  is engaged with the bottom portion of the stopper member  41 . The rotation of the stopper member  41  allows the blade  30  to swing about the rotor supporting shaft  13 . Therefore, the rotation of the rotor  40  swings the blade  30  to open and close the openings  11  and  21 . Additionally, the upper case  10  is provided with restricting pins  14 L and  14 R contactable with the pin portion  411 , as illustrated in  FIGS. 1 and 3 . By causing the pin portion  411  to be contact with the restricting pins  14 L and  14 R, the rotational range of the rotor  40  is restricted. Thus, the swinging range of the blade  30  is also restricted. Further, the lower case  20  is provided with a releasing hole  24  for receiving the thickness of the pin portion  411 , as illustrated in  FIG. 4 . Furthermore, the rotor supporting shaft  13  is engaged with an engagement hole provided in the lower case  20 . 
     The iron pieces  50 ,  60 L, and  60 R are arranged along the inner side surfaces of the upper and lower cases  10  and  20 . The iron pieces  50 ,  60 L, and  60 R surround a substantially entire periphery of the openings  11  and  21  except for the rotor  40 . The iron pieces  50 ,  60 L, and  60 R are connected to one another. The iron piece  50  has a substantially lateral U shape, as illustrated in  FIG. 1 . The iron pieces  60 L and  60 R are respectively connected to end portions of the iron piece  50 , as illustrated in  FIGS. 1 and 2 . The iron pieces  60 L and  60 R are respectively provided with magnetic poles  62 L and  62 R facing the outer circumferential surface of the rotor  40 . Specifically the iron pieces  60 L and  60 R are connected to end portions of two opposed sides of the iron piece  50 , and then orthogonally arranged to the two opposed sides. The iron pieces  60 L and  60 R are arranged to face each other. In addition, the iron piece  60 L is omitted in  FIG. 2 . 
     The iron piece  50  has right-and-left arm portions around which coils  70 L and  70 R are respectively wound. The coils  70 L and  70 R are provided for exciting the iron pieces  50 ,  60 L, and  60 R. The magnetic poles  62 L and  62 R are excited to be different poles by energization of the coils  70 L and  70 R, effecting a magnetically attractive force or magnetically repulsive force on the rotor  40 . Therefore, the rotational force is given on the rotor  40 . In other words, the iron pieces  50 ,  60 L, and  60 R entirely serve as a stator giving the rotational force to the rotor  40 . Accordingly, the rotor  40 , the iron pieces  50 ,  60 L, and  60 R, and the coils  70 L and  70 R serve as an actuator, which is a drive source driving the blade  30 . 
     Additionally, all of the iron pieces  50 ,  60 L, and  60 R are arranged in a substantially rectangular shape when viewed in the optical path direction. Accordingly, the upper and lower cases  10  and  20  each are formed in a rectangular shape when viewed in the optical path direction. The blade  30  is arranged at such a position as to be surrounded by the iron pieces  50 ,  60 L, and  60 R. Further, each of the iron pieces  50 ,  60 L, and  60 R has a flat shape in the optical axis direction. Furthermore, the coils  70 L and  70 R are wound around the iron piece  50 , whereas the coil is not wound around the iron pieces  60 L and  60 R. The iron pieces  60 L and  60 R each has an identical shape. 
     As illustrated in  FIGS. 1 ,  3 , and  4 , a flexible printed circuit board  80  (hereinafter referred to as a FPC) is inserted into the upper and lower cases  10  and  20 . The FPC  80  has flexibility. The FPC  80  is provided with solder lands  81 L,  81 R,  82 L, and  82 R for energizing the coils  70 L and  70 R at its surface facing the lower case  20 . The both ends of the coil  70 L are respectively connected to the solder lands  81 L and  82 L. Similarly, the both ends of the coil  70 R are respectively connected to the solder lands  81 L and  82 L. The solder lands  81 L,  81 R,  82 L, and  82 R are housed within the upper and lower cases  10  and  20  serving as a chassis, and are surrounded by the iron pieces  50 ,  60 L, and  60 R. The FPC  80  is provided with an attachment hole  87 . As illustrated in  FIGS. 1 and 3 , a supporting pin  17  formed in the upper case  10  is inserted into the attachment hole  87 . Further, the supporting pin  17  is engaged with an engagement hole  27 , as illustrated in  FIGS. 3 and 4 . Therefore, the supporting pin  17  functions to connect with the engagement hole  27 , and also functions to fix the FPC  80  at a given position. 
     Additionally, as illustrated in  FIG. 3 , the FPC  80  is inserted into the upper and lower cases  10  and  20  via an insert hole  18  formed in the upper case  10 . The FPC  80  is fixed along the inner surface of the upper case  10 , via a carve portion  88  before reaching the iron piece  50 . 
     Next, a description will be given of the iron pieces  50 ,  60 L, and  60 R.  FIG. 5  is an enlarged view of a connecting portion of the iron pieces  50  and  60 R, as illustrated in  FIG. 2 . As illustrated in  FIG. 5 , at the connecting portion of the iron pieces  60 R and  50 , thin portions  51 R and  61 R are in contact with each other. The thin portions  51 R and  61 R are thinner than another portion of the iron pieces  50  and  60 R, respectively. In addition, the thin portions  51 R and  61 R are respectively formed with fitting holes  55 R and  65 R. A fixing pin  15 R, which is formed in the upper case  10 , is inserted into the fitting holes  55 R and  65 R. Further, an end portion of the fixing pin  15 R is pressure bonded with a bottom edge surface of the iron pieces  50 R by thermal caulking, whereby the thin portions  51 R and  61 R are in pressure contact with each other. This configuration also applies to the fitting holes  55 L and  65 L, and a fixing pin  15 L. 
     Furthermore, as illustrated in  FIG. 5 , the upper case  10  is provided with an engagement pin  16 R adjacent to the fixing pin  15 R. The engagement pin  16 R is engaged with engagement recess portions  56 R and  66 R, which are respectively provided in the thin portions  51 R and  61 R. Unlike the fitting holes  55 R and  65 R, the engagement recess portions  56 R and  66 R are cut out at peripheral surfaces of the iron pieces  50  and  60 R in the optical axis direction. This configuration also applies to an engagement pin  16 L, and engagement recess portions  56 L and  66 L. 
     Furthermore, as illustrated in  FIG. 4 , filling portions which are filled with adhesive materials A are provided at two corner portions on a diagonal line of the upper and lower cases  10  and  20 .  FIG. 6  is a cross-sectional view of the filling portion. As illustrated in  FIGS. 4 and 6 , the filling portion is defined by an embankment portion  19 , a bending portion  29 , and an inner peripheral surface of the corner portion of the upper case  10 . The embankment portion  19 , having a projective shape, is raised toward the lower case  20  from the upper case  10 . The bending portion  29  is carved toward the upper case  10  at an outer edge portion of the lower case  20 . The upper and lower cases  10  and  20  are fixed by the adhesive material a filled in the filling portions. 
     Next, a brief description will be given of an assembling method of the blade drive device according to the first embodiment. Firstly, the rotor  40 , the stopper member  41 , and the blade  30  are integrated with the inner side of the upper case  10  facing upwardly and are then engaged with the rotor supporting shaft  13 . Next, the iron piece  60 R is arranged inside of the upper case  10  so as to respectively engage the fixing pin  15 R and the engagement pin  16 R with the fitting hole  65 R and the engagement recess portion  66 R. In the same manner, the iron piece  60 L is also arranged. In addition, the iron piece  60 R is attached such that the fixing pin  15 R and the engagement pin  16 R are engaged with the fitting hole  65 R and the engagement recess portion  66 R respectively at the same time. The engagement pin  16 R serves to prevent the iron piece  60 R from rotating about the fixing pin  15 R. Therefore, the iron piece  60 R is positioned relative to the upper case  10 . Herein, the iron piece  60 R may be attached such that the fixing pin  15 R and the engagement pin  16 R are in pressure contact with each other. In this case, the iron piece  60 R having a desirable clearance with respect to the rotor  40  can be securely fixed to the upper case  10 . The fitting hole  65 L and the engagement recess portion  66 L of the iron piece  60 L, and the fixing pin  15 L and the engagement pin  16 L are provided in the same manner as the above arrangements. 
     Next, the FPC  80  is attached into the upper case  10  such that the solder land  81  or the like faces the inside of the upper case  10  and the supporting pin  17  is fitted into the attachment hole  87 . Then, the iron piece  50  wound with the coils  70 L and  70 R is attached to the inner periphery of the upper case  10  such that the fixing pins  15 L and  15 R are respectively fitted into the fitting holes  55 L and  55 R, and the engagement pins  16 L and  16 R are respectively engaged with the engagement recess portions  56 L and  56 R. In this case, the iron piece  50  is attached to the upper case  10  such that the thin portion  51 R of the iron piece  50  and the thin portion  61 R are overlapped, and the thin portions  51 L and  61 R are overlapped. Next, the end portions of the fixing pins  15 L and  15 R are melted by thermal caulking, so the end portions of the fixing pins  15 L and  15 R and the outer surface of the iron piece  50  are welded. Further, in order to further securely fix the iron piece  50  to the upper case  10 , the end portions of the engagement pins  16 L and  16 R may be melted by thermal caulking so as to weld with the outer surface of iron piece  50 . Next, the lower case  20  is assembled into the upper case  10  such that the supporting pin  17  is engaged with the engagement hole  27  and that the rotor supporting shaft  13  is engaged with an engaging hole according to the rotor supporting shaft  13 . Then, the adhesive material A is filled into the filling portion to bond the upper and lower cases  10  and  20 . As mentioned above, the blade drive device according to the first embodiment is assembled. 
     Next, a description will be mainly given of a structure for improving handling ability and for maintaining the reduced thickness in the optical axis direction, according to the first embodiment of the blade drive device. A conventional blade drive device includes: a base plate having an opening; a blade, and an actuator for driving the blade. The actuator is typically arranged on an edge portion, of the base plate, receded away from the opening. Thus, a stator is also arranged on the edge portion of the base plate. In a case where the stator is arranged in such a manner, since the base plate is exposed from the outer periphery of the blade drive device and the base plate is typically formed into a thin shape, the base plate may be bended depending on the handling thereof when the blade drive device is assembled or when the assembled blade drive device is installed into an image pickup apparatus or a lens drive apparatus. 
     However, in the blade drive device according to the present embodiment, as mentioned above, the iron pieces  50 ,  60 L, and  60 R serving as the stator are integrated, and are formed along the inner side surfaces of the upper and lower cases  10  and  20 . Therefore, even when the blade drive device is tightly held at its outer periphery, the upper and lower cases  10  and  20  are hardly bent. Accordingly, the handling ability is improved when the blade drive device is assembled and the blade drive device is installed into the mobile phone or the like. 
     Further, since the iron pieces  50 ,  60 L, and  60 R are integrated and are shaped along the inner peripheries of the upper and lower cases  10  and  20 , the operation of the blade  30  is ensured even when an impact is applied to the blade drive device from its external. Therefore, the impact resistance is improved. In particular, when the impact is applied to the side of the blade drive device, the impact resistance is improved. Further, the optical axis direction thickness of the upper and lower cases  10  and  20 , which serve as the chassis, corresponds to the thicknesses of the coils  70 L and  70 R, as illustrated in  FIG. 2 . Typically, the coil for exciting the stator is thicker than any other parts in the blade drive device. Therefore, the thickness of the upper and lower cases  10  and  20  corresponds to the thicknesses of the coils  70 L and  70 R, thereby improving the handling ability and maintaining the reduced thickness in the optical axis direction. 
     Additionally, as illustrated in  FIG. 1 , the solder lands  81 R,  81 L,  82 R, and  82 L provided in the FPC  80  are housed within the upper and lower cases  10  and  20 , and are surrounded by the iron pieces  50 ,  60 L, and  60 R. With such a configuration, when the blade drive device is assembled, the coil break due to deflecting of the blade drive device can be prevented, and the handling ability is improved. Further, the FPC  80  is inserted into the upper and lower cases  10  and  20  via these side surfaces, thereby maintaining the reduced thickness of the blade drive device in the optical axis direction. In addition, the conventional blade drive device includes a drive pin, which is attached to the rotor, which protrudes outwardly, and which bends downwardly in the optical axis direction. Such a drive pin is engaged with an engagement hole formed on a blade to drive the blade. In this manner, the drive pin bends downwardly in the optical axis direction. This is one of factors that increase the thickness of the conventional blade drive device in the optical axis direction. However, in the blade drive device according to the first embodiment, since the blade  30  is attached to the rotor  40 , as illustrated in  FIG. 3 , the reduced thickness can be maintained in the optical axis direction. Furthermore, this eliminates the drive pin for transmitting the driving force from the rotor to the blade, thereby decreasing the number of the parts. 
     In addition, the blade  30  is directly fixed to the stopper member  41 , as illustrated in  FIG. 3 . In the present embodiment, the blade  30  and the stopper member  41  are separately provided. However the blade  30  and the stopper member  41  may be integrated. Therefore, the number of the parts can be further reduced. In addition, in the present embodiment, the rotor supporting shaft  13 , which serves as a spindle for supporting the rotation of the rotor  40 , is integrally formed in the upper case  10 . However, the invention is not limited to this configuration. For example, a rotor shaft which rotates in conjunction with the rotor may be employed. In this case, the blade  30  may be directly fixed to the rotor shaft, or the blade  30  may be integrally formed with the rotor shaft. 
     Returning to  FIG. 6 , the filling portions, for filing the adhesive material A for fixing the upper and lower cases  10  and  20 , are provided in the upper and lower cases  10  and  20 . In this manner, the upper and lower cases  10  and  20  are fixed by the adhesive material A. In the conventional blade drive device, a projection, which is projected in the optical axis direction, is formed in one of the upper and lower cases  10  and  20 . A fitting hole, which is fitted with the projection, is formed in the other of the upper and lower cases  10  and  20 . The end portion of the projection, which is fitted into the fitting hole, is welded by thermal caulking, thus the both are fixed. In this manner, the fixation by thermal caulking causes the end portion of the projection to be slightly melted. This is one of factors that increase the thickness in the optical axis direction. However, as the blade drive device according to the present embodiment, the upper and lower cases  10  and  20  are fixed by an adhesive material, the reduced thickness can be maintained in the optical axis direction. 
     Further, although the upper and lower cases  10  and  20  are fixed by the adhesive material, the present invention may employ another configuration. For example, the upper and lower cases  10  and  20  may be fixed by snap fitting.  FIG. 7  is an exemplary cross-sectional view of a snap fitting structure. As illustrated in  FIG. 7 , the upper and lower cases  10  and  20  may be respectively provided with an engagement piece  19   s  and an engagement hole  29   s  corresponding to each other such that the engagement piece  19   s  and the engagement hole  29   s  do not exceed the thickness in the optical axis direction when the upper and lower cases  10  and  20  are assembled. In this case, the space where the adhesive material is filled is unnecessary, thereby maintaining the reduced thickness in the optical axis direction and also reducing the size in the planar direction perpendicular to the optical axis direction. 
     Additionally, since the iron pieces  50 ,  60 L, and  60 R, serving as the stator, have flat shapes in the optical axis direction, as illustrated in  FIGS. 2 and 3 , the reduced thickness can be maintained in the optical axis direction. In particular, as illustrated in  FIG. 5 , in the connecting portion of the iron piece  50  and the iron pieces  60 L and  60 R, the thin portions  51 L and  51 R of the iron piece  50  are respectively overlapped with the thin portions  61 L and  61 R in the optical axis direction, when the iron pieces  60 L and  60 R are connected to the iron piece  50 . Therefore, the reduced thickness can be maintained in the optical axis direction. 
     As mentioned above, each of the upper and lower cases  10  and  20  has a rectangular shape as seen in the optical axis direction, and the iron pieces  50 ,  60 L, and  60 R are arranged to have a rectangular shape, as seen in the optical axis direction so as to correspond to the shapes of the upper and lower cases  10  and  20 . With such a configuration, in the case where the rectangular shape is formed, the area where the solder lands  81 R,  81 L,  82 R, and  82 L are formed is ensured widely, as compared with a case where a circular shape is formed as seen in the optical axis direction. Therefore, the space for arranging components can be effectively used. Further, the handling is facilitated after the assembly is finished. 
     Next, a description will be given a structure for positioning and fixing the drive source relative to the upper case  10 . As illustrated in  FIGS. 1 and 2 , the iron pieces  50 ,  60 L, and  60 R serving as the stator are fitted onto the fixing pins  15 R and  15 L and the engagement pins  16 R and  16 L so as to be positioned and fixed. Conventionally, the outer periphery of the stator is in pressure contact with positioning pins provided on a board to position and fix the stator. However, when such positioning pins, which are in pressure contact with the outer periphery of the stator, are provided on the board or the like, the size cannot be reduced in the planar direction perpendicular to the optical axis direction. In the blade drive device according to the first embodiment, the fitting hole  55 R or the likes, which fitted onto the fixing pin  15 R or the like, is provided in the iron piece  50  or  60 R. Therefore, the pins, which come into contact with the periphery of the stator, can be eliminated, thereby reducing the size of the upper and lower cases  10  and  20  in the planar direction. Accordingly, the size of the blade drive device can be reduced in the planar direction. 
     Further, as illustrated in  FIG. 2 , the end portion of the fixing pin  15 R is thermally caulked. This securely fixes the iron pieces  50  and  60 R on the upper case  10 . In addition, since the fixing pin  15 R is fitted into the fitting hole  55 R of the iron piece  50  and the fitting hole  65 R of the iron piece  60 R, even when the stator is composed of plural iron pieces, the increase in the number of the parts can be prevented, and the size can be reduced in the planar direction. 
     Next, regarding the blade drive device according to the first embodiment, a description will be given of a structure for improving the shutter speed while the smaller size is maintained. 
     As mentioned above, the iron pieces  50 ,  60 L, and  60 R are connected to each other and arranged to surround substantially the entire peripheries of the openings  11  and  21 . With such an arrangement, the total length of the iron pieces  50 ,  60 L, and  60 R serving as the stator can be ensured, and the number of the turns of the coils  70 L and  70 R can be increased. Therefore, the output power of the rotor  40  is increased and the shutter speed becomes faster. In addition, the iron pieces  50 ,  60 L, and  60 R are arranged to surround the substantially entire peripheries of the openings  11  and  21 , thereby maintaining the small size of the entire iron pieces  50 ,  60 L, and  60 R in the planar direction perpendicular to the optical axis direction. 
     In addition, the iron pieces  50 ,  60 L, and  60 R are formed into a substantially rectangular shape as a whole, thus making its linear portion as long as possible. It is therefore possible to wind the coils  70 L and  70 R in a great number of turns around the linear portion where the winding is made easy. Moreover, the coils  70 L and  70 R are wound respectively around two opposed sides of the iron piece  50 , thereby increasing the number of the turns of the coil. Also, the rotor  40  is located at a center portion of one side of the rectangle. When the rotor  40  is located at such a position, it is suitable for the coils  70 L and  70 R are suited to be respectively wound around two opposing sides of the iron piece  50 . 
     In addition, when the stator is integrally formed as the conventional stator and is formed into a complicated shape such that the openings  11  and  21  are surrounded as the blade drive device according to the present embodiment, the winding of the coil around the stator may become difficult. However, the stator, which is employed in the blade drive device according to the present embodiment, is composed of the iron pieces  50 ,  60 L, and  60 R which are connected, as mentioned above. Therefore, the coils  70 L and  70 R are wound around the iron piece  50  before the iron pieces  50 ,  60 L, and  60 R are connected, and then they are connected, thereby improving the winding workability. 
     Second Embodiment 
     Next, a description will be given of a blade drive device according to a second embodiment with reference to the drawings. Additionally, in the blade drive device according to the second embodiment, components that are similar to those of the first embodiment will be denoted by the same reference numerals as used in connection with the first embodiment, and a detailed description of such components will be omitted. 
       FIG. 8  is a front view of a configuration of the blade drive device according to the second embodiment.  FIG. 9  is a front view of the blade drive device according to the second embodiment with a flexible print substrate being omitted.  FIG. 10  is a cross-sectional view taken along a line C-C in  FIG. 8 . 
     As illustrated in  FIGS. 8 and 9 , a rotor  40   a  is located at a corner portion of upper and lower cases  10   a  and  20   a  each has a rectangular shape as seen in the optical axis direction. Additionally, iron pieces  50 La and  50 Ra serve as a stator and each has an identical L shape. The iron pieces  50 La and  50 Ra are arranged to be a rectangular shape, to surround the periphery of openings  11   a  and  21   a , and to be along inner side surfaces of the upper and lower cases  10   a  and  20   a . One ends of the iron pieces  50 La and  50 Ra are respectively provided with magnetic poles  52 La and  52 Ra which face the rotor  40   a . Further, the other ends of the iron pieces  50 La and  50 Ra are connected to each other. The iron pieces  50 La and  50 Ra are respectively provided with fitting holes  55 La and  55 Ra, which are respectively engaged with fixing pins  15 La and  15 Ra formed in the upper case  10   a . The fixing pins  15 La and  15 Ra are provided near a stopper member  41   a.    
     A coil bobbin  90   a  is assembled onto the iron pieces  50 La and  50 Ra. The coil bobbin  90   a  is made of a synthetic resin. As illustrated in  FIGS. 8 and 9 , the coil bobbin  90   a  includes: two arm portions around which the coils  70 La and  70 Ra are respectively wound; flange portions  91 La and  92 La provided at both ends of one of the two arm portions; and the flange portions  91 Ra and  92 Ra are provided at both ends of the other of the two arm portions. As illustrated in  FIG. 9 , the flange portions  91 La and  91 Ra are respectively provided with terminal portions  94 La and  94 Ra for respectively winding ends of the coils  70 La and  70 Ra. Herein, the coils  70 La and  70 Ra are composed of a single wire. This wire is connected to solder lands  81   a  and  82   a  formed on a FPC  80   a , and is indicated by a dashed line in  FIG. 8 . Further, the coil bobbin  90   a  is provided with a thin portion  93   a  connecting the flange portions  92 La and  92 Ra. The thin portion  93   a  is thinner than other portions such as the flange portion  92 La, and is bendable. The coil bobbin  90   a  is bended via the thin portion  93   a  such that the flange portions  92 La and  92 Ra are perpendicular to each other, as illustrated in  FIGS. 8 and 9 . 
     Further, the FPC  80   a  is provided with a relief opening  86   a  for ensuring an optical path passing through the openings  11   a  and  21   a , as illustrated in  FIG. 8 . The FPC  80   a  is provided with a relief opening  84   a  for preventing the interference with the rotation of the rotor  40   a . The FPC  80   a  are provided with through holes  85 La and  85 Ra through which the fixing pins  15 La and  15 Ra are penetrated.  FIG. 11  is a cross-sectional view taken along a line D-D illustrated in  FIG. 8 . As illustrated in  FIG. 11 , the FPC  80   a  is inserted into the upper and lower cases  10   a  and  20   a  via an insert hole  18   a  formed in the upper case  10   a . The FPC  80   a  is bended at a bending portion  88   a  and arranged along the inner surface of the lower case  20   a . Moreover, the solder lands  81   a  and  82   a  are arranged within the upper and lower cases  10   a  and  20   a  to be surrounded by the iron pieces  50 La and  50 Ra. 
     Further, as illustrated in  FIG. 11 , the fixing pin  15 La is fitted into the fitting hole  55 La formed in the iron piece  50 La, an end portion of the fixing pin  15 La is fixed in the upper case  10   a  by thermal caulking. This configuration also eliminates a positioning pin which abuts with the periphery of the stator, thereby maintaining the small sizes of the upper and lower cases  10   a  and  20   a  in the planar direction. Accordingly, the small size of the blade drive device in the planar direction can be maintained. Additionally, the fixing pin  15 La may be press fitted into the fitting hole  55 La. In this case, the iron piece  50 La can be securely fixed to the upper case  10  with a desirable certain clearance between the iron piece  50 La and the rotor  40   a.    
     Furthermore, the blade  30   a  is fixed to the stopper member  41   a , and the stopper member  41   a  is rotated in conjunction with the rotor  40   a , as illustrated in  FIG. 10 . That is, the blade  30   a  is attached to the rotor  40   a  via the stopper member  41   a . Also, referring to  FIG. 10 , thin portions  51 La and  51 Ra are formed on the connecting portions of the iron pieces  50 La and  50 Ra, respectively. Further, stage portions  16   a  and  26   a  for supporting this connecting portion are respectively formed in the upper and lower cases  10   a  and  20   a . The stage portions  16   a  and  26   a  respectively abut with the upper surface of the thin portion  51 La and the lower surface of the thin portion  51 Ra. In addition, the coil bobbin  90   a  and the coil  70 La are omitted in  FIG. 10 . 
     The blade  30   a  illustrated in  FIG. 9  is positioned at a receded position in which the blade  30   a  is receded from the openings  11   a  and  21   a . The blade  30   a  in the receded position is arranged to partially overlap the iron piece  50 Ra in the optical path direction. In more details, the blade  30   a  is arranged between the iron piece  50 Ra and the lower case  20   a  in the optical path direction. With such a configuration, the small size in the planar direction can be maintained. Furthermore, as illustrated in  FIG. 9 , both of the coils  70 Ra and  70 La are wound in such a position not to interfere with the blade  30   a  positioned at the receded position. Accordingly, the small size in the planar direction can be maintained. 
     Moreover, the coil bobbin  90   a  is bendable via the thin portion  93   a , as mentioned above. Even when the stator has a rectangular shape in this manner, the coil can be wound around two sides, which do not oppose to each other, of the stator having the rectangular shape. Therefore, the number of the turns of the coil can be increased by means of the single coil bobbin  90   a.    
     Next, a description will be given of a variation of the blade drive device according to the first embodiment with reference to  FIG. 12 .  FIG. 12  is a front view of the variation of the blade drive device according to the first embodiment.  FIG. 12  corresponds to  FIG. 1 . As illustrated in  FIG. 12 , a control IC  100 , for controlling current in the coils  70 L and  70 R, is mounted on a FPC  80 A. The control IC  100  is mounted on a surface, of the FPC  80 A, facing the lower case  20 . In this manner, the control IC  100  is also mounted to be surrounded by the iron pieces  50 ,  60 L, and  60 R, thereby improving the handling ability of the blade drive device. Also, the control IC  100  is housed within the upper and lower cases  10  and  20 , thereby making the blade drive device and the control IC  100  into a single unit, and thereby making the handling of the blade drive device easy. Further, the space within an external device equipped with the blade drive device can be effectively used. 
     Next, a description will be given of a variation of the blade drive device according to the second embodiment with reference to  FIG. 13 .  FIG. 13  is a front view of a variation of the blade drive device according to the second embodiment.  FIG. 13  corresponds to  FIG. 8 . As illustrated in  FIG. 13 , a control IC  100   a , for driving the rotor  40   a , is mounted on a FPC  80 Aa. The control IC  100   a  is also mounted on a surface, of the FPC  80 Aa, facing a lower case  20   a . With such a configuration, the handling ability of the blade drive device is also improved. Further, the blade drive device and the IC  100   a  can be integrated into a single unit, thereby making the handling of the blade drive device easy and effectively using space within an external apparatus equipped with the blade drive device. 
     While the preferred embodiments of the present invention have been illustrated in detail, the present invention is not limited to the above-mentioned embodiments, and other embodiments, variations and modifications may be made without departing from the scope of the present invention. 
     The blade defines the fully open and close states. However, the blade may adjust the opening rate of the opening. Plural blades may be provided. 
     The embodiments have illustrated the blade  30  made of a synthetic resin. However, the blade  30  may be made of a typically antireflective film of a light shielding film, like a somablack film (Somar Corporation), for example. 
     Additionally, plural motors may be provided. For example, as described in the second embodiment, when the two iron pieces each has a L shape, the two rotors are arranged on a diagonal line with the opening set as a center. 
     The second embodiment has illustrated the configuration in which the iron pieces  50 La and  50 Ra are supported by the stage portions  16   a  and  26   a . However, a fixing pin formed in the upper case may be fitted into the fitting holes formed in the iron pieces  50 La and  50 Ra, and then an end portion of the fixing pin may be fixed to the fitting holes by thermal caulking. Alternately, by pressure fitting the fixing pin into the fitting hole, the iron pieces  50 La and  50 Ra may be securely fixed to the upper case. 
     The second embodiment has illustrated the terminal portions  94 La and  94 Ra, around which the end portions of the coils  70 La and  70 Ra are respectively wound, are provided in the flange portions  91 La and  91 Ra of the coil bobbin  90   a , respectively. However, the coil bobbin without the terminal portions  94 La and  94 Ra may be employed. 
     Further, a sheet of a ND filter may cover the opening. 
     Finally, several aspects of the present invention are summarized as follows. 
     According to an aspect of the present invention, there is provided a blade drive device including: a blade; a drive source that drives the blade; and a chassis that has an opening opened and closed by the blade and that houses the blade and the drive source, the drive source including: a rotor that is rotatably supported; a stator around which a coil for excitation is wound and which applies a rotational force to the rotor, and the stator being arranged to surround a periphery of the opening. 
     With such a configuration, the stator is arranged to surround the periphery of the opening, reducing the size of the blade drive device in the planar direction perpendicular to the optical axis direction, and ensuring the entire length of the stator. This increases the number of coil turns. Therefore, the blade drive device can be reduced in size and the shutter speed can be improved. Further, since the blade and the drive source are housed in the chassis, the blade drive device can be made to be a single unit. Thus, this facilitates an assembling workability of this blade drive device assembled into a variety of lens drive devices or the like. 
     In the above configuration, the stator may have a rectangular shape. 
     The stator has a rectangular shape, thereby making one side of the stator as long as possible. Thus, the coil can be wound around a linear portion, around which the coil is readily wound, in such a manner that the number of coil turns is large. 
     In the above configuration, the coil may be wound at least two sides of the stator. 
     The coil is wound around two sides of the rectangular-shaped stator, thereby increasing the number of coil turns. 
     In the above configuration, the rotor is located at a center portion of one side of the stator, and the coil is wound around two opposing sides of the stator. 
     This configuration can also increase the number of coil turns. 
     In the above configuration, the rotor may be located at a corner portion of the stator, the coil may be wound around two sides of the stator, and the two sides do not oppose to each other. 
     This configuration can also increase the number of coil turns. 
     In the above configuration, the stator may have a flat shape in an optical direction. 
     This configuration can maintain the reduced thickness in the optical axis direction. 
     In the above configuration, the stator may include a plurality of iron pieces mutually connected, and each of the plurality of iron pieces may have a thin portion thinner than another portion at a connecting portion where the plurality of iron pieces are connected to each other. 
     With such a configuration, the plural iron pieces are connected at their thin portions, thereby maintaining the reduced thickness in the optical axis direction. 
     In addition, in a case where a stator is integrally formed and has a complicated shape to surround the periphery of the opening, the workability of winding a coil around the stator may be difficult. However, since the stator is composed of the iron pieces connected, the coil is wound around any of the iron pieces before the iron pieces are connected. Then, the iron pieces are connected to improve the workability in winding a coil. 
     In the above configuration, the blade may be positioned at a receded position receded from the opening with overlapping the stator in an optical axis direction. 
     This maintains the reduction in size in the planar direction. 
     In the above configuration, the coil may be wound around at a position where the stator does not interfere with the blade positioned at the receded position. 
     This maintains the reduction in size in the planar direction. 
     In the above configuration, a control IC for controlling energization of the coil may be mounted on the printed substrate, and the control IC may be housed in the chassis and surrounded by the stator. 
     With such a configuration, the blade drive device and the control IC can be unitized and its handling can be facilitated. Further, a space in an external device equipped with the blade drive device can be effectively used.