JP2000056357A - Focal plane shutter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the miniaturization and speeding-up of a setting motor-driven mechanism for a focal plane shutter. SOLUTION: A setting member 19 can be reciprocated to move from an initial position to a working position so that a preceding blade driving member 2 and a following blade driving member 3 are operated to a setting position against respective driving springs 8 and 9. A setting coil 30 consisting of a shape memory alloy is attached to the setting member 19 at the one end and is attached to a base plate 1 at the other end and when a voltage is applied to the both ends, the setting member 19 is moved from the initial position to the working position. Similarly, a returning coil 40 consisting of the shape memory alloy is attached to the setting member 19 at the one end and is attached to the base plate 1 at the other end and when the voltage is applied to the both ends, the setting member 19 is moved from the working position to the initial position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focal plane shutter having an electric mechanism suitable for downsizing a camera.

[0002]

2. Description of the Related Art Recently, demands for downsizing and motorization of cameras have been further increased, and various proposals have been made and implemented in order to respond to the demands. Among them, regarding motorization, a film winding operation is automatically performed by a motor, and a lens is also driven by a motor to automatically perform focus adjustment. In addition, as for the shutter, the electrification has been advanced, and not only the set operation but also the release operation has been performed electrically. By electrifying the release operation, it is possible to release the shutter immediately after the automatic focus adjustment is performed, so that advantages such as less missed shutter chances can be obtained. Also,
By making the setting operation electric, there is an advantage that the setting operation does not have to be performed manually.

On the other hand, there is an extremely strong demand for miniaturization,
In particular, the emergence of advanced photo system films has further spurred them. However, when the shutter is electrified, the size of the camera is inevitably increased, which goes against the demand for downsizing. For example, it is common to use an electromagnet or plunger for the release operation of the focal plane shutter, but these parts are quite large as camera parts even if they are small, and they have a three-dimensional shape. Therefore, it is very difficult to mount the device compactly with other components. In the case where the shutter is set electrically, it is common to drive the motor to link the film winding. In this case, even though the motor can be shared, an interlocking mechanism such as a gear is required, which greatly restricts the layout in the camera.

[0004]

Japanese Patent Laid-Open No. Hei 10-115 discloses a technique in which the above-mentioned electromagnet, plunger or motor is used, and a shape memory alloy is used as a drive source to perform a relays operation or a set operation of a focal plane shutter.
No. 848, JP-A-10-123585, JP-A-10-123585 and the like. For example, the set operation is performed using a thin wire shape memory alloy as a drive source. This makes it possible to make the mounting structure of the camera compact to some extent.
However, the thin-line shape memory alloy generates heat when energized and generates power by self-shrinking. After this,
It returns to the initial state through a cooling process. Here, there is an inconvenience that it takes a long time since the cooling process depends on natural heat radiation as compared with the heat generation process by energization. For this reason, in the conventional electric system using a shape memory alloy, it is possible that a shutter chance may be missed.

[0005]

The following means have been taken in order to solve the above-mentioned problems of the prior art. That is, the focal plane shutter according to the present invention is assembled using a base plate having an exposure opening. The driving member for the front blade, the holding means for the front blade, the driving member for the rear blade, the holding means for the rear blade, and the set member are incorporated in the main plate. The front blade driving member is capable of reciprocating operation, and is operated from a set position by a front blade driving spring during an exposure operation,
The exposure blade is opened by the leading blade. The front blade holding means holds the front blade driving member at the set position and releases the holding force in response to a signal from the exposure time control circuit. The rear blade drive member is capable of reciprocating operation, and is operated from a set position by a rear blade drive spring during an exposure operation to cause the rear blade to close the exposure opening. The rear blade holding means holds the rear blade driving member at the set position, and releases the holding force in response to a signal from the exposure time control circuit. The set member is reciprocally movable and moves from an initial position to an operating position, and operates the leading blade drive member and the trailing blade drive member to the set position against the respective drive springs. As a feature, the present invention includes a coil for setting made of a coil-shaped shape memory alloy as a driving source. One end of the coil for this set is attached to the set member, and the other end is attached to the main plate,
When a voltage is applied to both ends, the set member is moved from the initial position to the operating position. Preferably, the focal plane shutter according to the present invention includes a return coil in addition to the setting coil. The return coil is also made of a shape memory alloy, one end of which is attached to the set member and the other end of which is attached to the main plate. Return to. Preferably, the set coil and the return coil have different wire diameters. For example, the coil for the set has a smaller wire diameter than the coil for the return. Alternatively, the set coil and the return coil have different spring constants.

After the photographing is completed, energization of the setting shape memory alloy coil is started simultaneously with winding of the film, the setting coil contracts and deforms, and the set member rotates to move from the initial position to the operating position. At the same time, the power supply to the front blade holding means and the rear blade holding means, which are composed of electromagnets, is started, and the front blade driving member and the rear blade driving member are sucked. Thereafter, prior to the release operation, the energization of the setting shape memory alloy coil is turned off, and the energization of the return shape memory alloy coil is started. As a result, the setting member is forcibly returned from the working position to the initial position. That is,
As the energization of the set coil is interrupted and the set coil is relaxed by natural cooling, the return coil is energized, so that the reset coil contracts quickly and accelerates the return of the set member to the initial position. . After that, the energization of the front blade holding unit and the rear blade holding unit composed of electromagnets is sequentially released according to a signal from the exposure time control circuit, and the front blade driving member and the rear blade driving member are sequentially operated. As a result, the front blade and the rear blade also rotate, and the exposure process is performed.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a plan view showing a state before setting immediately after photographing of a focal plane shutter according to the present invention, and FIG. 2 is a plan view showing a state after setting similarly. As shown, the focal plane shutter is assembled using a base plate 1 made of synthetic resin. As is well known, an exposure opening 1a is formed substantially at the center. In the drawing, only a part on the left side is shown. As is well known, an intermediate plate and a cover plate (not shown) are sequentially attached to the back side of the base plate 1 at a predetermined interval. An opening having a shape similar to that of the opening 1a is also formed in the intermediate plate and the cover plate, and an exposure opening as a shutter unit is formed by combining these three openings. In the case of this embodiment,
A front blade is arranged between the main plate 1 and the intermediate plate, and a rear blade is arranged between the intermediate plate and the cover plate.

On the front side of the base plate 1, shafts 1b, 1c,
1d is planted, and the shafts 1b and 1c are
Also protrudes from the back side of the device, and the portion is formed thin. Although not shown because it is well known, the front blade and the rear blade of the focal plane shutter according to the present embodiment each have a configuration in which a plurality of divided blades are pivotally supported on two arms pivotally mounted on the back side of the main plate 1. And each one arm (referred to as a main arm) has a shaft 1b and a shaft 1b.
c. The base plate 1 is formed with arc-shaped holes 1e and 1f penetrating from the front surface to the back surface.

On the front side of the base plate 1, the shaft 1b, 1c is attached to the front blade driving member 2 and the rear blade driving member 3 made of synthetic resin.
Are rotatably mounted. These driving members 2 and 3 are provided with operating pins 2a and 3a and mounting portions 2b and 3b, respectively, and rollers 2c and 3c are rotatably mounted. Of these, the operating pins 2a, 3
“a” penetrates the arc-shaped holes 1 e and 1 f and fits into holes formed in each main arm of the front blade and the rear blade. Therefore, when the leading blade driving member rotates in the counterclockwise direction, the operating pin 2a operates the main arm in the counterclockwise direction to deploy the divided blade, and when rotated in the clockwise direction, the operating pin 2a connects the main arm to the main arm. By operating clockwise, the divided blades are superimposed. On the other hand, when the rear blade driving member 3 rotates counterclockwise, the operating pin 3a operates the main arm in the counterclockwise direction to overlap the divided blades, and the operating pin 3a operates the main arm in the clockwise direction. Sometimes the split blades are deployed.

Also, a mounting portion 2 for each of the driving members 2 and 3
1 b and 3 b are formed so as to protrude toward the near side in FIG. 1, and have iron piece members 4 and 5 attached thereto, respectively. In order to clarify the specific mounting structure, the portion is shown in cross section in FIGS. The iron pieces 4 and 5 are composed of iron pieces 4a and 5a to be attracted to an electromagnet, shafts 4b and 5b loosely fitted into holes formed in the mounting portions 2b and 3b, and flanges 4c and 5c. , And is also movable in the axial direction of the shaft portions 4b and 5b. Compression springs 6 and 7 are interposed between the iron pieces 4a and 5a and the attachments 2b and 3b, respectively.
c, 5c are urged to come into contact with the mounting portions 2b, 3b, respectively. Further, the leading blade driving member 2 and the trailing blade driving member 3 are urged by the leading blade driving spring 8 and the trailing blade driving spring 9 to rotate clockwise, respectively. One end of each of the drive springs 8 and 9 is hung on the base of the above-described mounting portions 2b and 3b, and the other end is hung on the spring hooks 1q and 1r of the main plate 1.

A set member 19 made of synthetic resin is rotatably attached to the shaft 1d of the main plate 1, and is urged by a spring 20 to rotate counterclockwise. One end of the spring 20 is hung on a spring hook 19 a of the set member 19, and the other end is hung on a spring hook 1 t provided on the main plate 1. The set member 19 is formed with two cam-shaped pushing portions 19b and 19c. In addition, a terminal 19 e is implanted at one corner of the set member 19.

Although not shown because it is well known, a mounting plate (sometimes referred to as an upper ground plate) is mounted on the front side of the main plate 1 in parallel with the main plate 1. A front blade electromagnet 28 as a front blade holding means and a rear blade electromagnet 29 as a rear blade holding means are mounted on the lower surface of the mounting plate, that is, the surface on the side of the main plate 1. Therefore, these electromagnets 28 and 29 are shown by dashed lines in FIGS. The electromagnets 28 and 29 in the present embodiment have a U-shape so that the iron core members 28a and 29a can attract the iron piece members 4 and 5 with two magnetic pole portions, respectively.
The coils 28b and 29b are wound around one of the magnetic pole portions, respectively. However, since each of the two magnetic pole portions of the iron core members 28a and 29a is arranged perpendicular to the main plate 1, only one of the magnetic pole portions is visible in the drawing.

The terminal 1 implanted in one corner of the set member 19
A setting coil 30 made of a coil-shaped shape memory alloy is mounted between the terminal 9e and the terminal 1x implanted below the base plate 1. The terminal 1 provided on the set member 19
Between the terminal 9e and the terminal 1y planted on the upper part of the base plate 1, a return coil 40 also made of a coil-shaped shape memory alloy is attached. A current is selectively supplied to the pair of coils 30 and 40 from a driver 50.

Even when a certain kind of metal is subjected to a large deformation such as plastic deformation, a phenomenon in which when heated, the shape recovers as if the shape before deformation is stored is called a shape memory effect. The metal possessed is called a shape memory alloy. The shape memory effect is a phenomenon associated with solid-state transformation of a metal called thermoelastic martensite. In this solid state transformation, it is possible to exchange heat energy and elastic energy within a limited range. Shape memory alloys can be considered as solid state Stirling engine-like actuators because of their behavior similar to a gas-enclosed cylinder. As the actuator that can be actually used, a Ti—Ni-based alloy is frequently used because it can be used as a polycrystal, the amount of recovery strain, fatigue characteristics, operating temperature range, safety, durability, and the like. Ti-Ni-based shape memory alloys have a relatively large electric resistance as a metal and can be easily heated by energization. This indicates that it is possible to make an actuator that can extract motion only by passing a current through the shape memory alloy. In particular, a coil-shaped shape memory alloy can obtain a relatively large displacement amount and a large kinetic force when energized, and is suitable as an actuator. In addition, since the coiled shape memory alloy can be provided with a spring property, as shown in FIGS. 1 and 2,
Suitable for driving the set member of the focal plane shutter. In the present embodiment, the setting coil 30 and the return coil 40 act in opposite directions to each other, and the urging force of the spring 20 is also applied to the set member 19. In order to balance these mechanical forces, the setting coil 30 and the returning coil 40 have different and appropriate spring constants. Alternatively, the setting coil 30 and the returning coil 40 may have different wire diameters from each other. In the present embodiment, the coil 30 for setting has a smaller wire diameter than the coil 40 for returning. However, the present invention is not limited to this.
The spring property of 0 is appropriately set in accordance with the design specifications of the focal plane shutter, and the spring 20 can be omitted.

The operation of the focal plane shutter according to the present invention will be described in detail with reference to FIGS. FIG. 1 shows a state immediately after the end of shooting. Therefore, the driving member 2 for the front blade and the driving member 3 for the rear blade are in a state where the exposure operation has been completed by the respective drive springs 8 and 9, and the photographer still holds down the relays button of the camera. is there. In this state, the divided blades of the leading blade (not shown) are stored in a superimposed position below the exposure opening 1a, and the divided blades of the rear blade are unfolded to cover the exposure opening 1a. I have. The set member 19 has returned to the initial position. Note that the initial position of the set member 19 may be regulated by a stopper. However, in the present embodiment, the initial position of the set member 19 is regulated by the balance between the pair of shape memory alloy coils 30 and 40.

In this state, when the pressing force of the release button is released, the power switch is turned off. However, even when the power switch is turned off, the film winding motor and the setting shape memory alloy coil 30 are kept for a predetermined time.
Can be supplied with power. The film is wound by the OFF signal of the power switch, and at the same time, a voltage is applied to the shape memory alloy coil 30. Therefore, the shape memory alloy coil 30 for setting shrinks rapidly and shortens, and rotates the setting member 19 clockwise against the spring 20. By this rotation, the set member 19 is
First, the pressing portion 19b presses the roller 2c which is a non-pressing portion. Therefore, the leading blade driving member 2 rotates counterclockwise against the leading blade driving spring 8, and the main arm of the leading blade (not shown) is rotated counterclockwise about the shaft 1b by the operating pin 2a. Let it. As a result, the split blades (not shown) start operating upward while being deployed. When a part of the slit forming blade overlaps the slit forming blade of the rear blade by a predetermined amount, the other pushing portion 19c of the set member 19 starts pressing the roller 3c of the rear blade driving member 3.

In this manner, the roller 3c is moved
When the rear blade drive member 3 is pressed counterclockwise against the drive spring 9, the operating pin 3a causes the main arm of the rear blade (not shown) to rotate counterclockwise with the shaft 1c. Rotate. As a result, the split blades of the rear blade operate upward while overlapping. Immediately thereafter, the iron piece portions 4a and 5a of the iron piece members 4 and 5 successively come into contact with the iron core members 28a and 29a. After that, the contraction of the shape memory alloy coil 30 ends,
The setting member 19 stops at the operation position. FIG. 2 shows the state at that time.

At this time, the iron piece portions 4a, 5 of the iron piece members 4, 5
a is in close contact with the iron core members 28a and 29a, and the compression springs 6 and 7 are compressed.
c, 5c and the attachment parts 2b, 3b are in a non-contact state. The front blade is in a developed state and covers the exposure opening 1a, and the rear blade is in a superimposed state and stored at a position above the exposure opening 1a. After the shutter has been set in this manner and the film winding operation is subsequently completed, the camera is ready for the next photographing.

Next, the release operation will be described. When the relays button of the camera is pressed, the power switch is closed in the initial stage, the photometric circuit and the distance measuring circuit operate, and both coils 28b and 28b of the electromagnet 28 for the leading blade and the electromagnet 29 for the trailing blade.
Electric current is supplied to 29b, and the iron core members 28a and 29a are excited. Therefore, the iron piece portions 4a, 5a of the iron piece members 4, 5
Is magnetically attracted to the iron core members 28a and 29a. At this stage, the photographer can confirm the suitability of the photographing conditions and the like using a known display. After that, when the release button is further pressed, the lens is extended based on the result of the distance measurement, and almost simultaneously with the stop, the energization to the set shape memory alloy coil 30 that has finished its role is turned off. As a result, the coil 30 starts cooling and transforms from a contracted state to an expanded state. However, the transformation is relatively slow because it is based on natural cooling. Therefore, although the spring 20 is assisted in this state, it takes time for the set member 19 to return to the initial position, and the shutter chance is reduced. Therefore, in the present invention, the energization of the setting coil 30 is cut off, and the energization of the return coil 40 is performed by the driver 50. As a result, the return coil 40 starts contracting promptly, and the set member 19 rotates counterclockwise and immediately returns to the initial position. As described above, in the present invention, the reciprocating movement of the set member 19 between the initial position and the operating position is accelerated by using a pair of the shape memory alloy coils 30 and 40 acting in opposite directions. As described above, the set member 19 returns to the initial position by the contraction force of the return coil 40 in addition to the assisting force of the spring 20. The exposure time control circuit is triggered in conjunction with the returning operation of the setting member 19.

When the exposure time control circuit is triggered and a predetermined delay time has elapsed, the coil 28 of the electromagnet 28
The power supply to b is cut off. As a result, the leading blade drive member 2 rotates clockwise by the force of the leading blade drive spring 8, and operates the main arm of the leading blade clockwise by the operating pin 2a. For this reason, the plurality of divided blades constituting the leading blade are superimposed and open the exposure opening 1a. Immediately after the opening is completed, the operating pin 2a collides with the lower end edge of the hole 1e, the bouncing is stopped by means (not shown), and the operating pin 2a is stored at a position below the exposure opening 1a and stopped.

After a predetermined time corresponding to the photometry result after the energization of the coil 28a of the electromagnet 28 for the front blade is cut off, the energization of the coil 29b of the electromagnet 29 for the rear blade is cut off. Therefore, the biasing force of the rear blade drive spring 9 rotates the rear blade drive member 3 clockwise, and the operating pin 3a operates the main arm of the rear blade clockwise.
As a result, the plurality of divided blades constituting the rear blade group are developed and close the exposure opening 1a. And
Immediately after the closing, the operating pin 3a collides with the lower end edge of the hole 1f, the bouncing is stopped by means (not shown), and the operating pin 3a stops while covering the exposure opening 1a. The state at this time is as shown in FIG.

[0022]

As described above, according to the present invention, since a shape memory alloy coil is used as a drive source to set a focal plane shutter, a conventional three-dimensionally shaped electromagnet or plunger is used. Compared to using
The space in the camera can be used freely, making it ideal for downsizing the camera. In particular, since a pair of shape memory alloy coils acting in opposite directions are used, the shutter can be set and reset quickly.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a focal plane shutter according to the present invention, and shows a state before setting immediately after photographing is completed.

FIG. 2 is a plan view showing a state after setting.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 ground plate 1 a exposure opening 2 front blade drive member 3 rear blade drive member 19 set member 28 electromagnet 29 electromagnet 30 set shape memory alloy coil 40 return shape memory alloy coil 50 driver

Claims (5)

[Claims] 1. A base plate having an exposure opening, and a front blade drive that is reciprocally operable and is operated from a set position by a front blade driving spring during the exposure operation to open the exposure opening to the front blade. A holding member for holding the front blade driving member at the set position and releasing the holding force in response to a signal from the exposure time control circuit; and a reciprocating operation possible for the rear blade during the exposure operation. A driving member for a rear blade which is actuated from a set position by a driving spring to cause the rear blade to close the opening for exposure; and a holding force for holding the driving member for the rear blade at the set position and for responding to a signal from an exposure time control circuit. Holding means for releasing the rear blade, and reciprocally movable from the initial position to the operating position to move the driving member for the front blade and the driving member for the rear blade to the set position against each driving spring. Activate The set member is made of a coil-shaped shape memory alloy, one end of which is attached to the set member and the other end of which is attached to the base plate. When a voltage is applied to both ends, the set member is moved from the initial position to the operating position. A focal-plane shutter, comprising: 2. A coil made of a shape memory alloy, one end of which is attached to the set member and the other end of which is attached to the base plate, and when a voltage is applied to both ends, the set member is moved from an operation position to an initial position. 2. The focal plane shutter according to claim 1, further comprising a return coil for moving the focal plane shutter. 3. The focal plane shutter according to claim 2, wherein the setting coil and the return coil have different wire diameters from each other. 4. The focal plane shutter according to claim 3, wherein the setting coil has a smaller wire diameter than the return coil. 5. The focal plane shutter according to claim 2, wherein the setting coil and the return coil have different spring constants.