JP4298395B2 - Camera shutter device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a camera shutter device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, electromagnetic actuators such as stepping motors and solenoids have been used as drive sources for camera shutter opening and closing operations.
A mechanism using a fibrous shape memory alloy as a drive source has also been proposed. (For example, see Patent Document 1 and Patent Document 2)
As shown in Patent Document 1, the contraction operation of the fibrous shape memory alloy by energization was used for the movement of the shutter blade driving member to the release start position and the release of the shutter blade locking auxiliary member at the initial stage of the release. Things have been proposed.
Further, as shown in Patent Document 2, there has been proposed one in which a fibrous shape memory alloy is connected to a drive lever of a shutter blade and the shutter is opened by a contraction operation thereof.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-123583 [Patent Document 2]
Japanese Utility Model Publication No. 8-9713 [0004]
[Problems to be solved by the invention]
Since the conventional electromagnetic actuator basically uses a magnetic force generated by a current magnetic field as a driving source, there has been a limit to downsizing the mechanism while increasing the driving force.
Further, the mechanism using the fibrous shape memory alloy as the drive source cannot prevent inadvertent operation from being caused when the ambient temperature becomes higher than the transformation temperature of the shape memory alloy.
In addition, since it takes time to heat the fibrous shape memory alloy from the ambient temperature to the shrinkage start temperature, there is a drawback that the release time lag becomes long.
[0005]
An object of the present invention is to prevent the camera shutter device using a fibrous shape memory alloy as a drive source from being affected by the environmental temperature.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the invention described in claim 1 is directed to a shutter blade driving lever, a closing spring that normally urges the shutter blade in the closing direction, and a contraction operation by energization to close the shutter blade. A camera shutter device connected to one end of a fibrous shape memory alloy that opens against a biasing force,
A latch mechanism is provided that holds the other end of the fibrous shape memory alloy in a fixed state during a release operation and releases the hold in the fixed state except during a release operation.
[0007]
According to the first aspect of the present invention, since the other end portion of the fibrous shape memory alloy is fixed during the release operation, the shutter blades are opened by heat generation contraction of the fibrous shape memory alloy by energization. Can do.
In addition, since the other end of the fibrous shape memory alloy is fixed and released except during the release operation, even if the fibrous shape memory alloy contracts due to an increase in the environmental temperature, inadvertent shutter operation is prevented. I can do it.
[0008]
According to a second aspect of the present invention, in the camera shutter device according to the first aspect, the other end of the fibrous shape memory alloy having one end connected to the drive lever is connected, and is fixed by the latch mechanism. A pivot lever held by
And an auxiliary spring that is connected to the rotating lever and biases the rotating lever in a direction held by a latch mechanism with a weaker force than the closing spring.
[0009]
According to the second aspect of the present invention, the force of the auxiliary spring that biases the rotating lever in the direction held by the latch mechanism is set to be weaker than the force of the closing spring that biases the drive lever in the closing direction. Therefore, the rotating lever can be rotated against unintentional contraction of the fibrous shape memory alloy other than the release operation, and an inadvertent shutter operation can be prevented.
[0010]
According to a third aspect of the present invention, in the camera shutter device according to the first or second aspect, the latch mechanism is a holding magnet that attracts the rotating lever or a holding lever that is engaged with the rotating lever. It is either of these.
[0011]
According to a fourth aspect of the present invention, in the camera shutter device according to any one of the first to third aspects of the present invention, the camera shutter device further comprises a control means for energizing and preheating the fibrous shape memory alloy in the first stage of the release operation. Features.
[0012]
According to the invention described in claim 4, by preheating the fibrous shape memory alloy in the first stage of the release operation, the fibrous shape memory alloy is heated to the shrinkage start temperature in the second stage of the release operation. The time can be shortened, and the time lag between the release operation and the shutter operation can be shortened.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0014]
[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of a shutter device according to an embodiment to which the present invention is applied. As shown in FIG. 1, the shutter device 1 includes a shutter portion 2 and a latch mechanism 3.
[0015]
In the shutter unit 2, the shutter blade 4 covering the shutter opening 5 rotates between the shutter open position and the closed position about the rotation shaft 6.
When the shutter blade 4 is in the closed position, the blade drive lever 12 abuts against the rotation stop 10 and is further biased by the closing spring 9 so as to maintain the closed position.
One end of a fibrous shape memory alloy (SMA) 8 is fixed to the pin-shaped electrode A7 provided on the blade drive lever 12. The shutter blade 4 is rotated to the open position by the heat shrinkage operation caused by energization of the fibrous shape memory alloy 8. The fibrous shape memory alloy 8 functions as an actuator that transitions between tension contraction and relaxation extension in the length direction.
[0016]
In FIG. 5, the fibrous shape memory alloy 8 generates heat when energized, and generates a driving force by abrupt tension contraction when the temperature exceeds the shrinkage start temperature. Further, when the current is cut off, the heat becomes less than the relaxation / elongation start temperature due to heat dissipation and returns to the original length.
The fibrous shape memory alloy 8 contracts in tension when it generates heat, but the heat source performs tension contraction when the ambient temperature becomes equal to or higher than the contraction start temperature without being energized.
[0017]
In FIG. 1, the other end of the fibrous shape memory alloy 8 is fixed to a pin-shaped electrode B 15 provided on a rotating lever 13 that forms the latch mechanism 3.
The rotating lever 13 is a free end that can rotate around a rotating shaft 17, and is further urged by an auxiliary spring 16 in a direction in contact with the holding magnet 14. At this time, the biasing force of the auxiliary spring 16 is set sufficiently weaker than the biasing force of the closing spring 9.
The movement amount L of the electrode A7 required for the rotation operation of the shutter blade 4 from the closed position to the fully open position is equal to the amount of contraction strain due to the energization heat generation of the fibrous shape memory alloy 8.
Further, the shiftable movement amount Lm when the holding magnet 14 of the electrode B15 of the rotating lever 13 is off is set to satisfy the relationship L <Lm.
[0018]
FIG. 6 shows a circuit diagram as an embodiment.
Connected in series with the power source E is a switch S1 that is turned on in the first release operation. The switch S2 is also a switch that is turned on in the second stage of the release operation.
Cds is a light receiving element whose resistance value changes with subject luminance.
The charging voltage of the capacitor C1 connected in series with the light receiving element Cds is connected to the non-inverting input terminal of the comparator COMP, and the inverting input terminal of the comparator COMP is connected to the reference potential obtained by dividing the power supply voltage by the resistors R1 and R2. Has been.
The transistor Q1 shorts both ends of the capacitor C1 when the switch S1 is on, but when the switch S2 is on, the transistor Q1 is turned off and charging of the capacitor C1 is started.
The electrodes A7 and B15 of the fibrous shape memory alloy SMA8 are connected to the output of the comparator COMP via the holding magnet Mg14 and the transistor Q2.
The base of the transistor Q2 is connected to the collector of the transistor Q3 via the resistor R3, and the base of the transistor Q3 is connected to the power source E via the resistor R4 and the switch S1.
Similarly, the base of the transistor Q3 is also connected to the collector of the transistor Q4.
The base of the transistor Q4 is connected to the power supply through the resistor R5, the switch P11, and the switch S1, and is connected to the switch S2 through the diode D1. The base of the transistor Q1 is also connected here.
Further, this connection point is connected to a power source via a resistor R6 and a switch S1.
Here, as shown in FIGS. 1 and 2, the switch P <b> 11 is provided so as to detect the initial shift amount at the end of the drive lever 12 of the shutter blade 4. That is, when the drive lever 12 is slightly changed, the drive lever 12 is turned on. However, this shift amount does not lead to the start of shutter opening.
[0019]
The operation of the shutter device 1 configured as described above will be described.
When the switch S1 in FIG. 6 is turned on in the first stage of the release operation of the camera (not shown), the transistor Q1 is turned on. Therefore, the output of the comparator COMP is LOW, the holding magnet Mg14 is turned on, and the rotating lever 13 in FIG. Adsorb and latch.
Thereby, when the fibrous shape memory alloy SMA8 contracts due to energization heat generation, the shutter blade 4 can be rotated in the opening direction.
At this time, in the initial state shown in FIG. 1, since the switch P11 is turned off, the transistor Q4 in FIG. 6 is turned off and the transistors Q2 and Q3 are turned on.
As a result, the fibrous shape memory alloy SMA8 is energized between the electrodes A7 and B15, and begins to contract by tension due to heat generation.
[0020]
As shown in FIG. 2, the switch P11 is turned on when the shutter blade 4 undergoes a slight transition that does not reach the opening. Accordingly, when the transistor Q4 in FIG. 6 is turned on and the transistors Q2 and Q3 are turned off, the energization of the fibrous shape memory alloy SMA8 is cut off, and the shutter blade 4 does not change any more.
As an example, if switching on and off of the switch P11 is performed with a transition amount of 1% of the contraction strain amount, the switch P11 is turned on at 70 ° C. from FIG. 5 to prevent further transition.
Then, the fibrous shape memory alloy SMA8 expands by heat dissipation, and the switch P11 is turned off again at 60 ° C. or lower.
Thereafter, this heat generation and heat release are repeated, and the temperature of the fibrous shape memory alloy SMA8 is preheated in the range of about 60 ° C. to 70 ° C.
By this preheating operation, it is possible to shorten the time for heating from the environmental temperature of the camera to the contraction start temperature at the start of exposure of the second stage of the subsequent release operation, and to shorten the release time lag.
[0021]
When the switch S2 in FIG. 6 is turned on in the second stage of the release operation, the transistor Q1 is turned off, and the capacitor C1 starts charging with a current determined by the resistance value of the light receiving element Cds (resistance value proportional to the subject brightness).
On the other hand, when the switch S2 is turned on, the base of the transistor Q4 is connected to the GND by the diode D1, so that the transistor Q4 is turned off regardless of the state of the switch P11, and the transistors Q2 and Q3 are turned on.
Therefore, when the fibrous shape memory alloy SMA8 is energized through the electrodes A7 and B15 and generates heat up to 80 ° C. as shown in FIG.
Thereby, as shown in FIG. 3, the shutter blade 4 is driven in the opening direction against the closing spring 9, and the shutter blade 4 is rotated to the open position.
[0022]
In FIG. 6, the charging of the capacitor C1 proceeds with time with a current determined by the subject luminance, and when the capacitor C1 is charged to the reference potential divided by the resistors R1 and R2, the output of the comparator COMP becomes HIGH.
Thereby, the holding magnet Mg14 is turned off and the latch is released.
At this time, as shown in FIG. 4, the rotating lever 13 becomes free, and the biasing force of the auxiliary spring 16 is sufficiently weaker than the biasing force of the closing spring 9, so that the shutter blade 4 is driven to the closed position and the shutter is closed.
At the same time that the holding magnet 14 is turned off, the energization of the fibrous shape memory alloy 8 is also turned off. Therefore, the fibrous shape memory alloy 8 is relaxed and extended by heat radiation, and the rotating lever 13 is held again by the biasing force of the auxiliary spring 16. It returns to the position where it abuts on the magnet 14.
The fibrous shape memory alloy 8 contracts when the ambient temperature becomes equal to or higher than the transformation point, other than heat generation by energization.
[0023]
When the fibrous shape memory alloy 8 contracts other than the release operation, the holding magnet 14 is turned off, so that the driving force due to the contraction of the fibrous shape memory alloy 8 pulls the rotating lever 13 away from the holding magnet 14. The shutter blade 4 is not opened. Thereby, inadvertent exposure operation can be prevented.
[0024]
[Second Embodiment]
FIG. 7 shows another embodiment of the latch mechanism 3. Basically, it is the same as the latch mechanism 3 shown in FIG. 1, and corresponding portions are denoted by corresponding reference numbers for easy understanding.
Instead of the holding magnet 14 of the latch mechanism 3, the latch mechanism 3 b is formed by the holding lever 21 and the fibrous shape memory alloy 18.
[0025]
In the latch mechanism 3b shown in FIG. 7, instead of performing the shutter closing operation by turning off the holding magnet 14, the fibrous shape memory alloy 18 provided separately from the blade opening operation is energized and heated. The difference is that the locking by the lever 21 is released.
The fibrous shape memory alloy 18 is also preheated in the first stage of the camera release operation (not shown).
Since the calorific value of the fibrous shape memory alloy 18 is proportional to the supplied power, the electric energy for the preheating temperature obtained in advance may be given by the PWM method.
Since power control by PWM is conventionally known, detailed description is omitted.
[0026]
In the above embodiment, a latch mechanism using a holding magnet and a holding lever is used. However, the present invention is not limited to this, and fixing of a fibrous shape memory alloy that is a driving source of the shutter blades is fixed. Other mechanisms may be used as long as they have a function capable of holding and releasing the state.
Further, the number of shutter blades and the like are arbitrary, and it is needless to say that other specific detailed structures can be appropriately changed.
[0027]
【The invention's effect】
According to the first aspect of the present invention, when the fibrous shape memory alloy contracts other than the release operation, the closed state of the shutter can be maintained by releasing the fixed state of the latch mechanism.
[0028]
According to the invention described in claim 2, the rotating lever can be held by the auxiliary spring so as to contact the latch mechanism except when the fibrous shape memory alloy is unintentionally contracted.
[0029]
According to the fourth aspect of the present invention, the time until the heat shrinkage of the fibrous shape memory alloy can be shortened, and the release time lag can be reduced.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a schematic configuration of a shutter device for illustrating a configuration of an embodiment to which the present invention is applied.
FIG. 2 is a diagram showing a state in which the shutter blades are slightly changed from the latched state shown in FIG. 1 by the first stage of the release operation.
3 is a view showing a state where shutter blades are opened from the state shown in FIG. 2; FIG.
4 is a view immediately after the shutter blades are closed from the state shown in FIG. 3;
FIG. 5 is a diagram showing temperature-strain characteristics of a fibrous shape memory alloy used in the configuration of an embodiment to which the present invention is applied.
6 is a diagram illustrating an example of a control circuit of the shutter device illustrated in FIG. 1. FIG.
FIG. 7 is a schematic configuration diagram showing a latch mechanism of a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Shutter apparatus 2 Shutter part 3 Latch mechanism 3b Latch mechanism 4 Shutter blade 5 Shutter opening part 6 Rotating shaft 7 Electrode A
8 Fibrous shape memory alloy 9 Closing spring 10 Anti-rotation 11 Switch P
12 Blade drive lever 13 Rotating lever 14 Holding magnet 15 Electrode B
16 Auxiliary spring 17 Rotating shaft 18 Fibrous shape memory alloy 19 Electrode 20 Electrode 21 Holding lever 22 Rotating shaft 23 Holding spring 24 Rotation stop

Claims (4)

A closing spring that normally urges the shutter blade in the closing direction on the drive lever of the shutter blade, and one end of a fibrous shape memory alloy that contracts by energization and opens the shutter blade against the urging force of the closing spring; A camera shutter device connected to
A shutter device for a camera, comprising a latch mechanism that holds the other end of the fibrous shape memory alloy in a fixed state during a release operation and releases the hold in the fixed state except during a release operation. A rotating lever that is connected to the other end of the fibrous shape memory alloy with one end connected to the drive lever and is held in a fixed state by the latch mechanism;
The camera shutter device according to claim 1, further comprising: an auxiliary spring connected to the rotation lever and biasing the rotation lever in a direction held by a latch mechanism with a force weaker than that of the closing spring. . 3. The camera shutter device according to claim 1, wherein the latch mechanism is either a holding magnet that attracts the rotating lever or a holding lever that engages with the rotating lever. 4. The camera shutter device according to any one of claims 1 to 3, further comprising control means for energizing and preheating the fibrous shape memory alloy in a first stage of a release operation.

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