JP2843866B2 - Camera with electromagnetically driven shutter - Google Patents

Description

The present invention relates to a camera provided with an electromagnetically driven shutter device.

[Conventional technology]

Electromagnetic devices driven by electromagnetic force (hereinafter referred to as actuators) can be driven and controlled by changing the time and amount of current flow, or the direction of the current, and are generally electrified because of their simple structure. It is widely used in devices requiring a driving force and requiring complicated control, such as a shutter device of a camera and a photographing lens driving device.

However, the advantage that the strength of the electromagnetic force is proportional to the amount of current is that when the power source is a battery such as a camera, the necessary current cannot always be supplied to the actuator because the battery voltage decreases over time as it is used. In this case, the generated electromagnetic force changes, which is also a disadvantage of causing an injury for performing an accurate operation.

Therefore, as a method of preventing the above-mentioned drawbacks due to fluctuations in the power supply voltage, generally, a constant voltage circuit is connected between the power supply and the actuator and a stable output voltage of the constant voltage circuit is used. There is a method of changing the energizing time or a method of changing the amount of energizing current.

When a constant voltage circuit is used, there is a problem of energy saving especially when the power supply is a battery because the power supply of the power supply is lost in order to make the voltage constant. Therefore, it is necessary to set the supply voltage to the actuator low, and there is a drawback that an effective power supply cannot be used and the circuit configuration becomes complicated.

When the energization time is changed, the driving power of the actuator also decreases as the power supply voltage decreases, so that the driving energy of the actuator decreases and the operation becomes unstable due to the influence of friction loss during operation, etc. However, there is a disadvantage that a control for performing a secondary correction is required, such as a change in a rebound state when sudden braking is performed, and an earlier operation start time because the operation speed is slower.

When the amount of current is changed, a circuit for changing the constant voltage output of the constant voltage circuit into a plurality of stages is required, which has a drawback that the circuit configuration becomes more complicated and complicated control is required. In addition, there is a disadvantage that fine correction of a change in the operating speed of the actuator due to a change in the amount of current becomes difficult.

Although there were several methods for preventing such power fluctuations of the actuator, all of them had some disadvantages. However, when applied to a camera, simplicity of the circuit configuration and variations in the operation of each actuator were required. Because of the easiness of control in consideration of the above, the energization time control method is often used as seen in JP-A-63-110431. An example in which an actuator is used for a shutter device of a camera will be described in further detail.

FIG. 1 shows, as an example, a monostable high-speed control solenoid that is used as an actuator of such a shutter device, and has a structure in which a permanent magnet 30D, a coil 30C adjacent thereto and a bobbin of the coil 30C are swung. The movable iron core 30A includes a movable member 30B attached to the tip of the movable iron core 30A.

When power is not supplied to coil 30C, movable iron core 3
0A is attracted to the permanent magnet 30D, and the movable member 30B is
When the coil 30C is energized, its electromagnetic force acts in the same direction as the attraction force of the permanent magnet 30D depending on the direction of the current, and when it acts in the direction to cancel the attraction force of the permanent magnet 30D. There is. In the latter case, when the energizing current exceeds a certain level, a driving force exceeding the attraction force of the permanent magnet 30D is generated, and the movable member 30B rotates counterclockwise around the support shaft 30F and moves to the first position shown in the drawing. The second illustrated opposite
To the position.

Next, when the current supply to the coil 30C is stopped, the movable member 30B returns to the first position again. Note that the description will be limited to the case where current is supplied such that the electromagnetic force of the coil 30C acts in a direction to cancel the attractive force of the permanent magnet 30D.

Therefore, by energizing the coil 30C by means such as fitting the drive pin 30E protruding from the movable member 30B into the long hole of the shutter blade, the shutter blade can be opened and closed, and the exposure amount at that time is It can be seen that it becomes variable depending on the current supply time to the coil 30C.

This actuator is reliable and fast,
When used in a shutter device, reliable operation can be expected, and the opening speed of the shutter can be expected to be faster than in the past and advantageous in terms of shutter efficiency.

In particular, in the case where the shutter blades are driven directly by the actuator and the blades are made of synthetic resin, the load on the solenoid becomes very small, which is further advantageous for power saving.

A description will be given based on a camera diaphragm / shutter device when the above-mentioned monostable high-speed control solenoid is used as an actuator. FIG. 2 shows the mechanism diagram, and FIG. 7 shows an example of the aperture characteristic of the shutter, in which the vertical axis represents the aperture diameter and the horizontal axis represents the elapsed time after the energization of the actuator is started. In the drawing, it is shown that the energization time is lengthened in the order of the curves A, B, C, and D. tB indicates the energization time corresponding to the curve B.

It can be seen from FIG. 7 that the exposure amount changes when the energizing time is changed. The exposure characteristic is shown by taking the subject luminance corresponding to the exposure amount of the shutter device on the vertical axis and energizing time on the horizontal axis. Is the curve A in FIG. However, the subject brightness was represented by an EV value.

As can be seen from the curve A in FIG. 8, when the energization time is lengthened, the exposure amount increases to correspond to low luminance, but the slope of the curve is gentle. On the other hand, an area corresponding to a high luminance with a short energization time is an area where the change in the exposure amount with respect to the energization time is extremely large and it is difficult to make the characteristics uniform.

Next, a case where a regulating member for regulating the aperture diameter of the diaphragm is provided will be described.

While the energizing time is short, the movable member returns to the first position without reaching the position of the regulating member. Therefore, the movable member behaves in the same manner as a shutter device without the regulating member. Therefore, the movable member starts to collide with the regulating member, and the movable member is returned in the direction of the first position by the repulsive force generated at that time.

Therefore, assuming that the power supply is cut off at the same time as when the collision occurs, the movable member is moved to the first position at a faster speed than both the rebound force by the collision and the attraction force of the permanent magnet. Return to

When the power is turned off immediately before the next collision occurs, the movable member collides with the regulating member due to the inertia of the movable member at that time, and also at a faster speed than the return by only the attraction of the permanent magnet. Return to the first position.

If the power is turned off immediately after the collision occurs, a part of the repulsive action of the collision is offset by the action of the driving force of the coil, but most of the action remains and the attractive force of the permanent magnet and the Both act to return to the first position at a faster rate than return by the action of only the attractive force of the permanent magnet.

If the energizing time is further extended, the driving force of the coil acts against the action of the repulsive force due to the collision, and the movable member
The shutter blade starts moving toward the second position again, and the shutter blade shifts to the opening operation again.

Depending on the energization time, a plurality of collisions occur, but the effect of the repulsive force generated by the collision is not as large as the first collision and gradually decreases.

If the energization time is lengthened, the exposure amount increases, so that the impact of the collision between the movable member and the regulating member on the exposure amount decreases.

FIG. 9 shows these states, and curve B in FIG. 8 shows the relationship between the energizing time and the luminance.

In the curve B in FIG. 8, tc is the minimum time during which the movable member and the regulating member collide when energized. When the energized time exceeds tc, a collision occurs and a repulsive force of the collision is applied to shorten the shutter closing time. As a result, the exposure starts to decrease.

When the timing at which the repulsive force due to the collision acts and the timing at which the energization is cut off and the attraction force by the permanent magnet begins to act coincide with each other, the shutter blades perform the closing operation at the fastest speed. The quantity has a minimum value in this vicinity. When the energizing time is tm and exceeds tm, the amount of exposure starts to increase again.

As described above, in the shutter device using the monostable high-speed control solenoid, when there is no regulating member, the luminance corresponding to the exposure amount is uniformly reduced as shown in the curve A of FIG. However, when the regulating member is provided, it exhibits a peculiar behavior as shown by a curve B in FIG.

FIG. 10 shows an example of an aperture characteristic of a shutter device provided with an aperture mechanism independent of a shutter instead of providing a regulating member, and shows a relationship between an energizing time and subject brightness in that case. This is curve C in FIG.

FIG. 11 shows an exposure characteristic curve when the supply voltage to the actuator changes, and it can be seen that curves A and B do not match.

FIG. 12 is a diagram in which the energization operation start timing of curve A is advanced by 5 ms so that curves A and B in FIG. 11 coincide. As is apparent from this figure, the peculiar phenomenon due to the bounce caused by the operation of the restricting member at the initial stage of the shutter opening and the collision with the movable member of the actuator becomes a difference in driving energy due to a voltage difference and a curve A. It can be seen that B is greatly different. Therefore, in the energization opening control, a sufficient correction of the exposure characteristic curve cannot be obtained.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION The present invention is directed to solving such a problem, and provides a camera having an electromagnetically driven shutter that operates stably at high speed while eliminating the influence of power supply fluctuation on the actuator and preventing loss of driving energy. Things.

[Means for solving the problem]

In an electromagnetically driven shutter device including an actuator having a movable member driven by an electromagnetic force and a shutter blade mechanism engaged with the movable member, a voltage discriminating means for detecting a voltage level of a power supply voltage; Memory means for storing a duty ratio of a pulse at which the effective current becomes constant in correspondence with the pulse current generation means, and pulse forming means for setting a duty ratio of the pulse. A pulse duty ratio selected by the memory means based on the voltage level from the pulse generator, and the actuator is driven by a pulse output from the pulse forming means at the duty ratio of the selected pulse. The problem is solved by a camera having a shutter device.

〔Example〕

FIG. 5 shows a shutter control circuit for keeping the effective current constant according to the present invention. (Film other circuits such as the winding is not shown) SW ₁ is a main switch, SW ₂ is a release switch, V _B power supply, Tr _1, Tr ₂ are actuators for shutters, transistors for operating the 101, D Is a backflow prevention diode, R ₁ and R ₂ are voltage level detection resistors, and 102 is a microcomputer.

The microcomputer 102 has a voltage discriminating means (102-A) having an A / D converter, and a signal forming means (102-A) for outputting a pulse based on the duty ratio of the pulse for keeping the effective current constant.
D) Memory means (102-) for storing information for setting a duty ratio according to a voltage level, exposure control-related information necessary for photographing, photographing lens control-related information, and the like.
B) and a CPU (102-C) for selecting the duty ratio of the pulse at which the effective current is constant based on the voltage information and controlling the sequence of the entire camera.

 Next, the operation of the above circuit will be described.

The actuator 101 is the above-mentioned monostable high-speed control solenoid. When closing the main switch SW ₁ power V _B is supplied to the microcomputer 102, the microcomputer 102 becomes operation state,
At the same time, the power supply voltage is determined by the resistors R ₁ and R ₂ by the voltage determination means (102−
A) is detected.

The voltage information detected by the voltage determination means (102-A) is
(102-C), the CPU (102-C) selects the duty ratio of the pulse at which the effective current is constant from the memory means (102-B) based on the voltage information, and sets the duty ratio of the pulse. The information is output to the signal forming means (102-D). The signal forming means (102-D) forms a pulse based on the setting information. Therefore the release switch (SW ₂₎ is operated, the CPU (102-C),
Exposure control is performed by operating the photometric means and the distance measuring means (not shown).

Opens CPU (102-C) when the shutter open signal is outputted pulses already been set is outputted from the signal forming means (102-D) from the transistor Tr _1, Tr ₂ is ON / OFF operated by actuator (101) Start operation.

After the opening operation is connected by the set exposure control program and the shutter closing signal is output, the operation of the signal forming means (102-D) stops, and at the same time, the transistor T
The energization to r ₁ and Tr ₂ is cut off, the actuator 101 closes, and the exposure control is completed. Thereafter, known operations such as film feeding are performed.

In the description of the operation of the circuit, the information detected by the voltage determining means (102-A) is simply referred to as voltage information in order to simplify the description. The information may be a value, and is not particularly limited as long as the information can detect a voltage fluctuation state.

Also, regarding the setting of the pulse duty ratio, the relationship between the voltage value and the duty ratio is tabulated and stored,
Needless to say, it may be programmed.

FIG. 6 (a) shows an effective voltage value (V ') in the case of having a rectangular wave, and FIG. 6 (b) shows an effective current value (I). However, it is desirable to avoid the method of increasing the processing time for setting the duty ratio in order to perform quick control.

Next, one embodiment in which the shutter device of the present invention is used is shown in FIG. FIG. 3 omits the shutter blades and the shutter blade holding plate. For these, the second
See the figure. FIG. 4 is a block circuit diagram of a control unit of the shutter device.

FIG. 3 shows two electromagnetic driving members to which the outer part of the camera shutter device of the present invention can be attached.
Is a shutter base plate that constitutes a shutter device, 20A is an opening for an optical path for photographing, 30 is a monostable high-speed control solenoid that is an actuator for driving shutter blades, and the monostable high-speed control solenoid 30 is the shutter base plate 20. On the other hand, the hook member 20B is elastically engaged with the pair of upper and lower hook members 20B projecting therefrom and fixedly held.

30C in the monostable high-speed control solenoid 30 is:
A coil for obtaining a driving force by energization, 30A is a movable iron core swingably supported in a bobbin of the coil 30C, 30B is a movable member provided at the tip of the movable iron core 30A,
Further, reference numeral 30D is a permanent magnet serving as a biasing means for the movable iron core 30A.

On the other hand, reference numeral 40 denotes a regulating member for preventing the movement of the movable member 30B in the middle, and the movable member 3 is provided by energizing the coil 30C.
This serves to prevent OB from moving from the first position to the second position on the way.

The regulating member 40 is axially mounted on the shutter base plate 20 and is constantly urged clockwise by a return spring 43. The urged regulating member transmits an urging force to the movable iron core 50B of the plunger solenoid 50 of the regulating member driving actuator, and the urged movable iron core 50B is engaged with the stopper 44.

40A and 40B are bent portions formed on the regulating member 40, the bent portion 40A engages with the movable iron core 50B to transmit the urging force, and the bent portion 40B
0 is a target to which the movable member 30B collides when the movement of the movable member 30B is prevented.

Reference numeral 23 denotes a pair of left-right symmetrical shutter blades housed in a slit-shaped space formed between the shutter blade holding plate 21 fixed to the shutter base plate 20 by screws and the shutter base plate 20, Reference numeral 24 denotes a curved portion provided to determine the opening area of the shutter blade 23 in accordance with the rotation angle. The shutter blade 23 is provided on the shutter base plate 20.
The shaft 25 which is fitted into the hole and serves as a fulcrum of its rotation, and the elongated hole 26 which is fitted by inserting the drive pin 30E drilled in the movable member 30B.
And each is provided. In addition, the shutter base plate 20 includes
An elongated hole 20C is provided so that the drive pin 30E protruding from the movable member 30B can be moved by the swing of the movable iron core 30A.

On the other hand, the energization of the plunger solenoid 50 is controlled by the control unit, but when the energization is not performed, the movable iron core 50B protrudes rightward as shown in the figure, and is locked by the stopper 44 at that position. The regulating member 40 is held at a position shown in the figure.

When the plunger solenoid 50 is energized, the movable iron core 50
B is sucked and moves to the left, and the regulating member 40 is moved to the movable member 30B.
Therefore, even if the movable iron core 30A swings, the movable member 30B does not collide with the bent portion 40B.

When power is not supplied to the coil 30C of the monostable high-speed control solenoid 30 by the control unit, that is, in a state before the exposure operation, the movable member 30A is
The shutter blade 23 is biased and held at the stable first position by the suction force of 0D, and keeps the shutter blade 23 in the closed state.

In normal shooting, the control unit is the plunger solenoid
3, the regulating member 40 is set to the position shown in FIG. 3, and when the movable member 30B attempts to move by energizing the coil 30C, the movable member 30B collides with the bent portion 41 of the regulating member 40 and the movable member 30B moves. Movement of 30B to the second position is prevented.

Then, the above-described peculiar phenomenon occurs, and the exposure characteristic becomes advantageous in a high luminance region. Therefore, appropriate exposure is performed by setting the energizing time to the coil 30C. On the other hand, if the subject has low brightness, only the energization time should be set to a long time according to the low brightness, but if the exposure time is long, the camera shake of the photographer can be adversely affected. Better.

In such a case, the plunger solenoid 50 is energized by a signal from the control unit to cause the movable iron core 50B to be sucked leftward. Then, the regulating member 40 rotates counterclockwise against the return spring 43, and the bent portion 40B retreats from the movement trajectory of the movable member 30B, after which the coil of the monostable high-speed control solenoid 30 When energizing 30C,
The movable member 30B moves from the first position to the second position, and the drive pin 30E rotates until the drive blade 30E is fully opened by driving the shutter blade 23, and the opening 20A acts as a diaphragm to perform exposure. When the power is turned off, the permanent magnet
It returns to the first position by the suction force of 30D, and the exposure is completed.

Therefore, when not regulated by the regulating member, the shutter blades are fully opened, and the energizing time for obtaining the same exposure amount may be short.

In the shutter device described above, when the plunger solenoid 50 is energized, the bent portion 40B of the regulating member 40 retreats from the movement locus of the movable member 30B, and the movable member 30B is bent even if the movable iron core 30A swings. The structure does not collide with the part 40B. However, without providing the plunger solenoid 50, the regulating member 40 is fixed in the movement locus of the movable member 30B,
A structure may be employed in which the movable member 30B always collides with the regulating member 40 while the movable member 30B moves from the first position to the second position.

Further, with the shutter device of the present invention, for example, when the subject brightness is high and medium, the exposure accuracy is ensured using the above-described collision phenomenon, and when the subject brightness is low, the exposure accuracy is ensured without using the collision phenomenon. You can also. If you want to do that, plunger solenoid
Instead of 50, a regulating member driving means having three kinds of stop positions is provided, and a bent portion 40A of the regulating member 40 is engaged with an operating portion of the regulating member driving means, so that the regulating member is pivotally mounted on the shutter base plate 20. The member 40 swings and stops at the above three positions.

When the regulating member driving means moves to any position and stops in response to a signal from the control unit, the regulating member 40 pivotally attached to the shutter base plate 20 also rotates, and is provided on the bent portion 40B.
Any one of the collision portions may collide with the movable member 30B, or the restricting member 40 may be retracted from the movement locus of the movable member 30B so that the bent portion 40B and the movable member 30B do not collide. Similarly, when it is desired to further increase the number of steps of adjusting the exposure amount, the stop positions and the types of the collision portions may be further increased.

Further, the shutter device of the present invention has the following modifications. In any case, the exposure accuracy, particularly the exposure for a high-brightness subject, is exploited by utilizing the effect equivalent to the collision between the movable member 30B and the bent portion 40B. It is the same in terms of ensuring accuracy.

In the above-described shutter device, the swing of the movable iron core 30A of the monostable high-speed control solenoid 30 is transmitted to the shutter blade through the drive pin 30E protruding from the movable member 30B, thereby performing the opening / closing operation. However, there are many shutter devices having a structure in which a separately provided shutter blade driving member is interposed between the actuator and the shutter blade to transmit the motion of the actuator to the shutter blade through the shutter blade driving member.

In such a shutter device, when a monostable high-speed control solenoid is used as an actuator, for example, the shutter blade driving member performs a rotary reciprocating motion, a linear reciprocating motion, etc., following the swing of the movable member 30B, and the shutter blade driving is performed. The shutter blades open and close according to the movement of the member.

In this case, even if the regulating member collides with the shutter blade driving member, the same effect can be obtained. Further, the restricting member can retreat from the collision position or collide at any one of the plurality of collision positions by the same means as described above. Further, in the description so far, the shutter device in which a plurality of collision portions are provided on the side of the regulating member has been described. However, the collision portion of the regulating member is provided in one place, for example, the movable member 30B of the movable iron core 30A or the shutter. A plurality of collision portions are provided in a portion corresponding to this of the blade drive member,
The structure may be such that the collision position can be selected by the regulating member driving means.

〔The invention's effect〕

According to the present invention, the actuator can be operated with stable driving energy without being affected by the fluctuation of the power supply voltage, so that highly accurate exposure control can be realized with a simple circuit configuration.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a monostable high-speed control solenoid. FIG. 2 is a mechanism diagram of an aperture / shutter device using a monostable high-speed control solenoid. FIG. 3 is a mechanism diagram showing an embodiment of the shutter device of the present invention. FIG. 4 is a block circuit diagram of a control unit of the shutter device of the present invention. FIG. 5 is a circuit diagram showing an embodiment of the shutter control circuit of the present invention. FIGS. 6 (a) and 6 (b) show an effective voltage value and an effective current value in a rectangular wave, respectively. FIG. 7 is a graph showing an example of an energizing time and a shutter opening characteristic. FIG. 8 is a graph showing the relationship between subject brightness and energization time. 9 and 10 are graphs showing the relationship between the energizing time and the opening diameter. 11 and 12 are graphs showing exposure characteristic curves when the supply voltage changes. 20 Shutter base plate 21 Shutter blade holding plate 23 Shutter blade 30 Monostable high-speed control solenoid 30A Movable iron core, 30B Movable member 30C Coil, 30D Permanent magnet 30E … Drive pin, 40… regulating member 44… stopper 50… plunger solenoid

Claims (1)

(57) [Claims] 1. An electromagnetically driven shutter device comprising an actuator having a movable member driven by an electromagnetic force and a shutter blade mechanism engaged with the movable member, a voltage discriminating means for detecting a voltage level of a power supply voltage, Memory means for storing a duty ratio of a pulse at which the effective current becomes constant in accordance with the level; and pulse forming means for setting a duty ratio of the pulse. Prior to the operation of the actuator, the control unit performs the voltage discrimination. The pulse duty ratio is selected by the memory means based on the voltage level from the means, and the actuator is driven by a pulse output from the pulse forming means at the selected pulse duty ratio. Camera with drive shutter.