JP6071268B2 - Shutter device and imaging device including the same - Google Patents

Description

  The present invention relates to a shutter device and an imaging device including the shutter device.

  In a digital single-lens reflex camera with interchangeable lenses, a shutter device is disposed in the vicinity of an image sensor.

  Patent Document 1 proposes a single-lens reflex type imaging apparatus that performs an imaging operation using an electronic front curtain and a rear curtain of a mechanical shutter. In this imaging apparatus, imaging is performed by starting accumulation of the imaging element by an electronic shutter function of the imaging element and driving a blade group constituted by a mechanical shutter to shield the imaging element.

  In general, a blade group of a mechanical shutter is rotatably held by two arms to form a parallel link. The rear drive member transmits a driving force such as a spring to the blade group via the arm, and causes the blade group to travel.

JP 2008-299089 A

  However, in the configuration of Patent Document 1, the rear drive member is connected to the arm farther from the first blade, which is the tip in the traveling direction, out of the two arms of the parallel link.

  For this reason, the leading end surface of the first blade in the traveling direction is unstable in the optical axis direction (blade thickness direction), and blurring occurs during traveling, resulting in an increase in variation in exposure amount that results in shutter accuracy.

  Further, since the rear drive member is disposed at a position away from the optical axis, the shutter device is increased in size.

  In view of such a problem, an object of the present invention is to stabilize the shutter accuracy and reduce the size of the shutter device.

A shutter device according to one aspect of the present invention includes a shutter base plate in which an opening for exposure is formed, a blade group that forms an opening region of the opening by an opening forming end that is a tip in a traveling direction, and the blade group A blade arm member arranged in the order of the first arm and the second arm from the opening forming end side along the traveling direction of the blade group, and a drive connected to the first arm A blade driving member that includes a pin and rotates the first arm by driving the driving pin; and a driving force from the motor is supplied to the blade driving member via a charge member that charges the blade driving member. The blade drive member is closer to the center of the opening than the charge member when viewed from a direction parallel to the pivot axis of the arm, From transmission member Characterized in that it is arranged in the distance.

  According to the present invention, the shutter accuracy can be stabilized and the shutter device can be downsized.

1 is an external perspective view of an imaging apparatus equipped with a focal plane shutter that is an example of an embodiment of a shutter device of the present invention. It is a block diagram of an imaging device. It is a disassembled perspective view of a focal plane shutter. It is a rear view of a focal plane shutter. It is a front view of a cam gear. 3 is an exploded perspective view of a charge lever 260. FIG. It is an enlarged view of a blade drive member. It is a disassembled perspective view of a blade drive member. It is sectional drawing of the axis | shaft of a shutter base plate. It is a perspective view of an auxiliary ground plane. It is a rear view of a focal plane shutter with a flexible substrate attached. It is the sectional view on the AA line of FIG. It is the figure which expanded a part of focal plane shutter. It is AA sectional view taken on the line of FIG. It is the perspective view which showed the state just before attaching a buffer member to a shutter base plate. It is the figure which looked at the electromagnet from the adsorption | suction surface of the yoke. It is an operation | movement figure of the blade group of a focal plane shutter. It is a figure which shows the operation timing of a focal plane shutter and an image pick-up element.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an external perspective view of an imaging apparatus equipped with a focal plane shutter which is an example of an embodiment of a shutter apparatus according to the present invention.

  On the upper surface of the imaging apparatus 100, an accessory shoe 140 for attaching a photographing accessory such as a power button 110, a release button 130, and a flash device is provided. The lens mount 150 is an attachment portion for a photographing lens (not shown).

  Since the imaging apparatus 100 is a mirrorless type imaging apparatus having no reflex mirror, the shutter curtain is opened in a shooting standby state for live view display. Therefore, as shown in FIG. 1, the image pickup surface of the image pickup device 3 is exposed in a state where the photographing lens is removed.

  FIG. 2 is a block diagram of the imaging apparatus 100.

  The focal plane shutter (shutter device) 2 is provided between the imaging lens 1 and the imaging element 3 on the imaging optical path, and adjusts the exposure time of the imaging element 3 in conjunction with the electronic front curtain operation of the imaging element 3. .

  The image sensor 3 uses a CMOS image sensor or the like, and photoelectrically converts a subject image formed by the imaging lens 1 that forms light from the subject. The analog image signal output from the image sensor 3 is converted into a digital signal by an AFE (Analog Front End) 4. The digital image signal output from the AFE 4 is subjected to various image processing, compression / decompression processing, and the like by a DSP (Digital Signal Processor) 5.

  The recording medium 6 records image data processed by the DSP 5. The display unit 7 uses a liquid crystal display (LCD) or the like, and displays captured images and various menu screens.

  The image sensor driving circuit 8 controls driving of the image sensor 3. The RAM 10 is connected to the DSP 5 and temporarily stores image data and the like. The shutter drive circuit 11 drives the focal plane shutter 2.

  A CPU 9 controls the AFE 4, the DSP 5, the image sensor driving circuit, and the shutter driving circuit 11.

  Reference numeral 91 denotes voltage detection means for detecting the power supply voltage of the image pickup apparatus 100, reference numeral 92 denotes temperature detection means for detecting the temperature of the image pickup apparatus, and reference numeral 93 denotes phase detection means provided in the focal plane shutter 2. It is comprised from a cam phase detection means. A lens control unit 94 outputs lens information such as a focal length, an aperture diameter, a pupil diameter, and a distance between the pupil and the imaging element of the imaging lens 1 to the CPU 9 and drives the aperture, the lens, and the like according to control by the CPU 9. . The detection result of each detection means is input to the CPU 9.

  FIG. 3 is an exploded perspective view of the focal plane shutter 2. 3A is an exploded perspective view of the focal plane shutter 2 as viewed from the side where the imaging device 3 is attached (hereinafter referred to as the back), and FIG. 3B is the side where the imaging lens is attached (hereinafter referred to as front). It is the disassembled perspective view seen from. FIG. 4 is a rear view of the focal plane shutter 2. The auxiliary ground plate 205 and the cover plate 206 are omitted for easy viewing of the drawing.

  The shutter base plate 201 is fixed inside the imaging apparatus 100, and each component constituting the driving mechanism of the blade group 230 is attached.

  The motor 220 is attached to the shutter base plate 201 so that the output axis is substantially parallel to the imaging optical axis (the optical axis of the light beam passing through the opening 206a). The cam gear 203 is rotated by a driving force transmitted from the motor 220 via a reduction gear train that is a transmission member.

  The blade driving member 202, the cam gear 203, and the charge lever 260 are rotatably supported on the shutter base plate 201, respectively.

  In the present embodiment, the driving force of the cam gear 203 is transmitted to the blade driving member 202 via the charge lever 260, whereby the charging operation and the releasing operation of the focal plane shutter 2 are performed.

  FIG. 5 is a front view of the cam gear. A cam portion 203 a is formed on one surface of the cam gear 203. As shown in FIG. 5, the cam portion 203a is divided into four regions, a cam top region 203a-1, a cam inclined region 203a-2, a cam bottom region 203a-3, and a charge region 203a-4. Further, the flange portion 203 d of the cam gear 203 is formed so as to protrude from the cam surface of the cam portion 203 a toward the outer periphery of the cam gear 203.

  FIG. 6 is an exploded perspective view of the charge lever 260. As shown in FIG. 6, the charge lever 260 has a shaft portion 260 a extending and a contact portion 260 b. A charge roller (second charge roller) 204b is attached to the shaft portion 260a. The contact portion 260b contacts a charge roller (first charge roller) 204a provided on the blade driving member 202. The cam gear 203 drives the charge lever 260 by always tracing the cam portion 203a of the cam gear 203 by the 204b attached to the shaft portion 260a.

  The charge roller 204b has a sizing shape for adjusting the overcharge amount, and is replaced when the overcharge amount of the focal plane shutter 2 is out of a predetermined range. That is, a plurality of types of charge rollers 204b having different outer diameters are prepared, and the charge roller 204b having the optimum outer diameter is selected from the plurality of types of charge rollers 204b so that the overcharge amount falls within a predetermined range. .

  Further, as shown in FIG. 4, the cam gear 203 is disposed so that the charge roller 204 b and the flange portion 203 d overlap in the extending direction of the shaft portion 260 a of the charge lever 260. Since the flange portion 203 d is formed over the entire circumference of the cam gear 203, the charge roller 204 b always overlaps with the flange portion 203 d of the cam gear 203. With this configuration, the charge roller 204b can be replaced by simply removing the cam gear 203 without falling off the shaft portion 260a without attaching a retaining member such as a clip. Therefore, the number of man-hours for exchanging the charge roller 204b is reduced, and the amount of rotation of the charge lever 260 can be easily adjusted.

  FIG. 7 is an enlarged view of the blade driving member 202, and FIG. 8 is an exploded perspective view of the blade driving member 202.

  When the charge lever 260 rotates the blade driving member 202, the contact portion 260 b contacts the charge roller 204 a provided on the blade driving member 202. As a result, the charge lever 260 reciprocates. A charge lever return spring (not shown) is attached to the charge lever 260 so as to bias the charge lever 260 and the blade driving member 202 in a direction away from each other.

  The charge roller cover 214 is flexible and has a U-shaped cross section. Further, the charge roller cover 214 has a first hole 214a and a second hole 214b. The first hole 214a and the second hole 214b are formed at positions that are point-symmetric with each other.

  Before attaching the charge roller cover 214 to the blade driving member 202, the charge roller 204 a is attached to the shaft portion 202 g that is formed to extend to the blade driving member 202.

  The first hole 214a of the charge roller cover 214 is engaged with the first protrusion 202e formed at the tip of the shaft portion 202g. While the charge roller cover 214 is elastically deformed, the second hole 214 b of the charge roller cover 214 is engaged with the second protrusion 202 f provided on the blade driving member 202. As a result, the charge roller cover 214 is attached to the blade driving member 202. By attaching the charge roller cover 214 to the blade driving member 202, the charge roller 204a is held so as not to come off from the first protrusion 202e. That is, the charge roller cover 214 functions as a retaining member that prevents the charge roller 204a pivotally supported by the shaft portion 202g from coming off the shaft portion 202g.

  The charge roller 204a contacts the contact portion 260b of the charge lever 260 and is held by the charge roller cover 214 to the extent that the charge roller 204a can rotate.

  The second projecting portion 202f is formed to project in the direction opposite to the extending direction of the shaft portion 202g. The first protrusion 202e and the second protrusion 202f are formed on different axes. The first protrusion 202e and the second protrusion 202f are formed at positions that are point-symmetric with respect to each other. Therefore, when the charge roller cover 214 is attached to the blade driving member 202, the second hole 214b is engaged with the first protrusion 202e, and the first hole 214a is engaged with the second protrusion 202f. Also good.

  The first protrusion 202e and the second protrusion 202f are formed on different axes. For this reason, once the charge roller cover 214 is attached to the blade driving member 202, the charge roller cover 214 does not rotate around the first protrusion 202e, nor does it rotate around the first protrusion 202e. Thereby, since the charge roller 204a can be positioned, it is possible to improve assemblability.

  Further, since the charge roller 204a is attached to the blade driving member 202 regardless of the blade driving spring, the accuracy of the blade traveling operation is not affected. As described above, in this embodiment, the charge roller 204a is not a part that is replaced for adjustment because the overcharge amount is adjusted by replacing the charge roller 204b. Since the inertia of the blade driving member 202 does not change by adjustment and is always constant, the traveling characteristics of the blade group 230 are stabilized.

  Further, in the present embodiment, the distance between the central axis of the first protrusion 202e and the central axis of the second protrusion 202f is equal to the central axis of the fitting part 202d of the blade driving member 202 and the first protrusion 202e. It is shorter than the distance from the central axis. As a result, the focal plane shutter 2 can be made smaller than before.

  In general, in a configuration in which the blade drive member is charged and released by the cam gear, the cam gear must be disposed at a position away from the optical axis in order to avoid collision between the cam gear and the blade drive member. Therefore, it is necessary to increase the size of the cam gear and to rotate the cam gear once, which causes a problem that the shutter unit is increased in size.

  On the other hand, in the present embodiment, the charge lever 260 is disposed on the side farther from the optical axis (the center of the opening 201p) than the blade driving member 202 in the horizontal direction. The cam gear 203 is disposed closer to the optical axis (center of the opening 201p) than the blade driving member 202 in the horizontal direction. The charge lever 260 charges the blade driving member 202 by reciprocating motion. Therefore, the focal plane shutter 2 can be reduced in size.

  Furthermore, in this embodiment, the distance from the rotation center of the charge lever 260 to the contact portion with the charge roller 204a is made longer than the distance from the rotation center of the charge lever 260 to the contact portion with the charge roller 204b. Yes. Accordingly, the charge amount of the cam gear 203 can be amplified to charge the blade driving member 202, and the reciprocating range of the charge lever 260 can be reduced. As a result, the focal plane shutter 2 can be reduced in size.

  The auxiliary base plate 205 is engaged with and attached to the tips of the shafts 201a, 201b, 201c, 201d, and 201e of the shutter base plate 201. A holding electromagnet 250 is fixed to the auxiliary ground plate 205 with screws 255.

  The cover plate 206 is fixed to the shutter base plate 201 on the same side as the auxiliary base plate 205. At the center of the cover plate 206, an opening 206a is formed at a position corresponding to the opening 201p for exposure of the shutter base plate 201 when assembled.

  A blade chamber in which a blade group 230 attached to the blade driving member 202 is disposed is formed between the shutter base plate 201 and the cover plate 206.

  The blade group 230 includes a first blade 231, a second blade 232, a third blade 233, and a fourth blade 234. The tip of the first blade 231 in the traveling direction (hereinafter referred to as an opening forming end) forms an opening region of the opening 201p formed in the shutter base plate 201.

  Each blade is made of a metal plate coated with black paint and is rotatably supported by a main arm (first arm) 235 and a sub arm (second arm) 236 which are blade arm members to form a parallel link. doing.

  The main arm 235 and the sub arm 236 are disposed in order from the opening forming end side of the first blade 231 along the traveling direction of the blade group 230.

  FIG. 9 is a cross-sectional view of the shaft 201 a of the shutter base plate 201. As illustrated in FIG. 9, the blade driving member 202 is pivotally supported by the shaft 201 a of the shutter base plate 201 by inserting the shaft 201 a of the shutter base plate 201 into the shaft support portion 202 d of the blade driving member 202.

  The hole 235b of the main arm 235 is fitted to the outer periphery of the shaft support 202d of the blade driving member 202 on the surface of the shutter base plate 201 on the blade chamber side. In the present embodiment, the main arm 235 and the blade driving member 202 are both disposed on the same surface side of the shutter base plate 201 and rotate around the shaft 201 a of the shutter base plate 201.

  A driving pin 202 a is formed at the tip of the blade driving member 202, and the driving pin 202 a is connected to a hole 235 a formed in the main arm 235 and passes through a long hole portion 201 g formed in the shutter base plate 201. Yes.

  When the driving pin 202a is moved along the long hole portion 201g by the rotation of the blade driving member 202, the main arm 235 rotates around the rotation hole portion 235b, and accordingly the blade group 230 is opened and closed. When the blade group 230 operates, the opening 201p can be in an open state (a state in which a light beam passes) or in a light-shielding state (a state in which the light beam is blocked).

  Since the blade group 230 rotates together with the main arm 235 and the blade driving member 202 only by being fitted to the main arm 235, the sliding friction generated in the blade group 230 is reduced.

  The sub arm 236 is rotatably supported by a shaft 201 f provided on the shutter base plate 201, and a blade backlash spring is hung in a direction in which the blade group 230 travels.

  The ratchet gear 240 is rotatably supported on the shaft 201 a of the shutter base plate 201 and is disposed on the shaft tip side from the blade driving member 202. The ratchet gear 240 is engaged with a ratchet claw formed on the shutter base plate 201.

  Between the blade driving member 202 and the ratchet gear 240, a blade driving spring (elastic member) (not shown) that is a torsion coil spring is disposed. One end of the blade driving spring is hooked on the blade driving member 202, and the other end is hooked on the ratchet gear 240. The spring force of the blade drive spring is adjusted by changing the engagement position between the ratchet gear 240 and the ratchet pawl. The blade drive spring 241 urges the blade drive member 202 in the clockwise direction in FIG.

  A first photo interrupter 207 a and a second photo interrupter 207 b as non-contact type phase detection means are attached to the auxiliary ground plane 205. The first photo interrupter 207a corresponds to the first optical detection means, and the second photo interrupter 207b corresponds to the second optical detection means.

  The blade driving member 202 is formed with a detected portion 202c, and the first photo interrupter 207a and the detected portion 202c constitute blade phase detecting means.

  The detected portion 202c is provided so that the detected portion 202c shields the first photo interrupter 207a when the blade driving member 202 is located at the charge completion position. Therefore, when the blade driving member 202 is at the charge completion position, the detected portion 202c shields the first photo interrupter 207a. At this time, the first photo interrupter 207a outputs an H signal. Similarly, the detected portion 202c is provided so that the detected portion 202c does not shield the first photo interrupter 207a when the blade driving member 202 is located at the travel completion position. Therefore, when the blade driving member 202 is at the travel completion position, the detected portion 202c does not shield the first photo interrupter 207a. At this time, the first photo interrupter 207a outputs an L signal.

  The cam gear 203 has a detected portion 203e on the surface opposite to the surface on which the cam portion 203a is formed. The second photo interrupter 207b and the detected portion 203e constitute cam phase detecting means.

  When the charge roller 204b traces the cam top region 203a-1 of the cam portion 203a, the detected portion 203e shields the second photo interrupter 207b. At this time, the second photo interrupter 207b outputs an H signal. When the charge roller 204b traces the cam bottom region 203a-3 of the cam portion 203a, the detected portion 203e shields the second photo interrupter 207b. At this time, the second photo interrupter 207b outputs an L signal. The state where the charge roller 204b traces the cam top region 203a-1 of the cam portion 203a is referred to as the cam gear 203 being in the cam top phase. The state where the charge roller 204b traces the cam bottom region 203a-3 of the cam portion 203a is referred to as the cam gear 203 being in the cam bottom phase.

  Here, the configuration of the cam phase detecting means constituted by the second photo interrupter 207b and the detected part 203e will be described.

  FIG. 10 is a perspective view of the auxiliary ground plane 205 with the flexible substrate 270 attached thereto. FIG. 10A is a front view, and FIG. 10B is a rear view. FIG. 11 is a rear view of the focal plane shutter 2 with the flexible substrate 270 attached thereto. 12 is a cross-sectional view taken along line AA in FIG.

  As shown in FIG. 12, a shaft 201 c formed on the shutter base plate 201 is a rotation center shaft of the cam gear 203 and is engaged with the auxiliary base plate 205. A flexible substrate 270 is attached to the auxiliary ground plate 205.

  Since the second photo interrupter 207b is attached to the flexible substrate 270, the second photo interrupter 207b is disposed between the surface of the flexible substrate 270 and the cam gear 203 on which the detected portion 203 is formed. Depending on the position of the detected part 203, the position where the second photo interrupter 207b is installed changes, and the wiring of the flexible substrate 270 also changes.

  In the present embodiment, since the detected portion 203e is erected in the same direction as the protruding direction of the shaft 201c, the configuration shown in FIG. 12 is obtained, and the second photo interrupter 207b is provided near the shaft of the cam gear 203. Can be arranged. At this time, as shown in FIG. 10, since the wiring of the flexible substrate 270 can be simplified, the focal plane shutter 2 can be reduced in size.

  Further, in the present embodiment, unlike contact type phase detection means such as a brush, there is no detection deterioration due to dust or oil or aging deterioration such as flex pattern scraping due to chattering and the like, so that reliability is improved. .

  By the way, when the photo interrupter for detecting that the cam gear 203 is in the cam top phase and the photo interrupter for detecting that the cam gear 203 is in the cam bottom phase are provided separately, two detected positions at different positions in the radial direction on the cam gear 203 are provided. It is necessary to provide a part. However, in this case, the diameter of the cam gear 203 becomes extremely large.

  In the present embodiment, one photo interrupter detects that the cam gear 203 is in the cam top phase and that the cam gear 203 is in the cam bottom phase. As a result, the detected portion that detects that the cam gear 203 is in the cam top phase and the detected portion that detects that the cam gear 203 is in the cam bottom phase are arranged side by side on the same circumference of the cam gear 203. Thus, the outer diameter of the cam gear 203 is not increased. Further, since the detected portion 203e is disposed closer to the rotation center than the cam surface of the cam portion 203a, the focal plane shutter 2 can be reduced in size. Further, the blade driving member 202 is reciprocating, and the focal plane shutter 2 is enlarged only for the travel locus of the detected portion 202c. Furthermore, the detected portion 202c has a higher degree of design freedom than providing another detected portion on the cam gear 203 that rotates, and can be arranged according to the space in the imaging device 100. This also contributes to the downsizing.

  FIG. 13 is an enlarged view of a part of the rear view of the focal plane shutter 2. FIG. 14 is a cross-sectional view taken along line AA in FIG. 13, with the upper side representing the blade chamber outer side and the lower side representing the blade chamber side. FIG. 15 is a perspective view of the state in which the buffer member 242 is attached to the shutter base plate 201 as viewed from the inside of the blade chamber.

  The buffer member 242 is formed of a material such as rubber and is attached to the end of the long hole portion 201g of the shutter base plate 201. When the blade driving member 202 collides with the buffer member 242 on a surface perpendicular to the traveling direction of the drive pin 202a when the exposure is completed, the buffer member 242 absorbs an impact when the blade driving member 202 stops suddenly. Therefore, the buffer member 242 can improve the durability of the blade driving member 202 and can suppress the bounce when the driving is completed.

  The elongated hole portion 201g is formed with a first convex portion 201h and a pair of concave portions (second concave portions) 201i on the outer side of the blade chamber along a circular arc-shaped edge, and a pair of concave portions (second concave portion ( A first concave portion 201j is formed.

  The buffer member 242 has a concave portion (third concave portion) 242h formed outside the blade chamber, a pair of convex portions (third convex portion) 242i and a pair of convex portions (second convex portion) 242j inside the blade chamber. Is formed.

  Here, a method of attaching the buffer member 242 to the long hole portion 201g of the shutter base plate 201 will be described.

  First, the concave portion 242h of the buffer member 242 is inserted below the convex portion 201h of the shutter base plate 201. At this time, the pair of convex portions 242j of the buffer member 242 are positioned on the pair of tapered surfaces 201k formed on the shutter base plate 201.

  Next, the buffer member 242 is deformed and inserted so that the pair of convex portions 242j of the buffer member 242 fit into the pair of concave portions 201j of the shutter base plate 201.

  After the buffer member 242 is attached to the end of the long hole portion 201g of the shutter base plate 201, a restoring force acts on the buffer member 242. For this reason, the concave portion 242h, the pair of convex portions 201i, and the pair of convex portions 201j of the buffer member abut on the convex portion 201h, the concave portion 201i, and the concave portion 201j of the shutter base plate 201, respectively.

  At this time, as shown in FIG. 14, the buffer member 242 is disposed within the thickness of the shutter base plate 201 and does not protrude outside the blade chamber of the shutter base plate 201. Therefore, the buffer member 242 does not interfere with other components attached to the shutter base plate 201, and is not subject to design restrictions.

  With such a configuration, the buffer member 242 is suitably attached to the long hole portion 201g formed in the shutter base plate 201, and even if vertical vibration is applied to the buffer member 242, the buffer member 242 is within the thickness of the shutter base plate 201. Be placed.

  As shown in FIG. 13, the buffer member 242 is a distance L between a portion 242 m that is the contact portion between the drive pin 202 a and the buffer member 242 and is closest to the shutter base plate 201 and the tip 201 m of the first convex portion 201 h. Is larger than the length R of the drive pin 202a in the mounting direction.

  Thereby, since the intensity | strength of the buffer member 242 can be strengthened more, durability can be improved.

  FIG. 16 is a view of the holding electromagnet 250 as viewed from the attracting surfaces 251 a and 251 b of the yoke 251.

  The yoke 251 has a substantially U shape having a first leg and a second leg. A bobbin 252 around which a coil 253 is wound is provided on the first leg.

  Terminal pins 254 a and 254 b connected to both ends of the coil 253 are formed on the bobbin 252.

  The blade driving member 202 is provided with an armature support portion 202b shown in FIG. A through-hole portion (not shown) formed in the armature support portion 202 b is engaged with an armature shaft that extends in a direction substantially orthogonal to the suction surface of the armature 212 and is integrally attached to the armature 212. . A compression spring (not shown) is disposed on the outer periphery of the armature shaft, and biases the armature 212 and the armature support portion 202b in a direction away from each other.

  When a voltage is applied between the terminal pins 254a and 254b, the coil 253 generates a magnetic flux.

  At this time, the suction surface 251 a of the first leg and the suction surface 251 b of the second leg function as a suction surface with the armature 212.

  In the magnetic circuit formed by the yoke 251 and the armature 212 in this embodiment, the sectional area of the armature 212 is the smallest. Therefore, the magnetic flux generated in the magnetic circuit is determined by the amount by which the magnetic flux density in the cross section of the armature 212 is saturated.

  In this embodiment, the armature 212 is designed to have such a size that the rigidity, strength, etc. are not too weak while reducing the moment of inertia of the blade driving member 202.

Usually, a magnetic flux leaking into the air exists in the magnetic circuit. Since it is closer to the coil 253 that is the magnetic flux generation source than the armature 212, the magnetic flux amount Φ _Y1 generated on the attracting surface 251a of the yoke 251 is larger than the magnetic flux amount Φ _A generated on the cross section of the armature 212.

On the other hand, the amount of magnetic flux Φ _Y2 generated on the attracting surface 251b of the yoke 251 that is farther from the coil 253 that is the magnetic flux generation source than the armature 212 is smaller than the amount of magnetic flux Φ _A generated in the cross section of the armature 212.

  The magnetic attracting force acting on each attracting surface of the yoke 251 can be expressed using the following equation.

  Here, F is the attractive force acting on the attracting surface, μ is the magnetic permeability, B is the magnetic flux density of the attracting surface, S is the area of the attracting surface, and Φ is the amount of magnetic flux.

As described above, the amount of magnetic flux generated on the suction surface 251a and the suction surface 251b is Φ _Y1 > Φ _Y2 . Therefore, in the present embodiment, the area of the suction surface 251b is adjusted to be smaller than the area of the suction surface 251a so that the suction force generated on each surface becomes equal. Therefore, when the exposure is started after the energization to the coil is stopped, the armature 212 can be simultaneously separated from the suction surface 251a and the suction surface 251b.

  Therefore, the time until the driving member is driven is constant, and variations in exposure time can be suppressed.

  Note that at least one of the armature 212 and the yoke 251 is made of a permalloy alloy.

  The imaging operation of this embodiment will be described with reference to FIGS. 17 and 18.

  FIG. 17 is an operation diagram of the blade group 230 of the focal plane shutter 2. In FIG. 17, the auxiliary ground plate 205 and the cover plate 206 are omitted for easy viewing of the drawing. FIG. 18 is a diagram illustrating the operation timing of each component of the focal plane shutter 2 and the image sensor 3. In addition, (1)-(10) in FIG. 18 respond | corresponds to each operation state.

  FIG. 17A shows an overcharge state of the blade driving member 202, that is, a state where the imaging device 100 is stopped and a live view state. FIG. 17B shows a standby state before traveling of the blade group 230, and FIG. 17C shows a traveling completion state of the blade group 230. FIG. 17D shows a state where the opening forming end 231a of the first blade 231 in the middle of the exposure control operation from the state shown in FIG. 17A to the state shown in FIG. .

  In FIG. 18A, the focal plane shutter 2 is in an overcharged state as shown in FIG. 17A, and the blade group 230 is superimposed, so that the light flux is allowed to pass through.

  In the imaging apparatus 100, a live view imaging operation is performed, and a subject image incident on the imaging element 3 is displayed on an image display unit (not shown). At this time, the CPU 9 checks whether each of the first photo interrupter 207a and the second photo interrupter 207b outputs an H signal. That is, it is confirmed that the blade driving member 202 is in a charge complete state and the cam gear 203 is in the cam top phase. When the first photo interrupter 207a or the second photo interrupter 207b outputs the L signal, the CPU 9 instructs the shutter drive circuit 11 to energize the motor 220. The shutter drive circuit 11 energizes the motor 220 until the first photo interrupter 207a and the second photo interrupter 207b each output an H signal.

  In this embodiment, since the phase of the cam gear 203 is detected by an output from one photo interrupter, an H signal is output regardless of whether the cam gear 203 is in the cam top phase or the cam bottom phase. At this time, when it is detected from the output from the first photo interrupter 207a that the blade driving member 202 is in the charging completed state, the phase detecting means 93 can detect that the cam gear 203 is in the cam top phase.

  When the release operation is started (FIG. 18B), the CPU 9 controls the shutter drive circuit 11, so that the shutter drive circuit 11 energizes the coil 253, generates a magnetic force in the yoke 251, and connects the yoke 251 and the armature 212. Set to adsorption state.

  After the yoke 251 and the armature 212 are attracted, the shutter drive circuit 11 energizes the motor 220 to rotate the cam gear 203 counterclockwise. The charge roller 204a moves from the state of tracing the cam top region 203a-1 of the cam gear 203 to the state of tracing the cam inclined region 203a-2. The charge lever 260 is gradually released from the overcharge state by tracing the cam inclined region 203a-2. When the charge roller 204a enters the state of tracing the cam bottom region 203a-3, the state shifts to the standby state before traveling of the blade group 230 shown in FIG. Then, when the second photo interrupter 207b changes from the state of outputting the L signal to the state of outputting H, the shutter drive circuit 11 stops energizing the motor 220 ((3) in FIG. 18).

When the CPU 9 controls the image sensor drive circuit 8, the image sensor drive circuit 8 resets all the pixels of the image sensor 3 (FIG. 18 (4)). Thereafter, the CPU 9 controls the image sensor driving circuit 8 so that the image sensor driving circuit 8 starts electronic front curtain scanning (FIG. 18 (5)). In the period from FIG. 18 (4) to FIG. 18 (5), the all-pixel reset state of the image sensor 3 is continued.
Here, the electronic front curtain scanning refers to starting charge accumulation line by line with respect to the image sensor 3 in which all pixels are in a reset state. Since the scanning pattern for starting charge accumulation line by line is a scanning pattern that matches the running characteristics of the blade group 230, the uniform accumulation time (exposure time) is obtained for any line of the image sensor 3. The CPU 9 controls the shutter drive circuit 11 so that after the electronic front curtain scan is started, the shutter drive circuit 11 turns off the coil 253 after a time interval corresponding to the set shutter time. As a result, the attractive force acting between the yoke 251 and the armature 212 disappears (FIG. 18 (6)). The blade driving member 202 starts to rotate in the clockwise direction by the bias of the torsion coil spring. At this time, as described above, since the suction forces acting on the two suction surfaces of the yoke 251 and the armature 212 are equal, the two suction surfaces of the yoke 251 and the armature 212 are separated from each other almost simultaneously. Thereby, the dispersion | variation in the drive timing of the blade drive member 202 when the electricity supply to the coil 253 is cut off is reduced.

  At this time, in the exposure process from the state of FIG. 17A to the state of FIG. 17C, the driving force is transmitted to the first blade 231 via the driving force transmitted portion 235 c of the main arm 235. Since the driving force transmitted portion 235c is provided at a position preceding the center of gravity of the first blade 231 in the exposure direction, the first blade 231 operates by being pulled by the main arm 235.

  When the blade driving member 202 is rotated via the driving force transmitted portion 235c of the main arm 235, the opening forming end 231a can travel stably without being shaken in the optical axis direction.

  Further, since the first blade 231 operates by pulling the sub arm 236, the sub arm 236 operates while being pulled by the main arm 235.

  The second blade 232, the third blade 233, and the fourth blade 234 are sequentially operated in the same manner as the first blade 231 and pull the main arm 235 and the sub arm 236. As for the operation amount, the first blade 231 is the largest, and the operation amount decreases in the order of the second blade 232, the third blade 233, and the fourth blade 234.

  In the present embodiment, the hole 235 a of the main arm 235 is formed on a substantially straight line connecting the center of the shaft 201 a that is the rotation center of the main arm 235 and the shaft support center of the first blade 231. Therefore, as indicated by an arrow in FIG. 17D, the rotation normal direction of the portion where the main arm 235 and the first blade 231 are pivotally supported, that is, the traveling direction of the blade group 230, and the driving pin of the blade driving member 202. The normal direction at the center of the rotation locus of 202a is substantially the same. Accordingly, the state in which the opening 201p illustrated in FIG. 17D is half-shielded can transmit the driving force of the blade driving member 202 to the first blade 231 most efficiently.

  With such a configuration, the driving force transmission efficiency of the blade driving member 202 is substantially the same between the state in which the blade group 230 starts to travel and the state in which the blade group 230 completes traveling, and the traveling characteristics are stabilized. be able to.

  In the present embodiment, the blade driving member 202 and the main arm 235 are separate members. However, the blade drive member 202 and the main arm 235 are integrated by fastening, heat welding, integral molding such as mold insert / outsert, etc., and at least one fixing portion is provided at the position of the drive pin 202a. Also good.

  As the blade drive member 202 travels, the drive pin 202a comes into contact with the contact portion (first contact portion) 242a. After that, when the drive pin 202a further travels while compressing the buffer member 242, as shown in FIG. 14, the main arm 235 collides with the contact portion (second contact portion) 242b, and the impact is absorbed and stopped. To do. In this way, the blade driving member 202 and the main arm 235 are effectively absorbed by the two contact portions 242a and 242b of the buffer member 242, respectively, and the exposure of the blade group 230 is completed. Thereby, the opening 201p of the shutter base plate 201 is in a state where the light beam is blocked as shown in FIG. 17C (FIG. 18B).

  When the traveling of the blade group 230 of the focal plane shutter 2 is finished and the image sensor 3 is completely shielded from light, the CPU 9 controls the image sensor drive circuit 8 so that the image sensor drive circuit 8 starts the still image reading scan. To do. At this time, the CPU 9 checks whether the first photo interrupter 207a and the second photo interrupter 207b each output an L signal. That is, it is confirmed that the blade driving member 202 is in the travel completion state and the cam gear 203 is in the cam bottom phase. If the first photo interrupter 207a or the second photo interrupter 207b outputs an H signal, an abnormal state of the blade group 230, the blade driving member 202, or the like is suspected, so the imaging operation is stopped and the display unit 7 Displays an error.

  The area where the charge reading of the image sensor 3 is not completed needs to be in a state where the light beam is blocked.

  The CPU 9 controls the shutter drive circuit 11 after a predetermined time has elapsed from the start of reading the charge of the image sensor 3 (FIG. 18 (8)), whereby the shutter drive circuit 11 energizes the motor 220 and turns the cam gear 203 counterclockwise. Rotate in the direction. As a result, the blade driving member 202 rotates clockwise against the urging force of the torsion coil spring to perform a charging operation. At this time, the blade group 230 is gradually overlapped, and the opening 201p is sequentially opened from the line where the charge reading of the image sensor 3 is completed. That is, in the present embodiment, the opening 201p starts to be opened before the reading of the charges of all the pixels is completed. At this time, the charge start timing is set so that the light leaking from the portion where the blade group 230 is opened does not enter the pixels in the row where the still image readout scanning has not yet reached.

  After the charge readout of all the pixels of the image sensor 3 is completed (FIG. 18 (9)), the blade group 230 is completed and the opening 201p is opened. Then, the second photo interrupter 207b changes from the state of outputting the L signal to the state of outputting the H signal, and the shutter drive circuit 11 stops energizing the motor 220 (FIG. 18 (10)), FIG. 18 (a). . As a result, the blade driving member 202 is overcharged again.

  When the charging operation ends, the CPU 9 starts a live view imaging operation for the electronic viewfinder function.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

2 focal plane shutter 100 imaging device 201 shutter base plate 201p opening 202 blade driving member 202a driving pin 203 cam gear 231a opening forming end 235 main arm 236 sub arm

Claims (4)

A shutter base plate in which an opening for exposure is formed;
A blade group that forms an opening region of the opening by an opening forming end that is a tip in a traveling direction;
A blade arm member rotatably holding the blade group, and arranged in order of the first arm and the second arm from the opening forming end side along the traveling direction of the blade group;
A driving pin connected to the first arm, and a blade driving member that rotates the first arm by driving the driving pin;
A transmission member that transmits a driving force from a motor to the blade driving member via a charge member that charges the blade driving member;
Have
When viewed from a direction parallel to the rotation axis of the arm, the blade driving member is disposed closer to the center of the opening than the charge member and farther from the transmission member. A shutter device characterized by the above.   2. The shutter device according to claim 1, wherein a normal direction at a center of a rotation locus of the driving pin and a traveling direction of the blade group are the same.   The shutter device according to claim 1, wherein the blade group performs exposure control by shielding the opening.   An image pickup apparatus comprising the shutter device according to claim 1.