JPH02256034A - Camera provided with electromagnetic-driven shutter - Google Patents

Abstract

PURPOSE:To prevent the effect of the variation of a power supply on an actuator by providing a voltage discrimination means and a pulse forming means which sets the duty ratio of a pulse whose effective current is made constant and driving the actuator with the aid of the pulse outputted from the pulse forming means. CONSTITUTION:The camera is provided with the voltage discrimination means 102-A for detecting the voltage level of the power-supply voltage and the pulse forming means 102-D which sets the duty ratio of the pulse whose effective current is made constant on the basis of voltage information from the voltage discrimination means 102-A. The actuator for shutter 101 is allowed to be driven with the aid of the pulse outputted from the pulse forming means 102-D. Thus, the effect of the variation of the power-supply voltage is prevented and exposure control with high accuracy is accomplished with the simple constitution of a circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a camera equipped with an electromagnetically driven shutter device.

[Conventional technology]

Electromagnetic devices R (hereinafter referred to as actuators) that are driven by electromagnetic force can be driven and controlled by changing the current flow time, current amount, or current direction, and are generally simple in structure, so they are not electrified. It is often used in devices that require driving force and complex control, such as camera shutter devices and photographic lens drive devices.

However, the advantage that the strength of electromagnetic force is proportional to the amount of current is that if the power source is a battery, such as in a camera, the required current cannot always be supplied to the actuator because the voltage of the battery decreases over time as it is used. This causes the electromagnetic force that is generated to change, which is a disadvantage in that it becomes an obstacle to accurate operation.

Therefore, two ways to prevent the above-mentioned disadvantages due to power supply voltage fluctuations are generally to connect a constant voltage circuit between the power supply and the actuator and use the stable output voltage of the constant voltage circuit; There is a method of changing the energization time or a method of changing the amount of energization current.

When using a constant voltage circuit, the problem of energy conservation arises especially when the power source is a battery because the constant voltage involves power loss in the power supply, and considering the voltage drop over time, Therefore, it is necessary to set the supply voltage to the actuator at a low level, which prevents effective use of the power source, and has the disadvantage that the circuit configuration becomes complicated.

When changing the energization time, as the power supply voltage decreases, the actuator's driving force also decreases, so the actuator's driving energy decreases and the operation becomes unstable due to friction loss during operation. However, the rebound condition changes when sudden braking is performed, and the operating speed is also slower, so control is required to perform secondary corrections such as advancing the start time of the brake. There is.

When changing the amount of current, a circuit is required to change the constant voltage output of the constant voltage circuit described above in multiple stages, which has the disadvantage that the circuit configuration becomes even more complicated and requires complicated control. Moreover, it has the disadvantage that it is difficult to make minute corrections for changes in the actuator's operating speed due to changes in the amount of current.

There have been several methods to prevent actuator power fluctuations, but all of them have some drawbacks. Because of the ease of control in consideration of the above, an energization time control method is often used, as shown in Japanese Patent Laid-Open No. 110431/1983. This will be further explained in detail by giving an example in which an actuator is used in a camera shutter device.

FIG. 1 shows, as an example, a monostable high-speed control solenoid used as an actuator for such a shutter device, and its configuration includes a permanent magnet 30D and adjacent coils 30C and 30G that swing in a bobbin. It consists of a movable iron core 30A that can be housed in a movable iron core 30A, and a movable member 30B that is attached to the tip of the movable iron core 30A.

When the coil 30G is not energized, the movable iron core 30A is attracted to the permanent magnet 30D and the movable member 30B is in the first position shown in the figure, but when the coil 30C is energized, the electromagnetic force is Depending on the direction of the current, the current may act in the same direction as the attractive force of the permanent magnet 30D, or may act in a direction that cancels out the attractive force of the permanent magnet 30D. In the latter case, when the energizing current exceeds a certain level, a driving force exceeding the attractive force of the permanent magnet 300 is generated, and the movable member 30B rotates counterclockwise around the support shaft '30F to the first position shown in the figure. to the second position shown opposite.

Next, when the power to the coil 30C is cut off, the movable member 30B
Return to the first position again. Note that from now on, the description will be limited to the case where electricity is applied so that the electromagnetic force of the coil 30c acts in a direction to cancel the attractive force of the permanent magnet 300.

Therefore, the drive bin 3 protruding from the movable member 30B
When the pulley 30C is energized by fitting the coil 30C into the elongated hole of the shutter blade, the shutter blade can be opened and closed.
It can be seen that it is variable depending on the energization time to C.

Since this actuator operates reliably and at high speed, it can be expected to operate reliably when used in a shutter device, and the opening speed of the shutter can be expected to be faster than conventional shutters, which is advantageous in terms of shutter efficiency.

Especially when the shutter blades are driven directly by the actuator and the blades are made of synthetic resin, the load on the solenoid is very small.
This is even more advantageous in terms of power saving.

A description will be given based on a camera diaphragm/shutter device in which the monostable high-speed control solenoid described above is used as an actuator. Figure 2 shows the mechanism diagram, and Figure 7
The figure shows an example of the aperture characteristics of the shutter, with the vertical axis representing the aperture diameter and the horizontal axis representing the elapsed time after the start of energization of the actuator. In the figure, curves A, B, C, and D indicate that the energization time is increased in the order, and tB indicates the energization time corresponding to curve B.

It can be seen from Figure 7 that the amount of exposure changes when the energization time is changed, but the exposure characteristics are shown by taking the subject brightness corresponding to the exposure amount of the shutter device on the vertical axis and the energization time on the horizontal axis. is curve A in FIG. However, the subject brightness was expressed as an EV value.

As can be seen from the curve in FIG. 8, if the energization time is increased, the amount of exposure increases and corresponds to low luminance, but the slope of the curve is gentle. On the other hand, in a region corresponding to high brightness with a short energization time, the change in exposure amount with respect to the energization time is extremely large, making it difficult to make the characteristics uniform.

Next, a case will be described in which a regulating member for regulating the aperture diameter is provided.

When the energization time is short, the movable member does not reach the position of the regulating member and returns to the first position, so it behaves the same as a shutter device without a regulating member, but as the energization time increases, the length increases. The movable member begins to collide with the regulating member, and the repulsive force generated at this time returns the movable member in the direction of the first position.

So, if we cut off the power at the same time as a collision occurs,
The movable member returns to the first position due to the effects of both the repulsive force due to the collision and the attractive force of the permanent magnet, at a faster speed than when returning due to the effect of the attractive force of the permanent magnet alone.

Next, if the power is cut off just before a collision occurs, the inertia of the movable member at that point will cause the movable member to collide with the regulating member, again at a faster speed than it would have returned solely due to the attraction force of the permanent magnet. Return to first position.

If the power is turned off immediately after a collision occurs, part of the repulsive force due to the collision will be canceled out by the driving force of the coil, but most of it will remain, and most of it will be combined with the attractive force of the permanent magnet. and the repulsive force of the permanent magnet, and returns to the first position at a faster rate than it would return due to the action of the attractive force of the permanent magnet alone.

If the energization time is further increased, the driving force of the coil acts against the repulsive force caused by the collision, the movable member starts moving toward the second position again, and the shutter blade shifts to the opening operation again. .

Depending on the energization time, multiple collisions occur, but the influence of the repulsive force generated by the collisions is not very large at first and gradually decreases.

Note that when the energization time is increased, the amount of exposure increases, so that the impact of collision between the movable member and the regulating member on the amount of exposure becomes smaller.

FIG. 9 shows these situations, and curve B in FIG. 8 shows the relationship between energization time and brightness.

In curve B of FIG. 8, tc is the minimum time for the movable member and the regulating member to collide when energized, and the energization time is tc
When this value is exceeded, a collision occurs and the repulsive force of the collision is added, which shortens the shutter closing time, and as a result, the amount of exposure begins to decrease.

The shutter blades close most quickly when the time when the repulsive force from the collision acts coincides with the time when the electricity is turned off and the attraction force from the permanent magnet begins to act.In this case, the shutter blade is exposed The quantity will be the minimum value in this neighborhood. This energization time is defined as Lm, and when it exceeds Lm, the exposure amount increases again.

In this way, in a shutter device using a monostable high-speed control solenoid, if there is no regulating member, the brightness corresponding to the exposure amount will uniformly decrease depending on the energization time, as shown by curve A in Figure 8. However, if a regulating member is installed,
In a high-brightness region where the energization time is short, a peculiar behavior is exhibited as shown by curve B in FIG.

Figure 1O shows an example of the aperture characteristics of a shutter device that has an aperture mechanism independent of the shutter instead of a regulating member, and shows the relationship between the energization time and subject brightness in that case. This is curve C in FIG.

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

In FIG. 12, the energization operation start timing of curve A is advanced by about 5 ms so that curves A and B in FIG. 11 match.

As is clear from this figure, the peculiar phenomenon caused by the bounce caused by the impact of activating the regulating member at the initial stage of opening of the shutter and colliding with the movable member of the actuator is caused by the difference in driving energy due to the difference in voltage, and is shown in curve A. It can be seen that B is significantly different. Therefore, the exposure characteristic curve cannot be sufficiently corrected by the open control when energized.

[Problem that the invention seeks to solve]

The present invention aims to solve these problems, and provides a camera equipped with an electromagnetically driven shutter that eliminates the influence of power fluctuations on the actuator, prevents loss of drive energy, and operates stably at high speed. It is something.

[Means for solving problems]

The above problem is solved in an electromagnetically driven shutter device that includes an actuator having a movable member driven by electromagnetic force and a shutter blade mechanism that engages with the movable member. The actuator is characterized by comprising a pulse forming means for fully setting the duty ratio of the pulse so that the effective current is constant based on voltage information from the means, and the actuator is driven by the pulse output from the pulse forming means. The problem is solved by a camera equipped with an electromagnetically driven shutter device.

〔Example〕

FIG. 5 shows a shutter control circuit for keeping the effective current constant according to the present invention. (Other circuits such as film winding are not shown) S W r is a main switch, SW is a release switch, Vs is a power supply, Tr, Tr is an actuator for the shutter, a transistor for operating 101, D is a reverse current prevention diode, Rl+Rx is a voltage level detection resistor, and 102 is a microcomputer.

The microcomputer 102 includes a voltage determining means (102-A) having an A/D converter, and a signal forming means (102-A) that outputs pulses based on a pulse duty ratio that keeps the effective current constant.
02-D) Memory means (1) for storing information for setting the duty ratio based on the voltage level, exposure control related information necessary for photography, photographic lens control related information, etc.
02-B) and a CPU (102-C) that selects a pulse duty ratio that makes the effective current constant based on voltage information and controls the sequence of the entire camera.

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

The actuator 101 is the aforementioned monostable high-speed control solenoid. When the main switch SW is closed, the power supply V8
is supplied to the microcomputer 102, the microcomputer 102 becomes operational, and at the same time, the power supply voltage is detected by the voltage determining means (102-A) by the resistors R, , R.

The voltage information detected by the voltage discrimination means (102-A) is C
Output to PU (102-C), CPU (102-C)
is a memory means (102-B) based on the voltage information.
The duty ratio of the pulse that makes the effective current more constant is selected, and the duty ratio setting information of the pulse is transmitted to the signal forming means (1
02-D). Signal forming means (102-D)
will form a pulse based on the setting information.

Then, when the release switch (SWt) is operated,
The CPU (102-c) operates a photometering means and a distance measuring means (not shown) to perform exposure control.

When the shutter open signal is output from the CPU (102-C), the already set pulse is output to the signal forming means (102-D).
) and the transistors T rl and T r2 are 0N.
10FF operates and the actuator (101) starts opening operation.

After the opening operation continues according to the set exposure control program, when the shirt shutter close signal is output, the signal forming means (102-D) stops operating, and at the same time, the transistor T
The energization to r, Tr is cut off, the actuator 101 performs a closing operation, and the exposure control is completed. Thereafter, known operations such as film feeding are performed.

In the explanation 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 explanation, but this information does not include the voltage drop of the power supply at that time. It may be a value, and is not particularly limited as long as it is information that can detect voltage fluctuations.

Furthermore, regarding the setting of the pulse duty ratio, it goes without saying that the relationship between the voltage value and the duty ratio may be made into a table and stored in memory or programmed.

Figure 6(a) shows the effective voltage value (V) when the waveform has a rectangular wave, and Figure 6(b) shows the effective current value (1).However, setting the duty ratio Therefore, it is desirable to avoid methods that require long processing times in order to perform rapid control.

Next, a third embodiment of the shutter device of the present invention will be described.
As shown in the figure. Note that, in FIG. 3, the shutter blade and the shutter blade pressing plate are omitted. For these, please refer to FIG. 2. FIG. 4 is a block circuit diagram of the control section of the shutter device.

FIG. 3 shows two electromagnetic drive members attached to the outer part of the camera shutter device of the present invention.
20A is a shutter base plate constituting the shutter device, 20A is an opening for the photographing optical path, and 30 is a stabilized high-speed control solenoid that is an actuator for driving the shutter blades. , is elastically engaged with and fixedly held by a pair of upper and lower hook members 20B protruding from the hook member 20B.

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

On the other hand, 40 is a regulating member that prevents the movement of one movable member 30B midway, and prevents the movable member 30B from moving from the first position shown in the figure to the second position on the opposite side by energizing the coil 30C. It acts as a stop on the way.

The regulating member 40 is pivotally attached to the shutter base plate 20, and is constantly biased clockwise by a return spring 43. The biased regulating member transmits biasing force to the movable iron core 50B of the plunger solenoid 50 of the regulating member driving actuator, and the biased movable iron core 50B is configured to be locked by the stopper 44.

40A and 40B are both bent portions formed on the regulating member 40, and the bent portion 40A is formed on the movable iron core 50.
B to transmit the biasing force, and the bending portion 40
B is an object with which the movable member 30B collides when the regulating member 40 prevents the movement of the movable member 30B.

23 is a pair of 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 24 is a curved portion provided to determine the opening area according to the rotation angle of the shutter blade 23.

The shutter blade 23 is connected to a shaft 25 that fits into a hole in the shutter base plate 20 and serves as a fulcrum for its rotation, and the movable member 30B.
A long hole 26 into which the drive bottle 30E protruding from the hole 26 is inserted and fitted.
They each have the following. Further, the shutter base plate 20 is provided with an elongated shaft 20C so that the drive bin 30E protruding from the movable member 30B can be moved by the swinging motion of the movable iron core 30A.

On the other hand, the plunger solenoid 50 is controlled to be energized by the control section, but when it is not energized, the movable iron core 50B protrudes to the right as shown in the figure and is stopped at that position by the stopper 44. The regulating member 4
0 is held at the position shown.

When the plunger solenoid 50 is energized, the movable iron core 5
0B is attracted and moves to the left, and the regulating member 40 retreats from the movement locus of the movable member 30B, so the movable iron core 30A
Even if the movable member 30B swings, the structure is such that the movable member 30B does not collide with the bent portion 40B.

When the coil 30C of the stabilized high-speed control solenoid 30 is not energized by the control unit, that is, before the exposure operation, the movable member 30A is held in a stable first position by the attractive force of the permanent magnet 30D. The shutter blade 23 is kept in a closed state by being biased.

In normal photography, the control unit controls the plunger solenoid 5.
0, the regulating member 40 is set in the position shown in FIG. 3, and by energizing the coil 30G, the
When B attempts to move, it collides with the bending portion 41 of the regulating member 40, thereby preventing the movable member 30B from moving to the second position.

Then, the above-mentioned peculiar phenomenon occurs, resulting in exposure characteristics that are advantageous for high-brightness regions, so that appropriate exposure can be achieved by setting the energization time for the coil 30G.

On the other hand, if the subject is in low brightness, you can simply set the energization time to a long time to match the low brightness, but if the exposure time is too long, the photographer's camera shake will have an adverse effect, so it is recommended to shorten the time. It's better.

In such a case, the plunger solenoid 50 is energized by a signal from the control section to attract the movable iron core 50B to the left. Then, the regulating member 40 rotates counterclockwise against the return spring 43, and the bending portion 40
B retreats from within the movement trajectory of the movable member 30B, and then when the coil 30G of the monostable high-speed control solenoid 30 is energized, the movable member 30B moves from the first position to the second position. Then, the drive pin 30E drives the shutter blade 23 and rotates until the shutter blade 23 is fully opened, the opening 2OA acts as a diaphragm to perform exposure, and the end of energization is again caused by the attraction force of the permanent magnet 300 to close the first Return to position and finish exposure.

Therefore, since the shutter blades are fully open when the regulating member is not used to regulate the exposure, the current application time may be short to obtain the same amount of exposure.

In the shutter device described so far, when the plunger solenoid 50 is energized, the bending portion of the regulating member 40
40B retreats from the movement locus of the movable member 30B, and even if the movable iron core 30A swings, the movable member 30B moves away from the bending portion 4.
The structure is such that it does not collide with 0B. However, without providing the plunger solenoid 50, the regulating member 40 is
0B, and while the movable member 30B is moving from the first position force to the second position direction, the movable member 30B
It is also possible to adopt a structure that always collides with the regulating member 40.

Furthermore, with the shutter device of the present invention, for example, when the subject brightness is high or medium, exposure accuracy is ensured by utilizing the collision phenomenon described above, and when the subject brightness is low, exposure accuracy is ensured without using the collision phenomenon. You can also. If you want to do that, plunger solenoid 5
0, a regulating member driving means having three types of stop positions is provided, and a regulating member 40 is provided in the operating portion of the regulating member driving means.
The bending portion 40A is engaged so that the regulating member 40 pivoted to the shutter base plate 20 swings and stops at the three positions described above.

When the regulating member driving means moves to any position and stops in response to a signal from the control section, the regulating member 40 pivoted to the shutter base plate 20 also rotates, and the two types of collision parts provided on the bending part 40B rotate. Either one of them collides with the movable member 30B, or the regulating member 40 retreats from the movement locus of the movable member 30B, so that the bending portion 40B and the movable member 30B do not collide. Similarly, if it is desired to further increase the number of exposure adjustment steps, the number of stop positions and types of collision portions described above may be further increased.

Further, the shutter device of the present invention has the following modifications, and in each case, the exposure accuracy is improved by utilizing the effect corresponding to the collision between the movable member 30B and the bent portion 40B.
The special J is the same in that it ensures exposure accuracy for high-brightness subjects.

In the shutter device described above, the swinging motion of the movable iron core 3OA 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 causing the shutter blade to open and close. However, there are many shutter devices that have a structure in which a separately provided shutter blade driving member is interposed between the actuator and the shutter blade, and the movement of the actuator is transmitted 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, the shutter blade driving member performs a rotational reciprocating motion, a linear reciprocating motion, etc. following the swinging of the movable member 30B, and the shutter blade is driven. The shutter blades open and close in accordance with the movement of the members.

In this case, even if the regulating member collides with the shutter blade driving member, the same effect can be obtained. moreover,
The regulating member can be evacuated from the collision position or caused to collide with any one of a plurality of collision positions using the same means as described above. In addition, in the description up to this point, a shutter device is described in which a plurality of collision parts are provided on the side of the regulating member, but the collision part of the regulating member is provided at one place, and the collision part of the regulating member is provided at one place, for example, on the movable member 30B of the movable iron core 30A or the shutter device. A plurality of collision parts are provided in a corresponding part of the blade drive member,
A structure may be adopted in which the collision position can be selected by the regulating member driving means.

[Effects of the Invention] The present invention makes it possible to operate the actuator with stable drive energy without being affected by fluctuations in power supply voltage, making it possible to achieve high-precision exposure control with a simple circuit configuration. .

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a monostable high-speed control solenoid. Figure 2 is a mechanical diagram of an aperture and shutter device using a monostable high-speed control solenoid. FIG. 3 is a mechanical diagram showing an embodiment of the shutter device of the present invention. FIG. 4 is a block circuit diagram of the control section 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 the effective voltage value and effective current value in a rectangular wave, respectively. FIG. 7 is a graph showing an example of energization time and shutter opening characteristics. FIG. 8 is a graph showing the relationship between subject brightness and energization time. FIGS. 9 and 10 are graphs showing the relationship between current application time and aperture diameter. FIGS. 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 3OA... Movable iron core 30B... Movable member 30G... Coil 30D. ...Permanent magnet 30E...Drive bin 40...Restriction member 44...Stopper 50...Plunger solenoid

Claims (1)

[Claims] In an electromagnetically driven shutter device comprising an actuator having a movable member driven by electromagnetic force and a shutter blade mechanism engaging the movable member, a voltage discriminating means for detecting a voltage level of a power supply voltage and a voltage from the voltage discriminating means are provided. and a pulse forming means for setting a duty ratio of a pulse such that an effective current is constant based on information, and the actuator is driven by a pulse output from the pulse forming means. equipped camera.