JP7660456B2 - Focal Plane Shutter - Google Patents

Description

The present invention relates to a focal plane shutter, and in particular to a focal plane shutter for an imaging device having at least one blade.

In imaging devices such as cameras, the exposure aperture is opened and closed by moving the shutter blades at high speed to expose the imaging element. Conventionally, focal plane shutters, which move the shutter blades in one direction at high speed using an actuator, have been known as blade drive devices that drive the shutter blades. In such focal plane shutters, a buffer member is placed at the end of the movement path of the drive unit that drives the shutter blades to prevent the shutter blades from bouncing too much or being damaged by the impact caused when the shutter blades are driven at high speed (see, for example, Patent Document 1).

However, even when such a buffer member is provided, it is difficult to sufficiently prevent the shock generated when the shutter blades are driven at high speed from being transmitted from the base plate of the focal plane shutter to the camera housing via the actuator drive shaft. If a shock is applied to the camera body, it will adversely affect the captured image. Therefore, in order to reduce the transmission of such a shock to the camera housing, it is possible to provide a shock absorbing mechanism between the focal plane shutter and the camera housing, but this would increase the overall size of the camera.

JP 2015-64559 A

The present invention was made in consideration of these problems with the conventional technology, and aims to provide a focal plane shutter that is compact in structure and prevents the shock caused by the blades being driven from being transmitted to the outside.

According to one aspect of the present invention, there is provided a focal plane shutter that is capable of realizing a compact structure and that is less susceptible to external transmission of shocks caused by the driving of the blades. This focal plane shutter comprises a base plate having an opening, at least one blade that is movable to open and close the opening of the base plate, an arm portion connected to the at least one blade, and a drive unit that drives the at least one blade. The drive unit includes a base portion, a drive shaft attached to the base portion, and a drive lever having an arm connecting portion connected to the arm portion and capable of rotating around the drive shaft. The focal plane shutter further comprises a shock absorbing member disposed between the base plate and the base portion of the drive unit.

FIG. 1 is a front view showing a focal plane shutter according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of the focal plane shutter shown in FIG. FIG. 3 is an enlarged perspective view showing some components of the focal plane shutter shown in FIG.

The following describes in detail an embodiment of a focal plane shutter according to the present invention with reference to Figs. 1 to 3. In Figs. 1 to 3, identical or corresponding components are given the same reference numerals and duplicated descriptions are omitted. In Figs. 1 to 3, the scale and dimensions of each component may be exaggerated or some components may be omitted. In the following description, unless otherwise specified, terms such as "first" and "second" are used only to distinguish components from each other and do not indicate a specific order or sequence.

1 is a front view showing a focal plane shutter 1 according to an embodiment of the present invention. As shown in FIG. 1, the focal plane shutter 1 according to this embodiment includes a base plate 10 in which a rectangular opening S is formed, six blades 31, 32 housed in a space (blade chamber) formed between the base plate 10 and a cover plate (not shown), and a drive unit 20 for driving (moving) these blades 31, 32. An opening of approximately the same shape as the opening S of the base plate 10 is formed in the cover plate, and an exposure opening is formed by the opening S of the base plate 10 and the opening of the cover plate. This focal plane shutter 1 is incorporated in a camera equipped with an image sensor (not shown) such as a CCD or CMOS sensor, and is fixed to the camera body (not shown) by, for example, inserting a screw into the fixing hole 2. The image sensor is located on the front side of the focal plane shutter 1 in FIG. 1, and light from a subject passes through the above-mentioned exposure opening and enters the image sensor on the front side of the paper.

Each of the blades 31 and 32 is a thin plate-like member that extends in the X direction as a whole. In this embodiment, three blades 31 are stacked in the Z direction to form the rear curtain (rear blades) of the focal plane shutter 1. Also, three blades 32 are stacked in the Z direction to form the front curtain (front blades) of the focal plane shutter 1.

The focal plane shutter 1 also includes rear blade arms 41, 42 (arm portions) connected to the rear blade 31. Each rear blade 31 is connected to the rear blade arms 41, 42 by a connecting portion 51 so as to be rotatable with respect to each other. The rear blade arm 41 is configured to be rotatable around a support shaft 61, and the rear blade arm 42 is configured to be rotatable around a support shaft 62. With this configuration, each rear blade 31 and the rear blade arms 41, 42 form a link mechanism.

Similarly, the focal plane shutter 1 includes leading blade arms 43, 44 (arm portions) that are connected to the leading blade 32. Each leading blade 32 is connected to the leading blade arms 43, 44 by a connecting portion 52 so that they can rotate with each other. The leading blade arm 43 is configured to be rotatable around a support shaft 63, and the leading blade arm 44 is configured to be rotatable around a support shaft 64. With this configuration, each leading blade 32 and the leading blade arms 43, 44 form a link mechanism.

2 is an exploded perspective view of the focal plane shutter 1. As shown in FIG. 2, the drive unit 20 of the focal plane shutter 1 includes a plate-shaped base 21, drive shafts 22, 23 and a rotating shaft 24 extending from the base 21 in the +Z direction, a trailing blade drive lever 71 rotatably attached to the drive shaft 22, a leading blade drive lever 72 rotatably attached to the drive shaft 23, a control lever 73 rotatably attached to the rotating shaft 24 and capable of controlling the rotation of the trailing blade drive lever 71 and the leading blade drive lever 72, a cover plate 74 covering the trailing blade drive lever 71, the leading blade drive lever 72 and the control lever 73, and a fixed shaft 75 attached to the cover plate 74. The drive shaft 22 is provided coaxially with the support shaft 61 (see FIG. 1), and the drive shaft 23 is provided coaxially with the support shaft 63 (see FIG. 1).

Between the base 21 of the drive unit 20 and the base plate 10, a shock absorbing member 80 made of a flexible material such as butyl rubber or elastomer is disposed. A recess 12 having a shape corresponding to the shape of the shock absorbing member 80 is formed in the base plate 10, and the shock absorbing member 80 is accommodated in the recess 12 of the base plate 10. For example, the thickness of most of the shock absorbing member 80 in the Z direction is about 0.5 mm, and the depth of the recess 12 of the base plate 10 in the Z direction is about 0.5 mm.

2, the fixed shaft 75 attached to the cover plate 74 is inserted into the shaft hole 27 formed in the base 21 and protrudes from the base 21 in the -Z direction. The shock absorbing member 80 has recesses 86 and 87 for passing the fixed shaft 75 extending from the base 21 in the -Z direction. As shown in FIG. 3, the fixed shaft 75 extending from the base 21 in the -Z direction is fixed to the base plate 10 by the recesses 86 and 87 of the shock absorbing member 80 without coming into contact with the shock absorbing member 80. For example, a screw (not shown) is inserted into the circular hole 17 of the base plate 10 from the -Z direction side, and the drive unit 20 is fixed to the base plate 10 by screwing the screw into the end of the fixed shaft 75 on the -Z direction side. In this way, the fixed shaft 75 can be fixed to the base plate 10 without coming into contact with the flexible shock absorbing member 80, so that the drive unit 20 can be firmly fixed to the base plate 10.

The rear blade drive lever 71 has a shaft portion 71A through which the drive shaft 22 is inserted, an attraction portion 71B that is attracted to an electromagnet (not shown), and an arm connection portion 71C that is inserted into a lever hole 41A (see FIG. 1) formed in the rear blade arm 41 and connected to the rear blade arm 41. The base portion 21 has an arc hole 25 along an arc centered on the drive shaft 22, and the base plate 10 also has an arc hole 13 along an arc centered on the drive shaft 22. The shock absorbing member 80 also has an arc hole 81 along an arc centered on the drive shaft 22. The arm connection portion 71C of the rear blade drive lever 71 is connected to the lever hole 41A of the rear blade arm 41 through these arc holes 25, 81, and 13.

The leading blade drive lever 72 has a shaft portion 72A through which the drive shaft 23 is inserted, an attraction portion 72B that is attracted to an electromagnet (not shown), and an arm connection portion 72C that is inserted into a lever hole 43A (see FIG. 1) formed in the leading blade arm 43 and connected to the leading blade arm 43. A notch 26 is formed in the base 21 along an arc centered on the drive shaft 23, and an arc hole 14 is formed in the base plate 10 along an arc centered on the drive shaft 23. In addition, a notch 82 is formed in the shock absorbing member 80 along an arc centered on the drive shaft 23. The arm connection portion 72C of the leading blade drive lever 72 is connected to the lever hole 43A of the leading blade arm 43 through these notches 26, 82 and the arc hole 14.

In this configuration, when the trailing blade drive lever 71 is rotated around the drive shaft 22, the trailing blade arm 41 connected to the arm connection part 71C of the trailing blade drive lever 71 rotates around the support shaft 61. When the trailing blade arm 41 rotates around the support shaft 61, the above-mentioned link mechanism causes the trailing blade arm 42 to also rotate around the support shaft 62, and the trailing blades 31 move mainly in the ±Y direction on the XY plane while changing the area where they overlap.

The trailing blade drive lever 71 is rotated to the charge position in the +Y direction by the control lever 73, and the suction part 71B is attracted to the electromagnet at the charge position, so that the trailing blade drive lever 71 is held in the charge position. When the control lever 73 then returns to the initial position and the electromagnet is de-energized, the trailing blade drive lever 71 rotates toward the blade travel completion position by the force of a drive spring (not shown), and the trailing blade 31 moves mainly in the -Y direction.

Similarly, when the leading blade drive lever 72 is rotated around the drive shaft 23, the leading blade arm 43 connected to the arm connection part 72C of the leading blade drive lever 72 rotates around the support shaft 63. When the leading blade arm 43 rotates around the support shaft 63, the leading blade arm 44 also rotates around the support shaft 64 due to the link mechanism described above, and the leading blades 32 move mainly in the ±Y direction on the XY plane while changing the area where they overlap.

The leading blade drive lever 72 is rotated to the charge position in the +Y direction by the control lever 73, and the suction portion 72B is attracted to the electromagnet at the charge position, so that the leading blade drive lever 72 is held in the charge position. When the control lever 73 then returns to the initial position and the electromagnet is de-energized, the leading blade drive lever 72 rotates toward the blade travel completion position by the force of a drive spring (not shown), and the leading blade 32 moves mainly in the -Y direction.

It is known that when the drive levers 71 and 72 rotate from the charge position to the blade travel completion position, a particularly strong impact is applied to the drive shafts 22 and 23. This impact is transmitted to the base 21 on which the drive shafts 22 and 23 are mounted. In this embodiment, however, since the impact absorbing member 80 is disposed between the base 21 and the base plate 10, the impact transmitted to the base 21 is absorbed by the impact absorbing member 80 and is not easily transmitted to the base plate 10. Therefore, the impact caused by the drive of the drive levers 71 and 72 is not easily transmitted from the base plate 10 to the outside (camera body), and the adverse effect on the captured image is reduced. In addition, since the impact caused by the drive of the drive levers 71 and 72 can be mitigated inside the focal plane shutter 1, there is no need to provide a mechanism for mitigating the impact outside the focal plane shutter 1, and the structure of the entire camera can be made compact.

In addition, if a shock-absorbing mechanism is provided outside the focal plane shutter 1, a misalignment may occur between the base plate of the focal plane shutter that receives the shock and the image sensor of the camera where the shock is absorbed, which may adversely affect the captured image. However, in this embodiment, the shock transmitted to the base plate 10 of the focal plane shutter 1 is absorbed, thereby preventing misalignment between the base plate 10 of the focal plane shutter 1 and the image sensor of the camera.

As shown in FIG. 2, the end of the arc hole 81 formed in the shock absorbing member 80 is made thick, and an arc-shaped damper portion 83 is formed at the end of the arc hole 81. The arm connection portion 71C of the trailing blade drive lever 71 rotating toward the blade travel completion position hits this damper portion 83, so that the shock when the trailing blade drive lever 71 stops is absorbed and mitigated by the damper portion 83, and the shock transmitted to the base plate 10 can be further reduced. In addition, damper accommodating portions 13A and 25A that accommodate the damper portion 83 of the shock absorbing member 80 are formed at the end of the arc hole 13 formed in the base plate 10 on the -Y direction side and the end of the arc hole 25 formed in the base 21 on the -Y direction side, respectively.

Similarly, the end of the notch 82 formed in the shock absorbing member 80 is made thick, and an arc-shaped damper portion 84 is formed at the end of the notch 82. When the arm connection portion 72C of the leading blade drive lever 72 rotating toward the blade travel completion position hits this damper portion 84, the shock when the leading blade drive lever 72 stops is absorbed and mitigated by the damper portion 84, so that the shock transmitted to the base plate 10 can be further reduced. In addition, damper accommodating portions 14A and 26A that accommodate the damper portion 84 of the shock absorbing member 80 are formed at the end of the arc hole 14 formed in the base plate 10 on the -Y direction side and the end of the notch 26 formed in the base 21 on the -Y direction side, respectively.

In addition, because these damper sections 83, 84 are configured as part of the shock absorbing member 80, the shock caused by the actuation of the drive levers 71, 72 is absorbed not only by the damper sections 83, 84 but also by other parts of the shock absorbing member 80, so that the shock caused by the actuation of the drive levers 71, 72 can be more effectively mitigated.

The base plate 10 in this embodiment also has two positioning protrusions 15 that protrude toward the base 21 of the drive unit 20. Correspondingly, the shock absorbing member 80 is formed with a positioning hole 85 that accommodates the positioning protrusions 15 of the base plate 10. With this configuration, the shock absorbing member 80 can be accurately positioned relative to the base plate 10 simply by aligning the positioning protrusions 15 formed on the base plate 10 with the positioning holes 85 of the shock absorbing member 80 and inserting the positioning protrusions 15 of the base plate 10 into the positioning holes 85 of the shock absorbing member 80.

As described above, the shock absorbing member 80 in this embodiment is housed in the recess 12 formed in the base plate 10, so the shock absorbing member 80 can be disposed between the base 21 of the drive unit 20 and the base plate 10 without excessively increasing the thickness of the focal plane shutter 1 in the Z direction.

The material, shape, size, thickness, and degree of compression between the base 21 of the drive unit 20 and the base plate 10 of the shock absorbing member 80 can be changed as appropriate to suit parameters such as the size of the exposure opening of the focal plane shutter 1 and the speed of the blades 31 and 32.

As described above, one aspect of the present invention provides a focal plane shutter that is compact in structure and does not easily transmit shocks caused by the driving of the blades. The focal plane shutter includes a base plate having an opening, at least one blade that can move to open and close the opening in the base plate, an arm portion connected to the at least one blade, and a drive unit that drives the at least one blade. The drive unit includes a base portion, a drive shaft attached to the base portion, and a drive lever that has an arm connecting portion connected to the arm portion and is rotatable around the drive shaft. The focal plane shutter further includes a shock absorbing member disposed between the base plate and the base portion of the drive unit.

With this configuration, the strong impact generated when the drive lever is driven is transmitted to the base of the drive unit, but because a shock absorbing member is disposed between the base plate and the base, the impact transmitted to the base is absorbed by the shock absorbing member and is less likely to be transmitted to the base plate. This results in a structure in which the impact caused by driving the drive lever is less likely to be transmitted from the base plate to the outside (such as the camera body). In this way, the impact caused by driving the drive lever can be mitigated inside the focal plane shutter, eliminating the need to provide an impact mitigation mechanism outside the focal plane shutter and allowing for a compact structure to be realized.

The shock absorbing member preferably has a damper portion that comes into contact with the drive lever of the drive unit to reduce the shock when the drive lever stops. When the drive lever comes into contact with such a damper portion, the shock when the drive lever stops is absorbed and reduced by the damper portion, so that the shock transmitted to the base plate can be further reduced. In particular, since the damper portion is configured as a part of the shock absorbing member, the shock caused by the drive of the drive lever is absorbed not only by the damper portion but also by other parts of the shock absorbing member, so that the shock caused by the drive of the drive lever can be more effectively reduced.

The drive unit may further include at least one fixed shaft attached to the base. In this case, it is preferable that the shock absorbing member has a recess formed therein for passing the at least one fixed shaft therethrough and fixing the fixed shaft to the base plate. The recess of the shock absorbing member allows the fixed shaft attached to the base plate to be fixed to the base plate without coming into contact with the shock absorbing member, thereby making it possible to firmly fix the drive unit to the base plate.

The base plate may have at least one positioning protrusion that protrudes toward the base of the drive unit. The shock absorbing member may also have a positioning hole formed therein that accommodates the at least one positioning protrusion of the base plate. With this configuration, the shock absorbing member can be accurately positioned relative to the base plate simply by aligning the protrusion formed on the base plate with the positioning hole of the shock absorbing member and inserting the protrusion of the base plate into the positioning hole of the shock absorbing member.

The base plate may have a recess formed therein, and the shock absorbing member may be housed within the recess of the base plate. By housing the shock absorbing member in a recess formed in the base plate in this manner, the shock absorbing member can be disposed between the base of the drive unit and the base plate without excessively increasing the thickness of the focal plane shutter.

Though we have described preferred embodiments of the present invention, it goes without saying that the present invention is not limited to the above-mentioned embodiments and may be embodied in various different forms within the scope of its technical concept.

REFERENCE SIGNS LIST 1 focal plane shutter 10 base plate 12 recess 13, 14 arc hole 15 positioning protrusion 20 drive unit 21 base 22, 23 drive shaft 24 rotation shaft 25 arc hole 26 notch 27 shaft hole 31 rear blade 32 leading blade 41, 42 rear blade arm (arm portion)
43, 44 Leading blade arm (arm part)
51, 52 Connection portion 61 to 64 Support shaft 71 Trailing blade drive lever 71A Shaft portion 71B Suction portion 71C Arm connection portion 72 Leading blade drive lever 72A Shaft portion 72B Suction portion 72C Arm connection portion 73 Control lever 74 Cover plate 75 Fixed shaft 80 Impact absorbing member 81 Circular hole 82 Notch 83, 84 Damper portion 85 Positioning hole 86, 87 Relief portion S Opening

Claims (5)

A base plate having an opening formed therein;
At least one blade movable to open and close the opening in the base plate;
An arm portion connected to the at least one blade;
A drive unit for driving the at least one blade,
A base and
A drive shaft attached to the base;
a drive unit including a drive lever having an arm connecting portion connected to the arm portion and rotatable about the drive shaft;
a shock absorbing member disposed between the base plate and the base of the drive unit. The focal plane shutter according to claim 1, wherein the shock absorbing member has a damper portion that mitigates the shock that occurs when the drive lever of the drive unit comes into contact with the drive lever and stops. The drive unit further includes at least one fixed shaft attached to the base;
The impact absorbing member is provided with a recess for allowing the at least one fixed shaft to pass therethrough and for fixing the impact absorbing member to the base plate.
3. The focal plane shutter according to claim 1 or 2. the base plate has at least one positioning protrusion protruding toward the base of the drive unit;
The shock absorbing member is formed with a positioning hole for receiving the at least one positioning protrusion of the main plate.
4. The focal plane shutter according to claim 1. A recess is formed in the base plate,
The shock absorbing member is accommodated in the recess of the main plate.
The focal plane shutter according to any one of claims 1 to 4.

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