JP3337541B2 - Camera positioning device driven by step motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a camera positioning apparatus using a stepping motor as a drive source which can be applied to a diaphragm blade positioning mechanism, a lens positioning mechanism, and the like.

[0002]

2. Description of the Related Art It is well known that a stepping motor is conventionally used as a driving source of a position member for a camera. FIG. 8 shows an example of a conventional drive pulse of the two-phase excitation method. The motor is driven by advancing the drive pulse train while maintaining a relationship such that the phase of the B-phase pulse advances by 90 degrees from the phase of the A-phase pulse. The motor rotates stepwise in the forward direction, and after driving to the target position, after stepping through the drive pulse train while maintaining the relationship that the phase of the A-phase pulse advances by 90 degrees from the phase of the B-phase pulse, the motor rotates in the reverse direction. Step rotation. FIG. 9 is an enlarged view of the vicinity of the switching of the pulse phase in FIG. 8. As shown in the enlarged view of FIG. 9, when the stepping motor advances, the stepping motor rotates stepwise with vibration due to overshoot. When the vibration converges, the rotor stationary angle with respect to the phase of the drive pulse has sufficient accuracy for practical use. Therefore, if the position member is connected to the motor and gear, sufficient positioning accuracy for practical use can be obtained. it can.

In a still camera, an aperture mechanism and a lens mechanism, which are examples of a position member, are necessarily driven prior to the operation of a shutter mechanism. In recent years, there has been proposed a mechanism which is also used as a driving source for the position member and the shutter mechanism, and drives the shutter mechanism after positioning the position member. As an example of such a dual-purpose drive mechanism, the drive member connected to the step motor is rotated forward by the forward rotation of the step motor, and the position member is rotated forward by the forward rotation of the drive member. It is known that a shutter mechanism is operated in a reverse rotation process of a driving member after a position member is locked at a target position by a stopping means.

[0004]

As described above, since the stationary angle of the stepping motor at the time of vibration convergence is sufficiently stable, when the position member is gear-connected to the motor,
Although practically sufficient positioning accuracy can be obtained even if some overshoot occurs, a locking mechanism such as a ratchet is required for a dual-purpose drive mechanism, and a locking mechanism such as a ratchet mechanism is used. In such a case, especially when the locking pitch is made fine to meet the demand for high resolution, the above-mentioned overshoot may cause the jump of the locking point, and the overshoot at the target locking point is minimized. There is a demand for reduction.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and uses a stepping motor as a driving source and locks a position member by locking means having a plurality of locking points. It is an object of the present invention to reduce overshoot of a step motor at a target locking point on the premise of a positioning device configured as described above. In summary, a positioning device for a camera using a stepping motor as a driving source according to the present invention includes: a stepping motor capable of rotating forward and reverse; a pulse control device for supplying a driving pulse train for stepwise rotating the stepping motor to the stepping motor; A driving member connected to the stepping motor and traveling in both forward and reverse directions corresponding to the rotation direction of the stepping motor; a position member traveling following the driving member in the process of traveling in the forward direction; Locking means having at least a plurality of locking points for locking the position member when the traveling direction of the driving member is reversed from the forward direction to the reverse direction, and by controlling the number of forward rotation pulses of the step motor, The pulse control device is based on the premise of a camera positioning device driven by a step motor configured to select a locking point of the locking means; After generating a forward pulse of n-th step corresponding to the engagement point of the object of Kigakaritome means, the first self-start frequency content of the step motor
Before the time elapses, a pulse having a phase corresponding to the pulse phase of the (n-1) th step is supplied to the stepping motor for a time shorter than one-half the self-starting frequency of the stepping motor. By generating the pulse again, the overshoot at the n-th step corresponding to the locking point is reduced.

[0006]

As is well known, a step motor rotates step by stepping a drive pulse. However, it is impossible to instantaneously rotate a step simultaneously with stepping of a drive pulse. Step rotation is performed after elapse of a delay time or a movement time determined depending on weight or the like. Therefore, the frequency of the drive pulse (self-starting frequency) that the step motor can follow is limited, and the step motor is driven by a pulse having a frequency lower than the self-starting frequency. As described above, according to the present invention, after the n-th forward rotation pulse corresponding to the target locking point is generated, the pulse of the (n-1) -th step is generated before the time equal to one-half the self-starting frequency has elapsed. A pulse having a phase corresponding to the phase is supplied to the step motor for a time shorter than a time equal to 1 / self-starting frequency. By generating the forward rotation pulse of the nth step, the step motor is n-1
It rotates from step to n steps.
Since a pulse having a phase corresponding to the pulse phase of the (n-1) th step is supplied before a time equal to one-seventh of the self-starting frequency has elapsed since the generation of the forward rotation pulse of the step, the stepping motor is driven until the nth step. Before the rotation is completed, an electromagnetic force in the reverse direction is generated between the rotor and the stator of the step motor, thereby suppressing overshoot at the nth step. If the pulse time in the reverse direction is longer than the time of one-half of the self-starting frequency, the step motor actually returns to the position of the (n-1) th step. Since this time is shorter than this time, this pulse in the reverse direction is used only for suppressing the overshoot.
When the pulse of the nth step is generated again, the actual step rotation angle becomes almost 0, and It converges to the nth step with almost no overshoot.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an example in which the present invention is applied to a mechanism using a single step motor as a drive source of a lens drive mechanism and a drive source of a shutter drive mechanism. In the figure, reference numeral 1 denotes a shutter base plate, and an exposure aperture 1a is formed in a central portion of the base plate 1. Reference numeral 2 denotes a step motor, and a pinion 3 is provided on a rotating shaft of the step motor 2, and the pinion 3 is formed via a two-stage gear 4 on a rack 5 a formed on a part of an outer edge of the drive ring 5.
And gear connected. The drive ring 5 is attached to the main plate 1 so as to be pivotable about the aperture 1a, and rotates in the same direction as the rotation direction of the pinion 3.

Reference numeral 6 denotes a lens driving ring which is an example of a position member which is attached to the main plate 1 so as to be pivotable about the aperture 1a. The lens driving ring 6 is provided with a right turning property by a spring 7. An inclined cam 6a for extending an unillustrated lens group in the optical axis direction is formed on the front side surface of the lens driving ring 6, and the unillustrated lens group is extended when the lens driving ring 6 rotates left.
The driving force for rotating the lens driving ring 6 counterclockwise depends on the step motor 2, and this driving force is
Is transmitted via That is, the engagement pin 6b implanted on the back surface of the lens drive ring 6 is provided on the left-handed path of the engagement protrusion 5b formed on the drive ring 5, and the drive ring 5 is rotated leftward from the illustrated initial state. In the process of engaging
b is engaged with the engagement projection 5b, the lens drive ring 6
Rotates counterclockwise following the drive ring 5.

A lens driving ring 6 is provided on the shaft 1b on the main plate 1.
A ratchet lever 8 for locking the lever is swingably supported, and the ratchet lever 8 is provided with a left-turning property by a spring 9. However, in an initial state, the ratchet lever 8 comes into contact with a curved portion 5c formed on the drive ring 5. The left turn is regulated. On the other hand, a ratchet lever 8 is provided on the outer edge of the lens drive ring 6.
A ratchet gear 6c is provided in a row, and the lens driving ring 6 is driven by the driving ring 5 to make a left-handed rotation.
When the lens rotates clockwise, the lens drive ring 6
Any one of the claws c is locked by the ratchet lever 8 to prevent the spring 7 from returning due to the urging force. And
When the bent portion 5c of the drive ring 5 flips up the ratchet lever 8 in the process of turning the drive ring 5 clockwise toward the initial position, the engagement of the ratchet gear 6c by the ratchet lever 8 is released, and the lens drive ring 6 is released. Turns clockwise toward the initial position by the urging force of the spring 7.

A shaft 1c on the main plate 1 has a blade drive lever 10
Are swingably supported, and the blade drive lever 10 is provided with a right-turning property by a spring 11. However, in the initial state shown in the drawing, a cam follower 10a formed on the blade drive lever 10 has a protrusion formed on the drive ring 5. The right-handed rotation is restricted by contacting the piece 5d and the protruding piece 6d formed on the lens drive ring 6. A V-shaped cam 5e is formed on the drive ring 5, and the cam follower 10a rotates the drive ring 5 clockwise after the drive ring 5 and the lens drive ring 6 turn left once from the initial state shown in the figure. 5e, the blade drive lever 10 turns clockwise and the drive ring 6
When the cam follower 10a further turns clockwise and rides on the protruding piece 5d from the V-shaped cam 5e, the blade drive lever 10 turns left and returns to the initial position. The blade drive lever 10 is engaged with a shutter blade 12 swingably supported on a shaft 1d on the back surface of the main plate 1. When the blade drive lever 10 turns clockwise, the shutter blade 12 opens the aperture 1a and drives the blade. When the lever 10 rotates counterclockwise, the shutter blade 12 moves to the aperture 1.
Close a.

Next, FIG. 2 is a block diagram showing a control system of the present invention, and 2a and 2b show coils constituting the step motor 2. A drive current is supplied to the coils 2a and 2b from a transistor bridge circuit, and the drive current is controlled by an A-phase pulse and a B-phase pulse generated by the control circuit 20. More specifically, the A-phase pulse is applied to the base inputs of the transistors T1 and T4 and to the base inputs of the transistors T2 and T3 via the inverter 21. Therefore, the A-phase pulse is L
When the level is at the level, the transistors T1 and T2 are turned on, and the drive current flows through the coil 2a from left to right in the drawing. The drive current flows to the left. Similarly, the B-phase pulse is applied to transistors T5 and T5.
8 and the inverter 22
To the base inputs of the transistors T6 and T7. Therefore, when the B-phase pulse is at the L level, the transistors T5 and T6 conduct, and the drive current flows through the coil 2b from left to right in the drawing. When the B-phase pulse is at the H level, the transistors T7 and T8 conduct and the coil The drive current flows through the 2b from right to left in the drawing.

Reference numeral 23 denotes a known distance measuring device for measuring the distance to the object. Distance information to the object measured by the distance measuring device is input to a control circuit 20, and the control circuit 20 responds to the distance information. The number of rotation steps of the step motor 2 is controlled. 24 is a counter which can be up / down.
The control circuit 20 counts up the counter 24 each time a forward rotation pulse is supplied to the step motor 2, and counts down the counter 24 each time a reverse rotation pulse is supplied to the step motor 2. Reference numeral 25 denotes a setting device for setting a numerical value "2" smaller than the step rotation speed of the step motor 2 necessary for performing a focusing operation at a position corresponding to the target distance information. The numerical value and the set value of the setting device 25 are compared by a comparison circuit 26, and the comparison circuit 26 generates a coincidence signal when the count value of the counter 24 reaches the set value of the setting device 25.

Next, the flowchart of FIG. 3 and FIGS.
The operation of the above embodiment will be described with reference to the time chart of FIG. Note that the time of (1 / self-start frequency) of the step motor is a value that fluctuates depending on the motor torque and load. In the following operation example, when the step motor 2 rotates forward (one-self-start frequency). Is, for example, 3 ms,
The description will be made assuming that the time of (1 / self-starting frequency) during the reverse rotation of the step motor 2 is, for example, 2 ms. First, in an initial state, the mechanism members are in a state shown in FIG. 1, and a sequence is started by pressing a shutter button (not shown) in this state. First, after resetting the counter 24, the control circuit 20 activates the distance measuring device 23 to measure the distance to the subject. The subject distance information obtained from the distance measuring device 23 is input to the control circuit 20, and a value obtained by subtracting “2” from the step rotation speed of the step motor 2 necessary for performing the focusing operation on the subject distance information is set by the setting unit 25. Is set to Further, the control circuit 20 has an initial phase for the step motor 2 [H. H] pulse of 10 m
supply. By supplying the pulse of the initial phase, the transistors T1, T2 and T5, T6 of the stepping motor 2 are turned on, and the driving current flows through the coils 2a, 2b from left to right in FIG. And stabilized.

Thereafter, the control circuit 20 supplies the stepping motor 2 with a pulse whose phase of the B phase is advanced by 90 degrees at a period of 4 ms longer than the time of (1 / self-starting frequency), and increments the forward rotation pulse. The counter 24 is counted up every time. The phase of the B phase is 90 for the step motor 2.
By supplying a pulse that is advanced one step, the pinion 3 of the stepping motor 2 rotates forward (left-handed rotation in FIG. 1), and the drive ring 5 rotates left-handed via the two-stage gear 4. The lens drive ring 6 is driven by the drive ring 5 from the time when the engagement protrusion 5b formed on the drive ring 5 engages the engagement pin 6b on the back surface of the lens drive ring 6 with the left rotation of the drive ring 5. While turning to the left, the tilt cam 6a extends an imaging lens (not shown) in the optical axis direction.

The control circuit 20 monitors the output of the comparison circuit 26 every time a pulse for forward rotation is supplied to the step motor 2, and controls the step motor 2 forward to two steps before the target step position. Counter 2 when turned
4 matches the set value of the setting device 25,
6 generates a coincidence signal.

When the control circuit 20 receives the coincidence signal from the comparison circuit 26, the control circuit 20 supplies a further forward rotation pulse to the step motor 2 for one step and counts up the counter 24. The subsequent operation differs depending on whether the target number of steps is odd or even.
First, the case of an even number will be described. If the target number of steps is an even number, the control circuit 20 sets one of the target step positions to one.
The phase state before the step is maintained for 20 ms. This 20
During the waiting time of ms, the overshoot of the step motor converges, and the step motor 2 and the members connected to the step motor 2 converge to the rotor stationary angle of the step motor 2.

After the member is stabilized in the step one step before the target step position in this way, the control circuit 20 supplies a pulse for normal rotation for 1.5 ms, and subsequently supplies a pulse for reverse rotation for 1.4 ms. After the supply, a pulse for normal rotation is further supplied for 15 ms. By supplying the first 1.5 ms forward rotation pulse, the pinion 3 of the step motor 2 is turned on.
Generates a driving force in the left-handed direction, but the time of 1.5 ms is sufficiently shorter than the time of (1 / self-starting frequency), so that the step motor 2 approaches the target step position in this time. , It does not reach the target step position. Then, a driving force in the reverse rotation direction is generated in the stepping motor 2 by the next reverse rotation pulse of 1.4 ms.
The time of 4 ms is sufficiently shorter than the time of (1 / self-starting frequency), and the inertia force in the forward rotation is acting on the step motor 2. Does not return to the step one step before the target step position, but generates only the reverse rotation torque enough to stop the rotation by the 1.5 ms forward rotation pulse immediately before. Therefore, when a forward rotation pulse of 15 ms is continuously applied, the step motor rotates forward from the very close position of the target step position toward the target step position, and almost no overshoot occurs at the target step position.

After maintaining the pulse phase state at the target step position for 15 ms, the control device 20 sends a reverse rotation pulse in which the phase of the A-phase pulse is advanced by 90 degrees with respect to the phase of the B-phase pulse to the step motor 2 at a period of 2.5 ms. Then, the step motor 2 is turned clockwise. If the target step position is an odd-numbered step, the normal rotation pulse time immediately before the target step position is set to 4 ms, and then, for example, 25 steps in the target step.
A pulse of ms is supplied, and the operation shifts to the same inversion operation as described above. The reason why the pulse control immediately before the target position is changed depending on whether the target step position is an even number or an odd number as described above is that the step motor has a structure in which the motor torque is reduced every rotation step of the motor. This is because the overshooting at the step where the torque is relatively large and the torque is relatively large becomes relatively large. In both cases, a short-time reverse rotation pulse may be supplied in the same manner as described above.

When the step motor 2 rotates clockwise, the drive ring 5 also rotates clockwise via the two-stage gear 4, but the lens drive ring 5 is moved to a position where the ratchet gear 6c is locked by the ratchet lever 8 and is extended. Stay in. When the trapezoidal cam 5e passes through the cam follower 10a in the process of turning the drive ring 5 clockwise, the opening / closing lever 10 is
Since the cam follower 10a falls onto the trapezoidal cam 5e, the spring 11 turns clockwise to open the shutter blade 12. Thereafter, when the drive ring 5 further turns clockwise, the opening / closing lever 10 turns counterclockwise against the spring 11 to close the shutter blade 12 because the cam follower 10a rides on the protruding piece 5d from the trapezoidal cam 5e.

The controller 20 counts down the counter 24 every time a reverse rotation pulse is supplied to the step motor 2 during the reverse rotation of the step motor 2, and when the count value of the counter 24 is reduced to "0", the drive ring 5 is initialized. Reach the position. Immediately before the drive ring 5 reaches the initial position, the bent portion 5c of the drive ring 5
Is rotated clockwise against the spring 9, the latching of the ratchet gear 6c by the ratchet lever 8 is released, and the lens drive ring 6 is returned clockwise to the initial position by the urging force of the spring 7 to perform one shooting operation. To end.

FIGS. 6 and 7 show an embodiment in which the pulse time is not extended in the step one step before the target step position. In this case, the step motor 2 is not used. Since the step rotation is performed toward the target step without converging to the stable step position one step before this step, slight overshoot occurs, but the amount of overshoot can be reduced.
In the above description, an example in which a lens driving mechanism is used as an example of the positioning device is shown. However, the present invention is applicable to a diaphragm driving mechanism and other positioning devices as long as the positioning device is locked by a locking mechanism such as a ratchet. It is needless to say that can be applied. Also, in the above description, an example was shown in which a two-phase excitation method was adopted as the excitation method for the step motor.
It goes without saying that a two-phase excitation system may be used.

[0022]

As described above, according to the present invention, the overshoot of the step motor at the target step position can be greatly reduced, so that the step motor is used as a drive source and the position member is moved at the target position. In a positioning device that is locked by the locking means, even if the resolution of the locking means is increased, the risk of jumping over the target locking point due to the effect of overshoot can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a plan view of a shutter driving mechanism that also serves as a lens driving mechanism in which the present invention is applied to a lens driving mechanism as an example of a positioning device.

FIG. 2 is a block diagram showing an example of a control system according to the present invention.

FIG. 3 is a flowchart showing an operation example of the present invention.

FIG. 4 is a time chart showing an operation example of the present invention.

FIG. 5 is a partially enlarged view of the time chart shown in FIG. 4;

FIG. 6 is a flowchart showing another operation example of the present invention.

FIG. 7 is a partially enlarged view of the time chart shown in FIG. 6;

FIG. 8 is a time chart showing a conventional control operation example.

FIG. 9 is a partially enlarged view of the time chart shown in FIG. 8;

[Explanation of symbols]

 2 Step motor 20 Control circuit 5 Drive ring 6 Lens drive ring 6c Ratchet gear 8 Ratchet lever 24 Counter 25 Setting device 26 Comparison circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G02B ⁷ /02-7/16 G03B 9/00-9/70 G03B 13/36

Claims (2)

(57) [Claims] 1. A step motor capable of forward and reverse rotation, a pulse control device for supplying a drive pulse train for stepwise rotating the step motor to the step motor, and a pulse control device connected to the step motor and corresponding to a rotation direction of the step motor. A driving member that travels in both forward and reverse directions, a position member that travels following the driving member while the driving member travels in the forward direction, and that the traveling direction of the driving member reverses from the forward direction to the reverse direction. Locking means having at least a plurality of locking points for locking the position member, wherein the locking point of the locking means is selected by controlling the number of forward rotation pulses of the step motor. In a camera positioning device using a stepping motor as a drive source, the pulse control device generates a forward rotation pulse of an nth step corresponding to a target locking point of the locking means. After the occurrence, the pulse having a phase corresponding to the pulse phase of the (n-1) -th step is set to be shorter than the time equal to one-half the self-starting frequency of the step motor before the time equal to the self-starting frequency of the step motor elapses. A positioning device for a camera using a step motor as a drive source, wherein the pulse of the n-th step is generated again after supplying the pulse to the step motor for a short time. 2. A positioning device for a camera using a stepping motor as a driving source according to claim 1, wherein said pulse control device is configured to generate a forward rotation pulse of an nth step corresponding to a target locking point of said locking means. A positioning device for a camera using a stepping motor as a drive source, characterized in that the immediately preceding pulse time is a time sufficient for the operation of the drive system to converge.