JPH07337096A - Positioning unit employing stepping motor as drive source - Google Patents

Abstract

PURPOSE:To obtain a positioning unit comprising an engaging mechanism, e.g. a ratchet mechanism, and employing a stepping motor as a drive source in which the positioning accuracy is enhanced by suppressing the overshoot. CONSTITUTION:A rotor 1a rotates forward to turn a ring 15 leftward thus turning a ring 17 leftward. When the rotor 1a rotates reversely to turn the ring 15 rightward, a click in a ratchet click 17c corresponding to the N-th step is engaged with a ratchet lever 19 to position the ring 17. When the overshoot increases at N-th step, the click may skip to (N-1) th step. During transition from (N-1) th step to N-th step, the exciting states at (N-1)th step and N-th step are repeated alternately to increase the duty ratio at N-th step. Consequently, the traveling speed is decreased and the overshoot is suppressed at N-th step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning device using a step motor as a drive source, and more particularly to a step motor capable of rotating in the forward and reverse directions and a step motor connected to the step motor in both the forward and reverse directions corresponding to the rotation direction of the step motor. A driving member to be driven, a position member driven by the driving member when the driving member is driven in the forward direction, and a position member driven when the traveling direction of the driving member is switched from the forward direction to the reverse direction. Driving a step motor capable of reducing overshoot when the traveling direction of the driving member is changed, on the premise of a positioning device including a locking member that locks the position member at any one of N locking points. The present invention relates to improvement of a positioning device as a source.

[0002]

2. Description of the Related Art FIG. 8 is a plan view showing a configuration example of a four-pole step motor used in the present invention and the prior art on which the present invention is based. 1a is a rotor in which north poles and south poles are alternately arranged at intervals of 90 degrees around a rotating shaft 1b, and 1c and 1d.
Is a stator, and 1e and 1f are coils, respectively.
By switching the energizing direction for e, the stator 1
The polarity of the magnetic poles 1g and 1h of c changes, and the coil 1f
1d by switching the energizing direction to
The polarities of the magnetic poles 1i and 1j included in the change. In the example shown in FIG. 8, the magnetic pole 1g is converted into the arc angle of the rotor 1a.
The angle between -1h and the angle between the magnetic poles 1i-1j is 90.
And the angle between the magnetic poles 1g-1i is 45 degrees.

Next, FIG. 9 shows an example of a motor driver MD for switching the drive current supplied to the coils 1e and 1f. T1 to T8 each represent a transistor, and 2 a pulse train P1 for driving. 3 shows a control device for generating P4. The pulses P1 and P2 and the pulses P3 and P
No. 4 has the polarity reversed. Also, the pulses P1 and P3
The phases of the pulses P2 and P4 are shifted by 90 degrees depending on the rotation direction of the motor. The pulse P1 is applied to the base of the transistor T1 via the inverter I1 and directly to the base of the transistor T2.
2 is added via inverter I2 to the base of transistor T3 and directly to the base of transistor T4. Therefore, when the pulse P1 goes high and the pulse P2 goes low, the transistors T1 and T2 turn on and the transistors T3 and T4 turn off.
e-Transistor T2-A current flows through the resistor R1. Conversely, when the pulse P1 goes to the L level and the pulse P2 goes to the H level, the transistors T1 and T2 turn off and the transistors T3 and T4 turn on. Includes a transistor T3-coil 1e-transistor T4-
A current will flow through the resistor R1 and the pulse P1
By controlling P2, the direction of the current flowing through the coil 1e can be controlled. Similarly, the pulse P3 is applied to the base of the transistor T5 via the inverter I3 and directly to the base of the transistor T6, and the pulse P4 is applied to the base of the transistor T7 via the inverter I4 and the transistor T7.
It has been added directly to the base of 8. Therefore, pulse P3
Is high and the pulse P4 is low, the transistors T5 and T6 turn on and the transistors T7 and T
Since 8 is turned off, a current flows between the power supply and the ground through the transistor T5-coil 1f-transistor T6-resistor R2, and conversely, the pulse P3 is at the L level and the pulse P4 is at the L level.
When the H level becomes H level, the transistors T5 and T6 are turned off and the transistors T7 and T8 are turned on. Therefore, a current flows between the power source and the ground through the transistor T7-coil 1f-transistor T8-resistor R2, and the pulse P3・ Coil 1f by controlling P4
It is possible to control the direction of the electric current flowing through. The diode in the circuit diagram is for backflow prevention.

Since the magnetized states of the magnetic poles 1g, 1h, 1i, 1j change corresponding to the directions of the currents flowing through the coils 1e, 1f, the pulse P3 generated by the control unit 2 is generated as shown in FIG. The direction of rotation of the rotor 1a is reversed depending on whether the phase of P4 is advanced 90 degrees from the phase of pulses P1 and P2 or when the phase of pulses P3 and P4 is advanced 90 degrees from the phase of pulses P1 and P2. Therefore, it is possible to control the motor rotation direction by controlling the phase order of the drive pulses.

In the case of an apparatus using a step motor as a drive source, it is possible to perform positioning by fixing the energized state of the motor at a predetermined position, but there is a limit to the mounting space such as a camera. In the case of a certain device, there is a demand to use one motor as a driving source for two or more members (for example, a lens driving mechanism and a shutter driving mechanism). In such a case, the target member is, for example, a ratchet or the like. A method of using the step motor as a drive source for other members after locking with the locking member is generally adopted.

[0006] Fig. 11 shows a preferred example thereof, 3 is a pinion directly or indirectly connected to a rotor, 4 is a rack 4a part of which meshes with the pinion 3 and left and right by pins 5 and 6. When the pinion 3 rotates clockwise, the rotation is transmitted to the drive member 4 via the rack 4a, and the drive member travels to the left in the drawing. Further, 7 is a position member movably supported to the left and right by pins 8 and 9, and the position member 9 is urged to the right by a spring 9 (the spring indicates only an urging direction by an arrow). ing. The position member 7 is provided with an engagement pin 7a. Since the engagement pin 7a is located on the leftward traveling path of the engagement protrusion 4b formed on the drive member 4, the drive member is not driven. When 4 moves to the left, the position member 7 moves to the left against the biasing force of the spring 10 while the engagement pin 7a is engaged with the engagement projection 4b.

Next, 11 is a ratchet lever for locking a plurality of ratchet clicks 7b formed on the position member 7. The ratchet lever 7 is given a left-handed turning force by a spring 12, but in the initial state shown in the figure. The ratchet return lever 4c formed on the drive member 4 restricts left-handed rotation.

Now, with the state shown in FIG. 11 as the initial state, when a pulse train in which the phase of the pulse P3 shown in the left half of FIG. 10 leads the phase of the pulse P1 by 90 degrees is added to the step motor to rotate the pinion 3 clockwise. The drive member 4 travels to the left in the drawing while the rack 4a is meshed with the pinion 3, and at this time, the engaging projection 4b engages the engaging pin 7a, so that the position member 7
Also runs to the left against spring 10. After that, FIG.
When a pulse train in which the phase of the pulse P3 is delayed by 90 degrees from the phase of the pulse P1 as shown in the right half of FIG. Drive to the right above,
At this point, the ratchet lever 11 is released from the ratchet return lever 4c, so the ratchet lever 1
1 locks the ratchet click 7b, so that only the drive member 4 travels to the right. Immediately before the drive member 4 returns to the initial position, the ratchet return lever 4c rotates the ratchet lever 11 clockwise, so that the position member 7 is released from the ratchet lever 11 and returned to the initial position by the spring 10. Therefore, according to this type of mechanism, it becomes possible to drive a member (not shown) by the drive member 4 during the period from when the pinion 3 is reversed until the position member 7 is released from the ratchet lever 11.

[0009]

By the way, in the case of the positioning device in which the step motor and the ratchet mechanism are combined as described above, the positioning is performed by the step rotation speed until the step motor is reversed. The ratchet lever 11 surely moves over the claw corresponding to the Nth step so that the claw corresponding to the Nth step (N is an arbitrary integer for the purpose of locking) can be reliably locked. The lever 11 and the ratchet click 7b are aligned. In addition, it is naturally impossible for the step motor to rotate while being completely stationary at each step, and the step motor rotates stepwise with vibration due to overshoot. The amount of this overshoot is determined by the torque of the motor and the inertial force of the load, etc. If this amount of overshoot always reaches the value assumed at the time of design, stable positioning accuracy can be obtained. In the case of dependent devices, the overshoot amount is not always stable because the motor torque fluctuates due to fluctuations in the power supply voltage due to power consumption and temperature changes, and load fluctuations occur due to the shooting posture. Therefore, there is a plan to lock with the nail corresponding to the Nth step N +
There is a problem that the locking point accuracy is not always stable, such as locking the claw corresponding to the first step.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of these problems, and obtains stable locking point accuracy by suppressing the amount of overshoot near the locking point as much as possible. It is an object of the present invention to provide a positioning device using a step motor as a drive source. In summary, the positioning device using the step motor of the present invention as a driving source is:
A driving member that is connected to the step motor and travels in both forward and reverse directions corresponding to the rotation direction of the step motor; a position member that is driven by the driving member when the driving member travels in the forward direction; A motor that sequentially updates the excitation state of the step motor, rotates the step motor in the forward direction up to the target Nth step, and then reverses the update direction of the excitation state of the step motor to rotate the step motor in the reverse direction. Assuming a positioning device including a control means and a locking member that locks the position member at a locking point corresponding to the Nth step when the traveling direction of the driving member is switched from the forward direction to the reverse direction: When the step motor is rotated from the (N-1) th step to the Nth step, the motor control means sets the excitation state and the Nth step corresponding to the (N-1) th step. Finally the duty ratio of the excitation states corresponding to N-th step with repeated a plurality of times an excitation state corresponding to up eyes alternately is characterized in that the manner is increased to 100 percent.

[0011]

That is, according to the present invention, since the rotational speed during the movement from the step immediately before the target step to the target step is greatly reduced, the inertial force when the target step is reached is reduced, Since the absolute amount of overshoot in the step is extremely small, the absolute amount of error is extremely small even if the ratio of overshoot error is constant, and stable locking point accuracy can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. Even in the embodiments described below, the structure of the step motor itself and the structure of the motor driver MD are shown in FIG.
Or the conventional one shown in FIG. FIG. 1 shows an embodiment in which the present invention is applied to a positioning device for a lens drive mechanism, in which a single step motor is used as a drive source for a lens drive mechanism and a shutter drive mechanism. The pinion 3 meshes with the gear 13 that forms the two-stage gear, and when the pinion 3 rotates, the gear 13 and the gear 14 that form the two-stage gear rotate integrally.
Reference numeral 15 denotes a drive ring that is supported so as to be rotatable about the exposure aperture 16, and the rack 15a formed on a part of the outer edge of the drive ring 15 meshes with the gear 14, and the rotation of the gear 14 causes the rotation of the drive ring 15. Be transmitted to.

A lens drive ring 17 is supported in front of the drive ring 15 so as to be rotatable about the exposure aperture 16 as well, and the lens drive ring 17 receives a right turning force by a spring 18. In the initial state, further clockwise rotation is restricted by a stopper member (not shown). Further, an engagement pin 17a is planted on the back surface of the lens drive ring 17, and the engagement pin 17a is formed on the outer edge of the drive ring 15 so as to project therefrom.
It is located on the left-handed path of 5b. Therefore, Pinion 3
When the engagement pin 17a is engaged with the engagement projection 15b in the process in which the rotation of the drive ring 15 is transmitted to the left and the drive ring 15 rotates counterclockwise, the lens drive ring 17 resists the right rotation force received from the spring 18. Follow to turn left.

On the front side surface of the lens drive ring 17, three cam followers 17b are formed at 120 degree intervals. The cam followers 17b are also formed on the film side surface of the lens barrel (not shown) at 120 degree intervals. Supports the tilt cam. Therefore, when the lens drive ring 17 is turned counterclockwise from the illustrated state, the three cam followers 17b push up the inclined cams formed on the lens barrel (not shown), so that the lens barrel (not shown) is extended toward the subject. Therefore, the focus adjustment (or zooming may be performed) can be performed by appropriately controlling the left-handed rotation amount of the lens drive ring 17. A ratchet click 17c for locking the lens drive ring 17 in a left-handed state is formed on a part of the outer edge of the lens drive ring 17, and 1
Reference numeral 9 is a ratchet lever for locking the ratchet click 17c. The ratchet lever 19 is rotatably supported by a shaft 20 and is given a left-handed turning force by a spring 21.
The counterclockwise rotation is restricted by the engagement protrusion 15b formed on the No. 5 side.

Reference numeral 22 denotes a blade opening / closing lever for opening / closing driving a shutter blade (not shown) for opening / closing the exposure aperture 16, and the blade opening / closing lever 22 is swingably supported by a shaft 23. A pin 22a is planted on the back surface of the blade opening / closing lever 22, and the pin 22a is engaged with a shutter blade (not shown). Shutter blades are associated to open the exposing aperture 16. The blade opening / closing lever 22 is given a right-handed turning force by a spring 24, but in the initial state, a cam follower 22b provided on the blade opening / closing lever 22 abuts on a restricting projection 17d formed on the lens drive ring 17. The blade opening / closing lever 22 is controlled to rotate rightward from the initial state shown in FIG. 1, and then the blade opening / closing lever 22 rotates rightward and then rightward.
It operates by 15d and 15e.

FIG. 2 is a block diagram of the control system.
If 1f is a coil of a step motor similar to that shown in the conventional example, MD is also a motor driver configured similarly to that shown in FIG. 9, 25 is a main power switch of the camera, 26 is a release switch, 27 is a known photometric circuit, Reference numeral 28 is a known distance measuring circuit, 29 is a known trigger circuit for generating a trigger signal for exposure control when a shutter blade (not shown) reaches a pinhole state, and 30 is a control device constituted by a microcomputer. . Next, the above items FIG. 3 and FIG.
The operation of this embodiment will be described with reference to the time chart of FIG. 6, the flowchart of FIG. 6, and the plan views showing changes in the mechanical members of FIGS.

First, in the initial state, the mechanical members are as shown in FIG.
When the release switch 26 is turned on after the main switch 25 has been made, the control sequence starts. The control device 30 is a distance measuring circuit 28.
Also, the distance information and the luminance information are read from the photometric circuit 27, respectively, and the number N of normal rotation steps of the step motor is set corresponding to the distance information. The controller 30 supplies the motor driver MD with the forward rotation pulse in which the phases of the pulses P3 and P4 are advanced by 90 degrees relative to the phases of the pulses P1 and P2, and causes the pinion 3 to rotate counterclockwise in steps. The step rotation of the pinion 3 is transmitted to the drive ring 15 via the gear 13-gear 14-rack 15a, and the drive ring 15 also rotates counterclockwise about the aperture 16. It should be noted that the cams 15e and 15d are moved by the cam follower 22b while the drive ring 15 is rotating counterclockwise.
, But the cam follower 22b has a protruding piece 17d.
Since the blade opening / closing lever 22 is in contact with the blade, the blade opening / closing lever 22 does not rotate to the right.

From the time when the engaging projection 15b engages the engaging pin 17a in the process of the drive ring 15 turning counterclockwise, the lens drive ring 17 follows the drive ring 15 and turns counterclockwise.
A lens barrel (not shown) is extended corresponding to the left-handed rotation amount of the lens drive ring 17. By the way, in the process of rotating the pinion 3 counterclockwise from the initial state shown in FIG. 1, when the target focus position is the Nth step, as shown in FIG. 3, the lens when rotating from the (N-1) th step to the Nth step Drive ring 17
It is the essence of the present embodiment that the inertial force of the lens drive ring 17 is reduced by decreasing the rotation speed of the lens drive ring and the absolute amount of the overshoot of the lens drive ring 17 at the Nth step is reduced. .

In the example shown in FIG. 3, pulse (P1, P3)
Is (H, L) in the (N-1) th step, and N
It is (L, L) at the step. In this embodiment, as shown in an enlarged view in FIG. 5, when rotating from the (N-1) th step to the Nth step, the combinations of the pulses (P1, P3) are (H, L) and (L, L). ) Are alternately repeated a plurality of times, during which the duty ratio of (H, L) corresponding to the (N-1) th step is gradually decreased, and the duty ratio of (L, L) corresponding to the Nth step is finally determined. Is 10
It is gradually increasing to 0%. Therefore, in this duty control section, the forward rotation torque and the reverse rotation torque are alternately generated, and the duty ratio at which the forward rotation torque is generated gradually increases, while the duty ratio at which the reverse rotation torque is generated is gradually increased. Gradually decreases,
As shown in FIG. 3, in this duty control section, the rotation speed of the motor decreases and the inertial force of the drive ring 15 and the lens drive ring 17 decreases. Therefore, the absolute amount of overshoot of the lens drive ring 17 at the Nth step is reduced, and the risk of the lens drive ring 1 jumping to the (N-1) th step due to the influence of the overshoot is reduced.

Then, the control device 30 rotates the step motor to the target N-th step and then outputs the pulse P1.
A reverse rotation pulse in which the phases of the pulses P3 and P4 are delayed by 90 degrees from the phase of P2 is supplied to the motor driver MD to rotate the pinion 3 clockwise, and the drive ring 15 also rotates clockwise accordingly. When the drive ring 15 rotates clockwise, the lens drive ring 17
Also makes a slight right turn due to the biasing force of the spring 18,
The pawl corresponding to the Nth step of the ratchet click 17c formed on the lens drive ring 17 is locked to the ratchet lever 19, and only the drive ring 15 is rotated right. In addition, Fig. 6 shows ratchet click 17 in this way.
It shows a state in which c is locked by the ratchet lever 19, and at this time, the cam follower 22b of the blade opening / closing lever 22 rides on the cam edge 15c.

From the state shown in FIG. 6, the drive ring 15
When only the blade turns to the right, the cam follower 22b of the blade opening / closing lever 22 falls from the cam edge 15c to the cam edge 15d.
The blade opening / closing lever 22 is rotated clockwise by the spring 24 as shown in FIG. Therefore, the pin 22a implanted on the back surface of the blade opening / closing lever 22 operates the shutter blade (not shown) in the opening direction, and the trigger circuit 29 generates a trigger signal immediately before the shutter blade forms a pinhole. Control device 30
When this trigger signal is accepted, the reverse rotation pulse is held until the time corresponding to the brightness information input from the photometry circuit 27 has elapsed, and when the time corresponding to the exposure second has elapsed, the reverse rotation pulse is restarted and the drive ring 15 Rotate further to the right. Therefore, the cam follower 22 of the blade opening / closing lever 22
Since b rides on the cam edge 15e, the blade opening / closing lever 2
2 rotates counterclockwise against the spring 24 to close and drive the shutter blade (not shown). Then, the step motor is rotated in the reverse direction to the initial state shown in FIG. 1 to complete one photographing operation.
In the process in which the drive ring 15 is rotated rightward to the initial position shown in FIG. 1, the engagement protrusion 15b formed on the drive ring 15 flips up the ratchet lever 19 to cause the lens drive ring 1 to move.
Since 7 is released from the ratchet lever 19, the lens drive ring 17 is rotated clockwise by the spring 19 and returns to the initial position.

In the above description, the case where the photographing lens is positioned is described as an example of the position member. However, the present invention can be applied to, for example, the positioning of the diaphragm, and of course, it can be used for purposes other than the camera. It goes without saying that the present application can be applied. Further, although the example in which the duty ratio in the duty control section is changed in 10 steps has been shown above, it goes without saying that the number of control steps is not limited to this.

[0023]

As described above, according to the present invention, the speed of the position member when rotating from the step immediately before the target step position to the target step position is greatly reduced, so that at the target step position. The absolute amount of overshoot of the position member becomes extremely small, and when the error rate of overshoot is constant, the absolute amount of overshoot error becomes small. The risk of point accuracy degradation is reduced.

[Brief description of drawings]

FIG. 1 is a plan view of a shutter drive mechanism that also serves as a lens drive mechanism according to an exemplary embodiment of the present invention, as viewed from a subject side.

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

FIG. 3 is a time chart showing an example of a control operation of the present invention.

FIG. 4 is a flowchart showing an example of a control operation of the present invention.

5 is an enlarged view of a main part of the time chart shown in FIG.

6 is a plan view showing a state where the lens driving ring is locked by the mechanism shown in FIG.

FIG. 7 is a plan view showing a state where the blade opening / closing lever is operated to open by the mechanism shown in FIG.

FIG. 8 is a principle diagram of a step motor.

FIG. 9 is a circuit diagram showing a circuit example of a motor driver.

FIG. 10 is a time chart showing an example of a conventional two-phase excitation drive pulse.

FIG. 11 is a principle view showing a positioning device using a step motor and a ratchet mechanism.

[Explanation of symbols]

 1a rotor 1e coil 1f coil 15 drive ring 17 lens drive ring 17c ratchet click 19 ratchet lever MD motor driver

Claims (2)

[Claims] 1. A step motor capable of rotating in the normal and reverse directions, a driving member connected to the step motor and traveling in both the forward and reverse directions corresponding to a rotation direction of the step motor, and a driving member when the driving member travels in the forward direction. The position member driven by the driving member and the excitation state of the step motor are sequentially updated, and the step motor is rotated in the forward direction up to the target Nth step, and then the excitation state of the step motor is updated. And a motor control means for reversing the step motor to rotate the step motor in the reverse direction, and the position member for the N position when the traveling direction of the drive member is switched from the forward direction to the reverse direction.
In a positioning device provided with a locking member that locks at a locking point corresponding to the step eye, the motor control means, when rotating the step motor from the (N-1) th step to the Nth step, performs the N-1 step. The excitation state corresponding to the eyes and the excitation state corresponding to the Nth step are alternately repeated a plurality of times, and the duty ratio of the excitation state corresponding to the Nth step is finally increased to 100%. Positioning device using a step motor as a drive source. 2. A step motor capable of rotating in the forward and reverse directions, a drive member connected to the step motor and traveling in both the forward and reverse directions corresponding to the rotation direction of the step motor, and when the drive member travels in the forward direction. The position member driven by the driving member and the excitation state of the step motor are sequentially updated, and the step motor is rotated in the forward direction up to the target Nth step, and then the excitation state of the step motor is updated. A motor control means for reversing the step motor to rotate the step motor in the reverse direction, and a driven member which is operated in association with the traveling of the driving member after the traveling direction of the driving member is switched from the forward direction to the reverse direction. A positioning device including a locking member that locks the position member at a locking point corresponding to the Nth step when the traveling direction of the drive member is switched from the forward direction to the reverse direction When the step motor is rotated from the (N-1) th step to the Nth step, the motor control means alternates between an excited state corresponding to the (N-1) th step and an excited state corresponding to the Nth step. A positioning device using a step motor as a drive source, wherein the duty ratio in the excited state corresponding to the Nth step is increased to 100% in the end while repeating the above multiple times.