JP2007033602A - Blade drive device for camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a blade drive device for a camera, which is provided with one blade and is most suitable for size reduction of the device. <P>SOLUTION: The one shutter blade 3 rotatably attached to a shaft 1m on a base plate 1 and used to open and close an aperture part 1a is made of a synthetic resin and has a long hole 3a. A balance plate 4 rotatably attached to a shaft 1n on the base plate 1 is made of a metal and has a long hole 3a. The drive pin 12c of a driving means is fit in the long holes 3a and 4a. Accordingly, the shutter blade 3 is rotated by the drive pin 12c and is likely to bound when coming into contact with stoppers 1p and 1q. However, rotating force of the balance plate 4 suitably restrains the bound. Consequently, this makes it possible to reduce the size of the shutter blade and hence the size of a shutter device. In addition, in case where an impact is applied to the camera, the balance plate 4 restrains the shutter blade 3 from overrunning. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a camera blade drive device including a single blade, such as a shutter blade, a diaphragm blade, a filter blade, a barrier blade, and the like, which moves forward and backward to an opening for a photographing optical path.

  Some shutter devices are mainly incorporated in digital still cameras and cameras for small information terminal devices such as mobile phones, and open and close the exposure opening by reciprocating a single shutter blade. It is known (see Patent Document 1). Also, in recent diaphragm devices, a single diaphragm blade having a small circular diaphragm aperture is caused to enter the exposure aperture, thereby taking a picture with a small aperture and leaving it in a retracted state. Is known (see Patent Documents 1 and 2), but such an aperture device is employed in both silver salt film cameras and digital cameras.

  As with the diaphragm device, there is an ND filter device that reduces the amount of photographing light. However, as a recent ND filter device, a circular opening like the above-described diaphragm blade (the opening in this case is an exposure opening). An ND filter plate is attached to the blade member that is formed to cover the opening to form a filter blade, and is operated in the same manner as the diaphragm blade described above. Is known (see Patent Document 2). Such a filter device is employed in both a silver salt film camera and a digital camera.

  In addition, some cameras have a lens barrier device in which the front surface of the photographic lens is covered with a plate member so that the photographic lens is not soiled or damaged when not in use such as when carried. Some of the lens barrier devices are provided, but some of the lens barrier devices operate the plate member in the same manner as the shutter blades. Therefore, the plate member operated in this way is said to be a barrier plate or a barrier blade, but in the case of such a barrier blade, only one sheet may be required. Such a lens barrier device can be employed for both a silver salt film camera and a digital camera.

  In such various apparatuses, each blade member may be driven by a spring. However, recently, there have been an increasing number of devices driven by electromagnetic actuators. As the electromagnetic actuator, a step motor or electromagnetic plunger may be used, but recently, a current-controlled actuator, which is said to be a moving magnet type motor, is advantageous for cost reduction and downsizing. It has become. Also, in the case of this actuator, various configurations are known. Regardless of the configuration, basically a permanent magnet magnetized in two or four poles in the radial direction. The manufactured rotor can be rotated only within a predetermined rotation angle range by applying a rotational force in a direction corresponding to the energization direction to the stator coil. Then, when the output pin of the rotor is used as a drive pin and directly fitted into the hole of the blade member, a drive member (also referred to as an opening / closing lever) that is reciprocally rotated by the output pin of the rotor is interposed, In some cases, the drive pin provided on the drive member is fitted into the hole of the blade member.

JP 2003-66506 A JP 2001-188275 A

  In each blade driving device as described above, the reason for using one blade member that advances and retreats to the photographing opening may be a reduction in cost, but rather than the plane of the ground plate to which the blade member is attached. This is because the area is desired to be reduced. In other words, when the opening for the photographing optical path is fully opened, it is necessary to reduce the housing area of the blade member and to reduce the size of the entire apparatus. And the request | requirement of reducing the whole apparatus in that way still exists even when it is a case where the blade member is made into one sheet. For this reason, in a blade driving device having a single blade member, in order to reduce the accommodation area of the blade member without changing the size of the opening for the photographing optical path, the blade member is advanced and retracted into the opening. The outer shape of the part to be made should be made as small as possible so as to be as close as possible to the size of the opening, and in the retracted state where the opening is fully opened, it should be stopped close to the edge of the opening. Become.

  However, such a configuration is not easy. That is, when the blade member enters the opening and retracts from the opening, the blade member is brought into contact with the stopper and stopped. Therefore, when trying to reduce the plane area of the main plate by making the blade member as small as possible and placing it close to the opening in the retracted state, the blade member abuts against the stopper when entering the opening. The time until the outer peripheral edge of the blade member returns to the inside of the opening, and a gap is generated between the edge of the opening and the outer peripheral edge of the blade member, and temporarily stops although it bounces temporarily. Makes it longer. Such a situation is fatal for the shutter device, without needing to be specifically described. In addition, for the diaphragm device and the filter device, it becomes a factor for delaying an actual photographing time to be performed thereafter. Furthermore, in the case of a lens barrier device, it is a factor that deteriorates the appearance and lowers the commercial value.

  On the other hand, when the blade member is operated from the state of entering the opening to the retracted state, immediately after opening the opening, the blade member abuts against the stopper and bounces, and the outer periphery of the blade member temporarily opens. Part of the cover, and it takes a long time to completely stop and obtain a stable fully open state. The occurrence of such a situation is fatal for the shutter device. In addition, for the diaphragm device and the filter device, it becomes a factor of increasing the time until the next photographing can be performed. Further, in this case, the lens barrier device also deteriorates the appearance and decreases the commercial value.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a single blade that advances and retreats to a photographing opening, and the opening is fully opened. In the retracted state, even if the outer peripheral edge of the blade is arranged close to the edge of the opening, it can be reduced in size so that it can be stopped properly by contacting the stopper when the operation ends. It is to provide an optimal camera blade driving device. Another object of the present invention is to provide a camera blade driving device that can stably obtain a stopped state of the blades when the blade driving means is the above-described moving magnet type motor.

  In order to achieve the above object, a camera blade driving device according to the present invention includes a ground plate having an opening for a photographing optical path and two stoppers, and is rotatably attached to the ground plate. There is a long hole in the vicinity of the attachment part, and one blade that advances and retreats to the opening part by reciprocating rotation, and is attached rotatably to the ground plate, and has a long hole in the vicinity of the attachment part. A balance plate, and a drive pin inserted into both the long hole of the blade and the long hole of the balance plate, and the blade and the balance plate are made to oppose each other by reciprocating the drive pin. Driving means for rotating in the direction and moving only the blades to and from the opening, and the blades abut against the stoppers when they enter the opening and retreat from the opening. Let me So as to.

  In that case, if the blades are made of synthetic resin and the balance plate is made of metal, and the two have substantially the same weight, the moment of inertia of the two becomes substantially equal, and the blades abut against the stopper. When it does, it becomes possible to stop suitably. Further, the drive means is a motor comprising a stator having a coil and a rotor having a permanent magnet, and the drive pin is an output pin that reciprocally rotates in a predetermined angular range integrally with the rotor. The rotor is particularly effective for use in a digital camera if the rotational force is applied in the direction in which the blade comes into contact with the stopper by the magnetic force of the permanent magnet when the coil is not energized. A small blade driving device is obtained.

  The camera blade drive device of the present invention is mounted to be rotatable with respect to the ground plane, and is rotated with respect to the ground plane in addition to a single blade that is advanced and retracted to the opening for the photographing optical path by the reciprocating operation of the drive pin. Since the balance plate that is attached and can be rotated simultaneously in the opposite direction to the blade by reciprocating operation of the drive pin is provided, even when the blade enters the opening and contacts the stopper, In addition, when retreating from the opening and coming into contact with the stopper, the bounce is suppressed and the stop is preferably performed. Therefore, in the fully open state of the opening, the blades can be disposed close to the opening, the plane area of the ground plane can be reduced, and the apparatus can be downsized. Further, when the driving means is a moving magnet type motor, even if a large impact is applied to the camera when not in use, the runaway of the blades can be suppressed by the presence of the balance plate.

  Embodiments of the present invention will be described with reference to the illustrated examples. As described above, the present invention can be applied to any of a shutter device, a diaphragm device, a filter device, and a lens barrier device provided with a single blade that advances and retreats to an imaging opening. However, the embodiment is a configuration example when applied to a shutter device for a small digital still camera. 1 is a front view showing a fully opened state of the shutter blades, and FIG. 2 is a cross-sectional view of a main part in a closed state of the shutter blades. 3 is a front view showing a state in which the flexible printed wiring board is removed from FIG. 1, and FIG. 4 is a rear view of FIG. Further, FIG. 5 is a front view showing the closed state of the shutter blades in the same manner as FIG. 3, and FIG. 6 is a rear view of FIG.

  First, the structure of a present Example is demonstrated using FIGS. 1-4. The base plate 1 is made of a synthetic resin and has a circular opening 1a for a photographing optical path. The cover plate 2 shown in FIG. 4 is made of metal, and has a circular opening 2a for the photographing optical path in a region facing the opening 1a of the base plate 1. Since the opening 2a has a diameter larger than that of the opening 1a of the base plate 1, the exposure opening is restricted by the opening 1a. The base plate 1 and the cover plate 2 constitute a blade chamber between the two by attaching the cover plate 2 to the base plate 1. In the present embodiment, the opening 1a of the base plate 1 regulates the exposure opening. However, the opening 2a of the cover plate 2 is exposed by reversing the sizes of the opening 1a and the opening 2. You may make it regulate opening.

  Here, how to attach the cover plate 2 to the main plate 1 will be described. As shown in FIG. 4, shafts 1 b, 1 c, 1 d, 1 e, and 1 f are erected on the base plate 1 on the cover plate 2 side. Among these, the shafts 1c and 1f are shafts for positioning the base plate 1 and the cover plate 2, and the shaft 1c is inserted into an oval hole formed in the cover plate 2, and the shaft 1f is a cover. It is inserted into a circular hole formed in the plate 2. The shaft 1f also serves to attach the ground plate 1 and the cover plate 2 together with the shafts 1b, 1d, and 1e inserted into the holes of the cover plate 2. That is, after the four shafts 1b, 1d, 1e, and 1f are inserted into the holes formed in the cover plate 2, their tips are heat-melted and deformed into a substantially circular bowl shape larger than the shaft diameter. The cover plate 2 is prevented from being removed from the shafts 1b, 1d, 1e, and 1f. (Refer to the case of axes 1e and 1f in FIG. 2)

  Next, a configuration for attaching the base plate 1 to the camera body will be described. In FIG. 1, an oval hole 1 g and a circular hole 1 h are formed on the right side of the base plate 1. As shown in FIG. 4, shaft-shaped receiving portions 1 i, 1 j, and 1 k are provided on the surface of the base plate 1 on the cover plate 2 side, of which the receiving portion 1 j is the cover plate 2. It penetrates the hole 2b formed in the. Therefore, first, the oval hole 1g is fitted to a positioning shaft provided in the camera body disposed on the base plate 1 side. Then, after the circular holes 1h are overlaid on the screw holes formed on the camera body side, screws are inserted into the holes from the cover plate 2 side and screwed. Thereafter, a third member such as a lens barrel (not shown) is attached to the camera body from the cover plate 2 side. At this time, the tips of the receiving portions 1i, 1j, and 1k serve as contact surfaces for the third member. Thus, the cover plate 2 is prevented from being deformed.

  As shown in FIG. 4, the base plate 1 attached to the camera body is provided with two shafts 1m and 1n and two stoppers 1p and 1q on the surface on the cover plate 2 side. Among them, the shafts 1m and 1n have their tips inserted into holes 2c and 2d formed in the cover plate 2, respectively. In the blade chamber, a synthetic resin shutter blade 3 having a long hole 3a is rotatably attached to the shaft 1m, and a metal balance plate 4 having a long hole 4a is attached to the shaft 1n. In order to do this, a not shown in FIGS. 3 and 5 is rotatably mounted. As shown in FIG. 4, the cover plate 2 is formed with an arc-shaped long hole 2e. However, the base plate 1 has substantially the same shape so as to overlap the long hole 2e. The elongated hole 1r is formed.

  Next, the unit configuration of the actuator attached to the surface outside the blade chamber of the main plate 1 will be described. The actuator of this embodiment is the above-described current control type motor, but its specific configuration is basically of the type known from Japanese Patent Application Laid-Open No. 2000-60088. First, the configuration of the stator will be described. As can be seen from FIG. 2, the stator frame of this embodiment has a flat plate-like first coil frame 5 and a closed wall at the upper end of the cylindrical portion, and has a cup shape as a whole. A rotor, which will be described later, is arranged in a storage chamber constituted by the second coil frame 6 and constituted by them. In this embodiment, the stator frame is constituted by two members (the first stator frame 5 and the second stator frame 6) as described above. For example, the second stator of this embodiment is used. The frame 6 may be divided into two members and constituted by three members.

  On the outside of the first stator frame 5 and the second stator frame 6, a concave groove is formed with a predetermined width, and the first stator frame 5 and the second stator frame 6 are combined. In such a state, these concave grooves become one annular groove surrounding the accommodation chamber in the vertical direction in FIG. 2, and the two stator frames 5 and 6 are integrated by winding the coil 7 therearound. ing. The closing wall of the second stator frame 6 is provided with two terminal pins 6a and two positioning pins 6b, and the coil 7 wound around the two stator frames 5 and 6 as described above. Are wound around the two terminal pins 6a. Further, after the coil 7 is wound around the two stator frames 5 and 6 in this way, a cylindrical yoke 8 is fitted to the outside thereof. Furthermore, four known magnetic rods 9 are embedded in the second stator frame 6. Unlike the present embodiment, when two coils are wound, four terminal pins 6a as described above are required.

  As can be seen from FIG. 2, the first stator frame 5 is provided with a recess, and the photosensor 10 is press-fitted there. Further, the flexible printed wiring board 11 as shown in FIG. 1 supplies two currents to the two positioning pins 6b of the second stator frame 6 in order to supply current to the photosensor 10 and the coil 7. Four metal pins (two for the light emitting part and two for the light receiving part) provided in the photosensor 10 with the holes fitted therein, and two terminals of the second stator frame 6 Soldered to both ends of the coil 7 wound around the pin 6a.

  In the case of the present embodiment, the photosensor 10 is a direct-type photo in which the light emitting part and the light receiving part are arranged at opposing positions so that the light emitted from the light emitting part directly enters the light receiving part. Although it is a sensor, it may be a reflective photosensor in which light emitted from the light emitting unit is reflected by a predetermined reflecting means and is incident on the light receiving unit. In that case, the light emitting unit and the light receiving unit are arranged adjacent to each other. However, the reflecting means may be provided at the position of the light receiving portion in the direct photosensor or may be provided on the light shielding wall 12d to be described later. The H level signal is reversed.

  Next, the configuration of the rotor that is supported in the above-described accommodation chamber will be described. The rotor 12 of the present embodiment has a permanent magnet 12a magnetized in two poles in the radial direction, and a rotating shaft made of synthetic resin is connected to the first stator frame 5 and the second stator frame 6. It is bearing at. A synthetic resin arm 12b extending radially from the peripheral surface of the permanent magnet 12a is provided with a drive pin 12c and a light shielding wall 12d extending in opposite directions parallel to the rotation axis. And the drive pin 12c penetrates the circular arc-shaped long hole 1r formed in the base plate 1, is fitted into the long hole 3a of the shutter blade 3 and the long hole 4a of the balance plate 4 in the blade chamber, and the tip thereof Is inserted into the arc-shaped elongated hole 2 e of the cover plate 2. Further, the light shielding wall 12d can be moved back and forth in the detection optical path of the photosensor 10. In the rotor 12 of this embodiment, the other part of the rotor 12 is integrally formed with the cylindrical permanent magnet 12a by so-called outsert processing using a synthetic resin material. May be formed of a synthetic resin material (plastic magnet material) mixed with magnetic particles.

  Next, the attachment structure to the main plate 1 of the actuator having such a unit structure will be described. First, as can be seen from FIG. 2, the first stator frame 5 is provided with two positioning pins 5 a on the lower surface thereof and is fitted in respective holes provided in the base plate 1. As can be seen from FIGS. 1 and 3, the ground plate 1 is provided with three hook portions 1 s having flexibility, and as shown in FIG. 2, they are hung on the first stator frame 5. This prevents the first stator frame 5 and thus the actuator unit from moving upward. Then, the flexible printed wiring board 11 is placed on the positioning pins 1t and 1u provided on the base plate 1 as shown in FIG. 1 in order to prevent an excessive force from being applied to each soldering portion. The holes 11a and 11b are fitted.

  Next, the operation of this embodiment will be described with reference to FIGS. As described above, the present embodiment is configured as a shutter device for a small digital still camera. 3 and 4 show an initial state in which the shutter blade 3 fully opens the opening (exposure opening) 1a. At this time, no current is supplied to the coil 7. However, as is well known, due to the magnetic attractive force acting between the permanent magnet 12a of the rotor 12 and the magnetic rod 9, the rotor 12 has a counterclockwise rotational force in FIG. Has been granted. Therefore, as shown in FIG. 4, the shutter blade 3 is pressed against the stopper 1p and is maintained in this stopped state.

  By the way, the shutter device of the present embodiment always maintains this state by the magnetic attractive force acting between the permanent magnet 12a and the magnetic rod 9 except during photographing. Such a suction force is not absolute, and the rotor 12 may be rotated against the suction force when a strong impact is applied to the camera or a strong vibration is applied. If the rotation is slight, the rotation is restored by the above-described attraction force. However, when the rotation is greatly rotated, the attraction force acting between the magnetic rod 9 causes the rotor 12 to move to the state shown in FIG. 6 in the direction of making the state shown in FIG. 6 (in the case of this type of actuator, it is well known that such a rotational force acts). Therefore, when such a situation occurs, the shutter blade 3 is now maintained in the state of FIGS. 5 and 6.

  However, in the case of the present embodiment, since the balance plate 4 is provided, the impact force causes both the shutter blade 3 and the balance plate 4 to rotate simultaneously in the same direction, unlike the case of only the shutter blade 3. There is almost no effect. Therefore, as long as there is no excessively large force acting on the shutter blade 3 even with the balance plate 4 and the rotor 12 that are acting in different directions, the above situation may occur. Occurrence will be suppressed. When such a situation does not occur and the shutter blade 3 is fully open, the light shielding wall 12d of the rotor 12 is in the detection light path of the photosensor 10 (between the light emitting part and the light receiving part). Since the light emitted from the light emitting unit is blocked, an L level detection signal is emitted from the photosensor 10, and it is confirmed on the control circuit that the shutter blade 3 is fully opened by the detection signal. It can be confirmed.

  However, if the impact applied to the camera is so great that the shutter blade 3 is in the state of FIGS. 5 and 6 with the balance plate 4 and the rotor 12, the photo sensor Since an H level signal is emitted from 10, in that case, current is immediately supplied to the coil 7 by the signal, the rotor 12 is rotated to rotate the shutter blade 3 to the fully open position, The initial state shown in FIGS. 3 and 4 is restored. Therefore, in the present embodiment, shooting is always started from this initial state.

  When the release button is pressed at the time of shooting, the charge accumulated in the solid-state image sensor until then is released, and the accumulation of charges for shooting starts immediately after that. When a predetermined time elapses, the coil 7 is energized in the positive direction, and the rotor 12 is rotated clockwise in FIG. Therefore, the shutter blade 3 is rotated clockwise by the drive pin 12c, the balance plate 4 is rotated counterclockwise (clockwise in FIG. 4), and the opening 1a is closed by the shutter blade 3. At this time, since the light shielding wall 12d moves away from the detection optical path of the photosensor 10 due to the rotation of the rotor 12, the detection signal changes from the L level to the H level, but the detection signal from the photosensor 10 during photographing is Therefore, the operation of the shutter blade 3 is not affected at all.

  Thereafter, the shutter blade 3 abuts against the stopper 1q immediately after the opening 1a is completely closed. The shutter blade 3 is bounced by the contact, and a force is applied to reverse in the clockwise direction in FIG. Moreover, since the reversal force instantaneously surpasses the rotational force of the rotor 12, the shutter blade 3 rotates in a normal manner when the long hole 3a pushes the drive pin 12c of the rotor 12, A part of the opening 1a is temporarily opened. However, in the case of the present embodiment, the balance plate 4 is provided, and when the reversal force is applied to the shutter blade 3, the balance plate 4 is given inertia that rotates in the clockwise direction. 3 does not have the force to push back both the rotor 12 and the balance plate 4 to open the opening 1a, and stops as it is. 5 and 6 show a state in which the bounce of the shutter blade 3 is suppressed and stopped as described above.

  Thus, immediately after the closing operation of the shutter blade 3 is completed, the imaging information photoelectrically converted by the solid-state imaging device is transferred to the storage device via the image processing circuit. When the transfer is completed, the coil 7 is energized in the opposite direction. Therefore, the rotor 12 is rotated counterclockwise in FIG. 5, and the shutter blade 3 and the balance plate 4 are rotated in opposite directions by the drive pin 12c, and the shutter blade 3 rotated counterclockwise. The opening 1a is opened. Then, after the opening 1a is fully opened, the shutter blade 3 comes into contact with the stopper 1p and stops. At this time as well, the bounce of the shutter blade 3 is suppressed as described above, and one of the openings 1a. Stop without temporarily covering the part. Thereafter, when the power supply to the coil 7 is cut off, the initial state of FIG. 1 is restored.

  The above description of the operation has been made in the case where the shutter device of this embodiment is adopted in a digital still camera. However, in the case where the shutter device is adopted in a silver salt film camera, it is shown in FIGS. The closed state becomes the initial state, and at the time of photographing, the shutter blade 3 returns to the initial state after operating in the fully opened state shown in FIGS. 3 and 4.

  In the present embodiment, the shutter blade 3 is made of synthetic resin and the balance plate 4 is made of metal. This is to improve the balance of the moments of inertia of both. Therefore, it is preferable that the balance plate 4 be made of a metal having a higher specific gravity as the balance plate 4 is made thinner. However, when considering such a balance, in addition to the weight comparison with the shutter blades 3, other factors such as the rotational force of the rotor 12 are also involved, so the materials of the shutter blades 3 and the balance plate 4 are related. Is not limited to the case of this embodiment. In this embodiment, a current control type actuator called a moving magnet type motor or the like is used as the drive means, and the drive pin is integrally formed with the rotor. The means is not limited to such a configuration, and the drive source may be another electromagnetic actuator such as a step motor or a spring, and the drive pin is not integral with the rotor. It may be provided on a member that is reciprocated by a drive source.

  Furthermore, if the shutter blade 3 of this embodiment is replaced with the already described diaphragm blade, filter blade, and barrier blade, an effective diaphragm device, filter device, and lens barrier device can be obtained. Therefore, the present invention can also be applied to those blade driving devices.

It is the front view of the Example which showed the shutter blade fully open state. Although it is principal part sectional drawing of FIG. 1, the shutter blade | wing is shown in the closed state. It is a front view of the Example shown in the state which removed the flexible printed wiring board from FIG. FIG. 4 is a rear view of FIG. 3. It is the front view which showed the closed state of the shutter blade | wing similarly to FIG. FIG. 6 is a rear view of FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ground plate 1a, 2a Opening part 1b, 1c, 1d, 1e, 1f, 1m, 1n Axis 1g, 1h, 2b, 2c, 2d, 11a, 11b Hole 1i, 1j, 1k receiving part 1p, 1q stopper 1r, 2e, 3a, 4a long hole 1s hook part 1t, 1u, 5a, 6b positioning pin 2 cover plate 3 shutter blade 4 balance plate 5 first stator frame 6 second stator frame 6a, 10a terminal pin 7 coil 8 yoke 9 magnetic body Bar 10 Photosensor 11 Flexible printed circuit board 12 Rotor 12a Permanent magnet 12b Arm 12c Drive pin 12d Light-shielding wall

Claims (3)

  A base plate having an opening for a photographing optical path and two stoppers, and is attached to the base plate so as to be rotatable and has a long hole in the vicinity of the mounting portion, and the reciprocating rotation makes the opening. One blade that advances and retreats to the part, a balance plate that is rotatably attached to the base plate and has a long hole in the vicinity of the attachment part, a long hole of the blade, and a long hole of the balance plate Drive means inserted into both of them, and by reciprocating the drive pins, the blades and the balance plate are rotated in opposite directions so that only the blades are advanced and retracted into the opening, The camera blade drive device according to claim 1, wherein the blade is brought into contact with each stopper and stopped when the blade enters the opening and when the blade leaves the opening.   The camera blade drive device according to claim 1, wherein the blades are made of synthetic resin, the balance plate is made of metal, and both have substantially the same weight.   The drive means is a motor comprising a stator having a coil and a rotor having a permanent magnet, and the drive pin is an output pin that reciprocally rotates in a predetermined angular range integrally with the rotor; 4. The rotor according to claim 1, wherein a rotational force is applied to the rotor in a direction in which the blade comes into contact with the stopper by the magnetic force of the permanent magnet when the coil is not energized. 5. The blade drive device for a camera described.