JPH06110106A - Shutter driving device using stepping motor as drive source - Google Patents

Abstract

PURPOSE:To prevent the error of a shutter opening characteristic and the consumption of power at the time of exposing for a long time in a shutter driving device using a stepping motor as a drive source. CONSTITUTION:The driving currents of coils 3a and 3b are changed over according to the pulse of a driving circuit 10 to turn a driving ring 2 to the right. In this process, when cam edges 2a and 2c pass through a cam follower 6b, a lever 6 is turned to the right and a blade 5 is opened (a)-output and (b)-output of a counter 25 are successively raised before and after the blade is opened, and in this time a comparator 20 interrupts the driving current by the generated pulse. The level of a reference power source 22 is changed so as to offset various kinds of fluctuation factors in an opening characteristic so that the duty of the driving current is controlled and the opening characteristic is stabilized. Moreover, when the driving current is interrupted like the pulse at the time of exposing for a long time, the consumption of the power is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shutter driving device using a step motor as a driving source, and more particularly to a shutter driving device for preventing errors in shutter opening characteristics and power consumption during long-time exposure. .

[0002]

2. Description of the Related Art Conventionally, various shutter drive devices have been known in which a shutter is driven to be opened and closed by using a step motor as a drive source. Typical examples thereof are a blade member for opening and closing an exposure opening, and the blade. A blade opening / closing member urged in the direction of opening the member, a step motor capable of forward / reverse rotation, and a portion which is gear-connected to the step motor and drives the blade opening / closing member in the blade opening direction and the blade closing direction. A drive member that is formed, drives the blade opening / closing member in the blade opening direction by the operation of the drive member during the first rotation of the step motor, and drives the blade opening / closing member in the second direction of the step motor after a predetermined time elapses. A device is known in which the blade opening / closing member is driven in the blade closing direction by the operation of the driving member during rotation.

[0003]

When the shutter-related member is driven by using the step motor as a drive source, the design performance can be obtained when the balance between the motor torque and the load is as designed at the time of design. Needless to say. However, there is no guarantee that the balance between motor torque and load will be as designed at the time of design in all products due to individual differences in individual products such as motor resistance errors and load errors. In addition, motors for cameras generally rely on dry batteries for power supply, and it is also possible to avoid fluctuations in motor torque during use due to fluctuations in power supply voltage due to power consumption and reductions in power supply voltage during cold weather. I can't. In addition, the camera is not always used in a horizontal state, and the camera posture changes variously such as bird's-eye view shooting, elevation angle shooting, vertical position shooting, horizontal position shooting, etc. It is also extremely difficult to remove in practice. When the balance between the motor torque and the load is lost due to these factors, there is a problem in that the blade opening characteristic fluctuates due to the speed difference of the driving member particularly near the timing of opening the blade release. is there. There is also a great demand to reduce the consumption of the power source that causes the reduction of the motor torque, especially the significant consumption of the power source during long-time exposure, as much as possible.

[0004]

The present invention has been made in view of such problems and demands, and maintains the balance between the motor torque and the load, stabilizes the opening characteristics of the blades, and is particularly long. It is an object of the present invention to provide a shutter driving device capable of reducing significant power consumption during time exposure.

In summary, a shutter drive device using a step motor as a drive source according to the present invention includes a blade member for opening and closing an exposure opening, a blade opening and closing member biased in a direction of opening the blade member, A step motor capable of rotating in the reverse direction; and a drive member gear-connected to the step motor and having a portion for driving the blade opening / closing member in the blade opening direction and the blade closing direction.
The blade opening / closing member is driven in the blade opening direction by the operation of the driving member during the rotation of the blade, and the blade opening / closing member is moved by the operation of the driving member during the second rotation of the step motor after the elapse of a predetermined time. On the premise of a shutter drive device using a step motor driven in a closing direction as a drive source, it is provided with means for intermittently supplying a motor drive current during the first rotation of the step motor, The above object is achieved by making the duty controllable.

Further, a shutter drive device using a step motor as a drive source according to the present invention is premised on the same shutter drive device as described above: from the end of the first rotation of the step motor to the second rotation. The object is achieved by providing a means for intermittently supplying a motor drive current when the time until the start exceeds a preset time and making it possible to control the duty of the motor drive current.

[0007]

In other words, according to the shutter drive device using the step motor as the drive source of the present invention, the duty of the motor drive current can be controlled in the region that most affects the aperture characteristics of the blades, so that stable aperture characteristics are obtained. It is possible,
In addition, since the drive current can be reduced in a range in which the motor can be stopped and held in a region where the motor drive current is largely consumed, it is possible to reduce the overall power consumption.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a plan view of a shutter drive mechanism according to an embodiment of the present invention. A base plate 1 having an aperture 1a formed in the center has a guide ring 1b on a concentric circle centered on the aperture 1a. The drive ring 2 is supported rotatably along the guide ring 1b.

Further, 3 is a step motor, 3a is an output pinion of the step motor, and the rotation of the output pinion 3a is transmitted to the rack 2a formed on the outer edge of the drive ring 2 via a two-stage gear 4. The ring 2 turns along the guide ring 1b corresponding to the rotation direction of the output pinion 3a.

A shutter blade 5 for opening and closing the aperture 1a is swingably supported on a shaft 1c on the back surface of the shutter blade. Although only the shutter blades 5 are shown in FIG. 1 in order to avoid complication of the drawing, the shaft 1d on the back surface of the main plate 1 has a shutter blade (not shown) which is basically symmetrical to the shutter blades 5 and can swing. Supported by.

A shutter blade 5 is attached to the shaft 1e on the surface of the main plate 1.
An opening / closing lever 6 for driving the opening and closing of
Engagement pin 6a planted near the front end of the opening / closing lever 6
Is an elongated hole 6 formed in the shutter blade 5 through the base plate 1.
When the opening / closing lever 6 is rotated rightward, the engagement pin 6a engages the elongated hole 6a and moves the shutter blade 5 to the shaft 1.
When the aperture 1a is opened by rotating the aperture 1a rightward around the center c and the opening / closing lever 6 is rotated leftward, the engagement pin 6a rotates the shutter blade 5 leftward around the shaft 1c while closing the aperture 1a while engaging the elongated hole 6a. Let

The opening / closing lever 6 is always given a right-handed force (that is, a force in the direction of opening the shutter blade 5) from the spring 7, but in the initial state, the cam follower 6b formed on the opening / closing lever 6 is driven. The cam edge 2b formed on the ring 2 is brought into contact with the ring 2 to suppress right rotation. The drive ring 2 has cam edges 2c, 2d, 2 continuous with the cam edge 2b.
e are sequentially formed, and the cam follower 6b is formed on the cam edge 2
When falling from b to the cam edge 2c, the opening / closing lever 6 rotates clockwise due to the tension of the spring 7, and when the cam follower 6b runs from the cam edge 2c to the cam edge 2e along the cam edge 2d, the opening / closing lever 6 resists the spring 7. Turn left.

Next, FIG. 2 shows an example of a control circuit according to the present invention. Reference numerals 3a and 3b respectively denote A-phase and B-phase coils of the step motor 3, and coils 3a and 3b have a power source VB.
Drive current is supplied from the transistor through the switching transistor. More specifically, the transistor bridge circuit shown in the figure is configured, and for the coil 3a,
A positive drive current is supplied when the transistors T1 and T2 are on, and a negative drive current is supplied when the transistors T3 and T4 are on. A positive drive current is supplied to the coil 3b when the transistors T5 and T6 are on, and a negative drive current is supplied when the transistors T7 and T8 are on.

Next, 10 is a drive circuit for generating positive and negative drive pulses for the A phase and the B phase. A of the drive circuit 10
Phase (positive) pulse is AND gate 11 and inverter 1
It is added to the base of the transistor T1 via 2 and to the base of the transistor T2 via the AND gate 11. The pulse of the A phase (negative, with a bar in the drawing) is the AND gate 13 and the inverter 14.
Via the AND gate 13 to the base of the transistor T3. Similarly, the B-phase (positive) pulse of the drive circuit 10 is applied to the base of the transistor T5 via the AND gate 15 and the inverter 16 and to the base of the transistor T6 via the AND gate 15. A pulse of phase B (negative, indicated by a bar in the drawing) is applied to the base of the transistor T7 via the AND gate 17 and the inverter 18, and applied to the base of the transistor T8 via the AND gate 17. To be

A characteristic of this embodiment is that AND gate 1
The output of the comparator 20 is added to 1, 13, 15, and 17, the output of the sawtooth wave generation circuit 21 is added to the positive phase input of the comparator 20, and the reference power supply 22 is added to the negative phase input of the comparator 20. Levels have been added.
The sawtooth wave generation circuit 21 generates a sawtooth wave synchronized with the reference pulse generated by the oscillator 23, and the comparator 20 is turned off in a region where the output of the sawtooth wave generation circuit 21 has lowered the level of the reference power supply 22. Generate a pulse of.

Next, 24 is a switching transistor for forcibly setting the reference power source 22 to the L level and maintaining the output of the comparator 20 at the H level. The transistor 24 includes the counter 25, the flip-flop 26,
It is controlled by a NOR gate 27, an OR gate 28, an AE circuit 29, and a frequency divider 30. First, the counter 25 is stepped by a pulse obtained by dividing the reference pulse generated by the oscillator 23 by the frequency divider 30 after being cleared at the same time as the start of photographing. Therefore, the output of the counter 25 indicates the elapsed time after the start of the photographing operation. Further, since the output pulse of the frequency divider 30 is supplied to the drive circuit 10 and as a timing signal for stepping the drive pulse of the step motor 3, the output of the counter 25 is the rotational position of the step motor 3. That is, the rotational position of the drive ring 2 is also shown.

The output a of the counter 25 is applied to the set input of the flip-flop 26, the output b is applied to the reset input of the flip-flop 26, and the output Q of the flip-flop 26 is applied to one input of the NOR gate 27. or,
The c output of the counter 25 is added to the other input of the NOR gate 27.
After the counter 5 starts the counting operation, it becomes the L level during the period from the rise of the output a to the rise of the output b and after the rise of the output c. The output of the NOR gate 27 is applied to one input of the OR gate 28, and the high active exposure end signal generated by the AE circuit 29 is applied to the other input of the OR gate 28. Therefore, the output of the OR gate 28 is a of the counter 25.
AE circuit 2 during the period from the output rising to the b output rising and after the c output of the counter 25 rises
It becomes L level only during the period until 9 generates the exposure end signal, and becomes H level during the other period.

The transistor 24 is the OR gate 2
Since the output of 8 is conducted during the period of H level and the reference power source 22 is forcibly maintained at the L level, the comparator 20 synchronizes with the output of the sawtooth wave generation circuit 21 only while the output of the OR gate 28 is at the L level. The negative pulse thus generated is supplied to the AND gates 11, 13, 15, and 17.

Next, reference numeral 31 is an adjusting resistor for adjusting the product individual difference for each camera, 32 is a temperature detector for detecting the temperature at which the camera is currently placed, and attitude detection for detecting whether the camera is in the vertical position or in the horizontal position. These outputs are applied to the controller 34, and the controller 34 controls the generation level of the reference power source 22 in response to the outputs of these detectors to control the duty of the pulse generated by the comparator 22. To do. or,
Reference numeral 35 is a trigger switch for triggering the AE circuit 29.

Next, the operation of this embodiment will be described with reference to the above matters and the time chart of FIG. First, the adjusting resistor 31 is properly adjusted at the time of shipment, and the temperature detector 32 detects the temperature of the environment in which the camera is placed and the posture detector 33.
Adds the camera posture to the controller 34 as data,
The controller 34 controls the level of the reference power source 22 according to these outputs. In the case of the present embodiment, since the circuit is configured so that the duty of the pulse generated by the comparator 20 increases as the power supply level generated by the reference power supply 22 decreases, the temperature indicated by the temperature detector 32 is low, for example. The control is performed so that the level of the reference power source 22 decreases as the level decreases. Further, if the load on the mechanical member is large when the camera posture is in the vertical position, the level of the reference power source 22 is lowered when the posture detector 33 indicates the vertical position.

In the initial state, the mechanism is such that the cam follower 6b of the opening / closing lever 6 rides on the cam edge 2b of the drive ring 2 and the shutter blade 5 closes the aperture 1a. When the photographer presses the shutter button (or with the shutter button half stroke)
After setting the lens system (not shown) to the target in-focus position, the control device 22 gives a forward rotation command to the drive circuit 10, and
The clearing of the counter 25 is released. The oscillator 23 has been operating since the power was turned on, the sawtooth wave generation circuit 21 generates a sawtooth wave in synchronization with the reference pulse generated by the oscillator 23, and the frequency divider 30 generates the reference pulse generated by the oscillator 23. Is divided (the dividing ratio is appropriate), and the divided pulse is supplied to the drive circuit 10 and the counter 25.

First, the drive circuit 10 responds to the normal rotation command and outputs a pulse train for normal rotation (A) synchronized with the output of the frequency divider 30.
A pulse train in which the phase of the phase pulse leads the phase of the B-phase pulse by 90 degrees) is generated, and each pulse train is applied to AND gates 11, 13, 15, and 17, respectively. Also, the counter 2
5 is also stepped in synchronization with the output of the frequency divider 30.

Now, the counter 25 is stepped up and its a
Before the output goes high, the flip-flop 26 is reset and the output of the NOR gate 27 is high, so the output of the OR gate 28 is high. Therefore, the switching transistor 24 is turned on, and the level of the reference power supply 22 is forcibly set to the L level, so that the positive-phase input level of the comparator 20 always exceeds the negative-phase input level of the comparator 20, and the output of the comparator 20. Maintains H level. Therefore, AND gate 11,1
The outputs of 3, 15, and 17 are exactly the same as the output of the drive circuit 10. In other words, the coils 3a and 3 of the step motor 3 are
A drive current having a duty of 100% is supplied to b. When the A-phase (positive) pulse is at the H level, the transistors T1 and T2 are turned on and a positive drive current flows through the coil 3a. When the A-phase (negative) pulse is at the H level, the transistors T3 and T4 are turned on. A negative drive current for the coil 3a flows. Similarly, when the B-phase (positive) pulse is at the H level, the transistors T5 and T6 are turned on and a positive drive current flows through the coil 3b, and when the B-phase (negative) pulse is at the H level, the transistors T7 and T8 are turned on. The negative drive current of the coil 3b flows.

In response to the change in the drive current, the excitation state of the step motor 3 changes, the output pinion 3a rotates clockwise in FIG. 1, and the drive ring 2 and the guide ring 1b are rotated by the two-stage gear 4. Turn right around.

In this way, when the drive ring 2 is rotated rightward and the cam follower 6b of the drive opening / closing lever 6 falls from the cam edge 2b of the drive ring 2 to the cam edge 2c, the opening / closing lever 6 has the pin 6a and the shutter blade 5. Slot 5a formed in
The shutter blade 5 is rotated to the right by the biasing force of the spring 7 while being engaged. Further, the drive circuit 10 generates a drive pulse in synchronization with the output pulse of the frequency divider 30, and at the same time, the counter 25 is stepped in synchronization with the output pulse of the frequency divider 30. Then, when the cam follower 6b of the opening / closing lever 6 falls from the cam edge 2b to the cam edge 2c as the drive ring 2 rotates clockwise (for example, a total of four front and rear steps).
During the step), the output a and the output b of the counter 25 sequentially become H level. The Q output of the flip-flop 26 is at H level during the period from being set by the output of the counter 25 to being reset by the output of b, and the output of the NOR gate 27 is at L level during that period. On the other hand, since the AE circuit 29 does not generate the exposure end signal at this time, the output of the OR gate 28 becomes L level during the above four steps,
Meanwhile, the transistor 24 is cut off.

Therefore, the output level of the reference power supply 22 rises to the level controlled by the control device 34, and the comparator 20 compares the level of the reference power supply 22 with the sawtooth wave generated by the sawtooth wave generation circuit 21. A negative pulse is supplied to the AND gates 11, 13, 15, and 17. Therefore, the driving current intermittently pulsed is supplied to the coils 3a and 3b.

In the present embodiment, the reference power source 2 is output according to the outputs of the adjusting resistor 31, the temperature detector 32, and the attitude detector 34.
Since the output level of 2 is controlled, the drive current is controlled with the duty according to the power supply voltage fluctuation due to temperature, the individual difference of each product, and the camera attitude, and the aperture characteristic of the shutter blade 5 is stabilized. Is possible.

Now, as described above, the shutter blade 5 operates to open, the trigger switch 35 operates at a timing immediately before the pinhole is formed on the optical axis, and the AE circuit 29 starts integration of the field light. To do. Then, the AE circuit 29 sets the exposure end signal to the H level when the integrated value of the field light reaches a desired value. On the other hand, in order to reliably maintain the open state of the shutter blade 5 until the AE circuit 29 generates the exposure end signal,
The control device 34 applies a control signal to the drive circuit 10 to stop the updating of the A-phase and B-phase pulses, and continues to supply the drive current to the coils 3a and 3b. Therefore, if the exposure time is extended, the power consumption will increase.

However, when compared with the drive current required to rotate the step motor 3, the drive current required to stop the step motor 3 at a predetermined position can be small. In this embodiment, when the C output of the counter 25 goes high, the output of the NOR gate 27 goes low.
Then, the output of the OR gate 27 becomes L level and the transistor 24 is cut off. Therefore, the output level of the reference power supply 22 rises to the level controlled by the control device 34, and the comparator 20 outputs the reference power supply 22.
Is compared with the sawtooth wave generated by the sawtooth wave generation circuit 21, and a negative pulse is applied to the AND gates 11, 13, 15,
Supply to 17. Therefore, the driving current intermittently pulsed is supplied to the coils 3a and 3b, and the overall power consumption is reduced. The duty of the drive current at this time is also appropriately controlled in accordance with the output level of the reference power source 22, which is controlled according to the environment in which the camera is placed such as temperature and posture.

When the AE circuit 29 sets the exposure end signal to the H level, the control device 29 gives a normal rotation command to the drive circuit 10, and the drive circuit 10 restarts the stepping of the drive pulse.
Further, when the AE circuit 29 sets the exposure end signal to the H level,
Since the output of the OR gate 28 becomes H level and the transistor 24 becomes conductive, the AND gates 11, 13, 15,
The output of the comparator 20 added to 17 becomes H level. Therefore, the A-phase and B-phase drive pulses generated by the drive circuit 10 are transmitted with a duty of 100%, the step motor 3 resumes normal rotation with the maximum efficiency, and the drive ring 2 is guided by the guide ring 1b. Re-turn right along. And the cam follower 6b of the opening / closing lever 6
When riding on the cam edge 2e along the cam edge 2d, the opening / closing lever 6 rotates counterclockwise against the spring 7 and rotates the shutter blade 5 counterclockwise to close the aperture 1a.

Although the following operation is not directly related to the present invention, it is not shown in the time chart. However, when one exposure operation is completed in this way, the controller 34 gives a reverse rotation command to the drive circuit 10. The drive circuit 10 generates a reverse pulse in which the phase B is advanced, and rotates the step motor 3 counterclockwise. Therefore, the drive ring 2 is turned counterclockwise along the guide ring 1b to return to the initial position. In the returning process, the cam edges 2d and 2c pass the position of the cam follower 6b, but it is needless to say that the right and left rotation of the opening / closing lever 6 is prohibited by a member (not shown) during this reverse rotation.

In the above description, the example in which the switching transistor 24 is provided in the output stage of the reference power source 22 to control the duty is shown. For example, as shown in FIG. 4, the switching element 36 is provided in the power source line of the motor. It is possible to perform the same control even by providing. Also, in the above, an example in which a sawtooth wave is compared with a reference level to generate a pulse for duty control is shown, but if a signal other than the sawtooth wave has a slope and is periodically repeated, for example, A sine wave or a triangular wave may be used. Needless to say, other than the above, for example, a change in the power supply voltage may be directly detected as the detected signal.

[0033]

As described above, according to the present invention, the duty of the drive current can be controlled in the vicinity of the area where the shutter blades are actually operated to open, so that the individual difference of the camera and the change of the camera attitude can be suppressed. It is possible to stabilize the aperture characteristics without being affected by fluctuations in the power supply voltage due to consumption or a voltage drop during cold weather.
In addition, since it is possible to stabilize the rotation of the motor in the vicinity of the area where the shutter blades actually open, even if the rotation of the motor in other areas is accelerated, the rotation of the motor in the actual opening area is increased. There is less risk that the tracking of the mechanical members will become unstable, and the overall speed can be increased. Further, since it is possible to reduce the integrated value of the drive current at the time of long-time exposure, it is possible to reduce the power consumption of the power source.

[Brief description of drawings]

FIG. 1 is a plan view of a mechanism according to one embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a control circuit of the present invention.

FIG. 3 is a time chart of the above embodiment.

FIG. 4 is a circuit diagram showing a modified example of the circuit shown in FIG.

[Explanation of symbols]

 1 main plate 1a aperture 2 drive ring 2b, 2c, 2d, 2e cam edge 3 step motor 3a, 3b coil 5 shutter blade 6 opening / closing lever 6a cam follower 7 spring 11, 13, 15, 17 and gate 20 comparator 21 sawtooth wave generating circuit 22 Reference Power Supply 23 Oscillator 24 Transistor 25 Counter 26 Flip-Flop 27 NOR Gate 28 OR Gate 29 AE Circuit 30 Frequency Divider 31 Adjustment Resistor 32 Temperature Detector 33 Attitude Detector

Claims (2)

[Claims] 1. A blade member that opens and closes an exposure opening, a blade opening and closing member that is biased in a direction to open the blade member, a step motor that can rotate normally and reversely, and a gear connected to the step motor. A drive member having a portion for driving the blade opening / closing member in the blade opening direction and the blade closing direction, and the blade opening / closing member is operated by the operation of the driving member during the first rotation of the step motor. And a shutter drive device using a step motor as a drive source, which drives the blade opening / closing member in the blade closing direction by the operation of the driving member during the second rotation of the step motor after a predetermined time has elapsed. In the method described above, a means for intermittently supplying the motor drive current during the first rotation of the step motor is provided, and the duty of the motor drive current can be controlled. A shutter drive device using a step motor as a drive source. 2. A blade member that opens and closes the exposure opening, a blade opening and closing member that is biased in a direction to open the blade member, a step motor that can rotate in the forward and reverse directions, and a gear that is gear-connected to the step motor. A drive member having a portion for driving the blade opening / closing member in the blade opening direction and the blade closing direction, and the blade opening / closing member is operated by the operation of the driving member during the first rotation of the step motor. And a shutter drive device using a step motor as a drive source, which drives the blade opening / closing member in the blade closing direction by the operation of the driving member during the second rotation of the step motor after a predetermined time has elapsed. In the case where the time from the end of the first rotation of the step motor to the start of the second rotation exceeds a preset time, With means for supplying a flow intermittently,
A shutter drive device using a step motor as a drive source, wherein the duty of the motor drive current can be controlled.