JP2016177210A - Blade driving device, optical device, and method of driving stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably drive a stepping motor that drives a diaphragm blade and the like at a high speed.SOLUTION: A blade driving device includes: a stepping motor that drives a diaphragm blade which opens and closes an opening for exposure; and a control circuit 100 that supplies a pulsed driving signal whose peak has a first voltage VDD to the stepping motor, and then supplies a pulsed driving signal whose peak has a second voltage VCC lower than the first voltage VDD to the stepping motor to drive the stepping motor.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a blade driving device, an optical device, and a stepping motor driving method.

  As a driving method of the stepping motor, there is known a driving method in which the pulse rate is suppressed at the time of starting to operate from a stationary state and the pulse rate is increased after starting to move (Patent Documents 1 to 3).

JP-A-6-88985 JP 2003-224996 A JP-A-6-262815

  When the conventional driving method for adjusting the pulse rate is applied to a stepping motor for driving a diaphragm blade or a shutter blade of a camera or the like, there is a problem that the driving speed becomes slow. For example, the exposure time of a still camera is required to be about 1/2000 second, and the diaphragm blades are required to be controlled in the same amount of time. However, if the control is performed to gradually increase the pulse rate, it takes time to drive. The driving of the diaphragm blades cannot be completed within the exposure time.

  On the other hand, when driven at a higher pulse rate than at the start, step-out occurs and the stepping motor cannot be driven stably.

The present invention has been made in view of the above circumstances, and an object thereof is to stably drive a blade member such as a diaphragm blade at high speed.
Another object of the present invention is to drive a stepping motor at high speed and stably.

The blade driving device according to the first aspect of the present invention for achieving the above object is
A stepping motor that drives a blade member that opens and closes an opening for exposure;
Providing the stepping motor with a pulsed drive signal whose peak has a first voltage and subsequently supplying a pulsed drive signal with a second voltage whose peak is lower than the first voltage; Driving means for driving the stepping motor;
Is provided.
By adopting such a configuration, the torque at the time of start-up is increased, step-out hardly occurs, and smooth start-up becomes possible.

For example, the driving unit applies a pulsed driving signal having a constant pulse rate from the start to the stop of the stepping motor.
As a result, the starting torque can be increased, so that adjustment of the pulse rate as a countermeasure for step-out becomes unnecessary or light.

The blade member includes, for example, a diaphragm blade that controls the opening of the opening for exposure.
The present invention is suitable for use in driving a blade member such as a diaphragm blade that has a high frictional resistance and requires a high-speed operation in a short time.

  The pulse drive signal is composed of, for example, a rectangular wave drive signal or a pseudo sine wave drive signal.

The driving means may further apply a pulsed driving signal having a third voltage whose peak is higher than the second voltage before stopping the application to the stepping motor.
This driving method is effective when a large torque is required even when stopped.

  An optical device according to a second aspect of the present invention for achieving the above object includes a lens, a blade member, an image sensor, and the blade driving device described above.

A stepping motor driving method according to the third aspect of the present invention for achieving the above object is as follows:
The stepping motor is provided with a pulsed drive signal having a peak having a first voltage and subsequently a pulsed drive signal having a second voltage having a peak lower than the first voltage. Drive the motor.

  According to the present invention, it is possible to drive the stepping motor at high speed and stably.

It is a figure which shows the aperture_diaphragm | restriction apparatus which concerns on Embodiment 1 of this invention, and has shown the state (open state) with the largest aperture diameter. It is a figure which shows the aperture_diaphragm | restriction apparatus which concerns on Embodiment 1 of this invention, and has shown the state (maximum aperture state) where the aperture diameter is the minimum. It is the figure which expanded a part of diaphragm | throttle device which concerns on Embodiment 1 of this invention. It is a figure which shows the aperture blade of the aperture_diaphragm | restriction apparatus which concerns on Embodiment 1 of this invention. It is the schematic of the stepping motor of the aperture_diaphragm | restriction apparatus which concerns on Embodiment 1 of this invention. It is a block diagram of the drive circuit of the diaphragm | throttle device which concerns on Embodiment 1 of this invention. It is a figure which shows the flowchart of the opening / closing operation | movement of the aperture_diaphragm | restriction apparatus which concerns on Embodiment 1 of this invention. (A)-(f) It is a figure which shows the drive signal of the aperture_diaphragm | restriction apparatus which concerns on Embodiment 1 of this invention. (A)-(d) It is a figure which shows the drive signal of the aperture_diaphragm | restriction apparatus which concerns on Embodiment 1 of this invention. (A)-(d) It is a figure which shows the other example of the drive signal of the aperture_diaphragm | restriction apparatus which concerns on Embodiment 1 of this invention. It is a block diagram of the drive circuit of the diaphragm | throttle device concerning Embodiment 2 of this invention. (A)-(f) It is a figure which shows the drive signal of the aperture_diaphragm | restriction apparatus which concerns on Embodiment 2 of this invention. It is a figure which shows the shutter unit which concerns on Embodiment 3 of this invention. It is a figure which shows the drive lever which concerns on Embodiment 3 of this invention. It is a figure which shows the shutter unit which concerns on Embodiment 3 of this invention. It is a figure which shows the principal part structure of the optical device which concerns on embodiment of this invention. It is a figure which shows the example of the micro step drive signal which controls a stepping motor.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(Embodiment 1)
Embodiment 1 in which the present invention is used for driving a diaphragm device of a camera will be described.
First, the configuration of a diaphragm device including diaphragm blades to be driven will be described with reference to the drawings.
As shown in FIGS. 1 to 3, the diaphragm device 1 that is the driving target of the driving device and the driving method according to the first embodiment includes a base plate 10 and a plurality of diaphragm blades 20 (here, 9 apertures) that adjust the aperture of the diaphragm. Sheet), a drive ring 30 for driving the plurality of diaphragm blades 20, a stepping motor 200 to be described later as a drive source of the drive ring 30, and a gear train 300 for transmitting the power of the stepping motor 200 to the drive ring 30 A control circuit 100 described later for controlling the stepping motor 200 is provided as a basic configuration.

  The base plate 10 is a disc-like support member having an opening 10a for exposure at the center, and the first and second support pins 11 and 12 for supporting the plurality of aperture blades 20 are openings. Centering on the center point of 10a, they are arranged in 40 ° rotational symmetry.

  The plurality of aperture blades 20 are members that cooperate to adjust the degree of opening of the opening 10a. As shown in FIG. 4, each diaphragm blade 20 has a one-wing shape and has a key hole 21 and a long hole 22. As shown in FIGS. 1 to 3, each aperture blade 20 has a first or second support pin 11 or 12 inserted in a key hole 21 and is pivotally supported around the key hole 21. . Thereby, the aperture blade 20 adjusts the opening degree in multiple stages from the state where the opening 10a is fully opened as shown in FIG. 1 to the state where the opening 10a is almost fully closed as shown in FIG. Is possible.

  Since the plurality of diaphragm blades 20 are in contact with each other or with the main plate 10 and the like, the contact surface contact is large, and there is a large static friction, and a constant torque is required for driving the diaphragm blades 20.

  The drive ring 30 is a ring-shaped member having an opening 10a formed at the center, and is disposed in a hollow portion formed at the center of the main plate 10. The drive ring 30 performs a diaphragm operation (or a diaphragm) on the diaphragm blade 20 by its rotation. (Cancellation operation). A rack 33 to which the rotational driving force is transmitted is provided at a part of the outer peripheral edge of the drive ring 30.

  On the upper surface of the drive ring 30, first and second drive pins 31, 32 are suspended from the central point of the opening 10 a in a 40 ° rotational symmetry. The first and second drive pins 31 and 32 are inserted into the long holes 22 of the corresponding diaphragm blades 20. As the drive ring 30 rotates, the first and second drive pins 31 and 32 slide in the long hole 22. Thereby, each aperture blade 20 rotates around the key hole 21 to adjust the aperture of the opening 10a. For example, when the plurality of diaphragm blades 20 are in positions as shown in FIG. 1, when the drive ring 30 is moved clockwise, the plurality of diaphragm blades 20 are respectively along the long holes 22 with the key hole 21 as the central axis. It rotates and each front-end | tip approaches the center of the diaphragm | throttle device 1. FIG.

  The stepping motor 200 generates power for driving the drive ring 30 to rotate, and is disposed on the main plate 10.

  As shown in FIG. 5, the stepping motor 200 includes a rotor 210 that is magnetized in a plurality of poles in the circumferential direction, an A-phase yoke 220a, a B-phase yoke 220b, and an A-phase yoke 220a disposed to face the rotor 210. And a B-phase coil 230b and a B-phase coil 230b wound around each of the B-phase yokes 220b, and the rotor 210 is rotated in the forward and reverse directions by two-phase drive signals of A-phase and B-phase. To do.

  The gear train 300 shown in FIGS. 1 to 3 transmits the rotation of the stepping motor 200 to the drive ring 30, and includes a pinion gear 310 and a two-stage gear 320 mounted on the rotation shaft of the stepping motor 200. . The two-stage gear 320 includes a large gear 321 that is pivotally supported by the base plate 10 and meshes with the pinion gear 310, and a small gear 322 that is disposed coaxially with the large gear 321 and meshes with the rack 33.

  The control circuit 100 is a circuit for driving the stepping motor 200. When the aperture is opened and closed, first, a high voltage pulse is applied to generate a large torque to start the aperture blade 200 against static friction, Subsequently, normal pulse driving with a normal voltage (a voltage lower than a high voltage) is performed.

  Specifically, the control circuit 100 is disposed on the main plate 10 and, as shown in FIG. 6, a controller 110, a storage unit 111, a timer 120, an aperture position sensor 130a, a rotor position sensor 130b, and a drive signal generation. A circuit 140, an A-phase driver 150a, a B-phase driver 150b, and a switch 160 are provided.

  The controller 110 includes a processor and the like, executes a control program stored in the storage unit 111, controls the drive signal generation circuit 140 when the aperture blade 20 is opened and closed, and generates a rectangular wave drive signal, Further, the switch 160 is controlled to generate a high-voltage VDD pulse in half of the first pulse period of the drive waveform, and thereafter, a VCC pulse lower than VDD is generated. Details of the control will be described later.

  The storage unit 111 stores constants and control programs used for the operation of the controller 110.

  The timer 120 operates according to the control of the controller 110 and measures a period of 1/4 of the period T of the drive pulse.

The aperture position sensor 130 a is configured by a Hall element or the like, detects the current aperture position of the aperture blade 20, and supplies a signal indicating the detected position to the controller 110.
The rotor position sensor 130b is configured by a Hall element or the like, detects the position of the rotor 210 of the stepping motor 200, and supplies a signal indicating the detected position to the controller 110.

  The drive signal generation circuit 140 generates rectangular wave drive signals for the A phase and B phase of the stepping motor 200 in accordance with the control of the controller 110.

The A-phase driver 150a includes a level conversion circuit, converts the level of the A-phase drive signal supplied from the drive signal generation circuit 140 into a drive voltage system signal applied via the switch 160, and the stepping motor 200. Applied to the A-phase coil 230a.
The B-phase driver 150b includes a level conversion circuit, converts the level of the B-phase drive signal supplied from the drive signal generation circuit 140 into a drive voltage system signal applied via the switch 160, and the stepping motor 200. Applied to the B-phase coil 230b.

  The switch 160 is composed of a semiconductor switch or the like, and selects one of the voltage VDD and VCC (VDD> VCC) and supplies it as an operating voltage to the A-phase driver 150a and the B-phase driver 150b. In this embodiment, the switch 160 selects the voltage VDD for a period of T / 4 (T is one cycle of the drive signal) after the stepping motor 200 is activated, and then selects the voltage VCC. The switch 160 is switched under the control of the controller 110.

  Next, the opening / closing operation of the diaphragm device 1 having the above configuration will be described with reference to the flowchart shown in FIG. 7 and the waveform diagram shown in FIG.

  In the following description, for easy understanding, the aperture portion 10a is divided into 21 stages from the open state of FIG. 1 to the maximum throttle state of FIG. The first stage and the maximum aperture state are the 21st stage. In addition, the aperture position sensor 130a sequentially detects what stage the aperture positions of the plurality of aperture blades 20 are currently in, and notifies the controller 110 of the detected number of stages.

When an instruction signal for instructing the aperture, f value, etc. of the aperture is supplied from an external device (not shown), the controller 110 starts the aperture control process shown in FIG.
First, the controller 110 identifies the number of stages of the diaphragm blades 20 from the output signal of the diaphragm position sensor 130a, and further identifies the stop position (rotation angle) of the rotor 210 from the output signal of the rotor position sensor 130b. (Step S11).
Subsequently, the controller 110 specifies the number of steps that the diaphragm blade 20 should move from the current position of the diaphragm blade 20 to the number of steps corresponding to the opening degree indicated by the instruction signal (step S12).
Next, the controller 110 specifies the direction in which the stepping motor 200 should rotate (step S13).

  Next, the controller 110 controls the switch 160 to select a relatively high voltage VDD (step S14). As a result, the voltage VDD is applied to the A-phase driver 150a and the B-phase driver 150b.

  Next, the controller 110 activates the drive signal generation circuit 140 and starts generating the drive signal so that the stepping motor 200 rotates in the rotation direction designated in step S13 (step S15). In accordance with an instruction from the controller 110, the drive signal generation circuit 140 generates rectangular wave drive signals for A phase and B phase at a constant pulse rate, for example, as shown in FIGS. 8 (a) and 8 (b). Output.

The A-phase driver 150a converts the level of the A-phase drive signal shown in FIG. 8A supplied from the drive signal generation circuit 140 into a drive voltage system signal having the voltage VDD as a pulse height, and converts the level of FIG. c) A phase A drive signal A shown in (d) is generated, A phase and its inverted signal XA are generated, and applied to the A phase coil 230a of the stepping motor 200.
The B-phase driver 150b converts the level of the B-phase drive signal shown in FIG. 8B supplied from the drive signal generation circuit 140 into a drive voltage system signal having the voltage VDD as a pulse height, and converts the level in FIG. e) A B-phase drive signal B and its inverted signal XB shown in (f) are generated and applied to the B-phase coil 230b of the stepping motor 200. The stepping motor 200 starts to rotate against static friction with a relatively large torque by a high voltage drive signal (pulse signal).

  Further, the controller 110 causes the timer 120 to start measuring T / 4 in step S15 (step S15).

  In this state, the controller 110 waits for a notification of T / 4 timing from the timer 120 (step S16).

The timer 120 measures the time from the start-up, and repeats the determination and waits when measuring less than T / 4 (step S16; No). When T / 4 or more is counted from the start, the controller 110 is notified of the end of the timing (Step S16; Yes). In response to the notification, the controller 110 controls the switch 160 to select the voltage VCC (step S17).
By switching the selection voltage of the switch 160, the A-phase driver 150a thereafter uses the A-phase drive signal supplied from the drive signal generation circuit 140 as the A-phase drive signal A having the voltage VCC as a pulse height and its inverted signal. XA is generated and applied to the A-phase coil 230a of the stepping motor 200. Similarly, the B-phase driver 150b generates a B-phase drive signal B having a pulse height of the voltage VCC and an inverted signal XB, and applies the B-phase drive signal to the B-phase coil 230b. Since the stepping motor 200 has already started to rotate, the frictional resistance is dominated by dynamic friction smaller than static friction, and the stepping motor 200 continues to rotate stably.

  The controller 110 monitors the output signal of the aperture position sensor 130a, determines whether or not the aperture blade 20 has reached the target position specified in step S11 (step S18), and the aperture blade 20 is specified in step S12. If the target position has not been reached, the determination is repeated and the process waits (step S18; NO). When it is determined that the diaphragm blade 20 has moved to the stop position (step S18; YES), the controller 110 stops the outputs of the A-phase driver 150a and the B-phase driver 150b (step S19).

  Thus, the aperture blade 20 reaches the instructed target position, and the target opening degree and f value are obtained.

  As described above, according to the diaphragm device and the driving method thereof according to the present embodiment, the first peak appears in the stepping motor 200 at the stage where the static friction at the start of driving is large and a large driving torque is required. A pulsed drive signal having a voltage VDD of 1 is supplied. When a period of ¼ of the cycle T of the drive signal has elapsed since the start, a pulsed drive signal having a second voltage VCC whose peak is lower than the first voltage VDD is supplied thereafter, and is relatively small. However, the stepping motor 200 is driven at a constant pulse rate with sufficient torque. Thereby, it is not necessary to perform control for prolonging the time required for opening and closing the aperture, such as reducing the pulse rate at the time of activation.

  Note that the voltage VCC is set to a voltage at which the stepping motor 200 cannot be normally started due to lack of energy, step-out, etc., when a drive signal having a peak voltage VCC is applied from the start. Also good.

In the above embodiment, the example in which the high voltage VDD is selected and the stepping motor 200 is started with a high pulse for a period of ¼ of the cycle T of the drive signal has been described. It is arbitrary whether or not to perform the driving in accordance with the characteristics of the diaphragm blades 20 serving as a load.
For example, i) a predetermined fixed time from the start is measured with a timer and driven with VDD until the fixed time is measured, ii) is driven with VDD for a predetermined number of steps from the start, iii) the rotor 210 is driven Driving with VDD until reaching a predetermined position, iv) Driving with VDD until the diaphragm blade 20 reaches a predetermined position may be performed. As an example, in FIGS. 9A to 9D, i) a predetermined period T from the start is measured by a timer and one period is measured, or ii) the drive is performed by VDD for one step from the start. The example of the waveform of the drive signal in case is shown.

In the above description, the drive waveform is a rectangular waveform only at the time of start. However, since a large braking torque is required even at the time of stop, for example, as shown in FIG. 10, a rectangular wave drive signal is applied even at the time of stop. do it.
In this case, for example, i) a timer or the like is obtained that is a predetermined time before the scheduled stop timing, and thereafter it is driven with VDD until the stop, and ii) the number of steps from the start is measured and determined in advance. After measuring the number of steps that have been driven, drive with VDD, iii) drive with VDD after the rotor 210 has reached a predetermined position, iv) with the diaphragm blades 20 in a predetermined position After reaching, it may be driven by VDD. As an example, FIGS. 10A to 10D show examples of waveforms of drive signals in the case of driving with a high voltage VDD during a period T / 4 immediately before stopping. Note that the peak voltage of the rectangular wave drive signal applied at the time of stop does not need to be VDD, but may be higher than VCC.

(Embodiment 2)
In the first embodiment, the example in which the voltage applied to the driver is switched between VDD and VCCC has been described. The present invention is not limited to this, and the method of generating the applied voltage is arbitrary as long as the stepping motor 200 can be driven with a high voltage pulse at the start and then driven with a low voltage pulse.

  For example, the power supply voltage VDD is applied to each driver circuit, and at the time of starting, a chopper control is performed with a step-down rate of R1% to generate a drive signal, and then a chopper with a step-down rate of R2% (R2 <R1) The drive waveform may be generated by control.

An example of the control circuit 100 in such a configuration is shown in FIG.
In this configuration example, the A-phase driver 151a and the B-phase driver 151b are composed of a step-down chopper circuit that steps down the common voltage VDD.
The controller 110 instructs the A-phase driver 151a and the B-phase driver 151b for the step-down rate R1 for a predetermined period immediately after starting and stopping of the stepping motor 200.

  The A-phase driver 151a chops the voltage VDD at the duty ratio R1 while the A-phase drive signal shown in FIG. 12A is at the H level, and outputs the chopper voltage A shown in FIG. The voltage VDD is chopped at the duty ratio R1 during the period in which the phase drive signal is at the L level, and the chopper voltage XA shown in FIG. The B-phase driver 151b chops the voltage VDD at the duty ratio R1 while the B-phase drive signal shown in FIG. 12B is at the H level, and outputs the chopper voltage B shown in FIG. The voltage VDD is chopped with the duty ratio R1 during the period in which the phase drive signal is at the L level, and the chopper voltage XB shown in FIG.

After that, when the timer 120 measures a certain period (T / 2 in the figure), the controller 110 instructs the step-down rate R2 to the A-phase driver 151a and the B-phase driver 151b. R2 <R1.
The A-phase driver 151a chops the voltage VDD at the duty ratio R2 while the A-phase drive signal shown in FIG. 12A is at the H level, and outputs the chopper voltage A shown in FIG. The voltage VDD is chopped at the duty ratio R2 while the phase drive signal is at the L level, and the chopper voltage XA shown in FIG. 11 (d) is output. The B-phase driver 151b chops the voltage VDD at the duty ratio R2 while the B-phase drive signal shown in FIG. 12B is at the H level, and outputs the chopper voltage B shown in FIG. The voltage VDD is chopped at the duty ratio R2 while the phase drive signal is at the L level, and the chopper voltage XB shown in FIG.
According to this driving method, different driving voltages can be generated from one voltage VDD.

(Embodiment 3)
The stepping motor driving apparatus and method according to the present invention are not limited to driving a diaphragm device, but can be applied to various devices, for example, a shutter unit for a camera.
Hereinafter, a shutter unit for a camera driven by the above-described stepping motor driving method will be described with reference to the drawings.

  As shown in FIG. 13, a shutter unit 500 according to Embodiment 3 includes a base 511 having an exposure opening, four shutter blades 513 (513A to 513D) for opening and closing the exposure opening, and a stepping motor. 514, a drive pin 515 driven by a stepping motor 514, and a drive lever 516 that transmits movement from the drive pin to the shutter blades.

  The base 511 is a disk-shaped support member to which the shutter blades 513 (513A to 513D), the stepping motor 514, and the like are attached, and a circular exposure opening 512 is formed at the center.

  The shutter blades 513 </ b> A to 513 </ b> D are sheet-like members that cooperate to open and close the opening for exposure 512, and are composed of a light-impermeable film member. The shutter blades 513A to 513D are provided with holes 523A to 523D at the bases thereof. The shafts 522A to 522D suspended from the base 511 pass through the holes 523A to 523D, and the shutter blades 513A to 513D can swing around these shafts 522A to 522D as fulcrums. Further, in the vicinity of the base part of the shutter blades 513A to 513D, through holes 524A to 524D through which the operation pins 525 provided on the drive lever 516 pass are provided.

  Further, since the shutter blades 513A to 513D are in contact with each other or with the base 511 and the like, they have a large contact surface contact and a large static friction, and a constant torque is required for driving them.

The stepping motor 514 is a motor similar to the stepping motor 200 shown in FIG. 5, and is rotationally driven by a drive signal input from the control circuit. The stepping motor 514 includes a driving arm 535 and drives a driving pin 515 that drives the shutter blade 513.
The drive arm 535 has a central hole fitted to the rotation shaft 533 of the stepping motor 514 at the base portion, and swings around the rotation shaft 533 by the rotation of the rotor. A driving pin 515 inserted through a long hole 517 of the driving lever 516 is fixed to the distal end portion of the driving arm 535.
As shown in FIG. 15, the stepping motor 514 is provided on the base 511 so that the rotation shaft, the drive pin 515, and the shaft 542 are positioned on a straight line when the shutter blade 513 is fully closed. . Thereby, the drive pin 515 slides in the long hole 517 in one direction when closing the shutter blade 513. The stepping motor 514 has a rotational range limited by a drive signal from the control circuit so that the rotor reciprocates at a predetermined angle.

  Returning to FIG. 13, the drive lever 516 is a member that transmits movement from the drive pin 515 to the shutter blade 513, and has a hole 541 at the center. A shaft 542 suspended from the base 511 passes through the hole 541, and the drive lever 516 can swing about the shaft 515 as a fulcrum. The drive lever 516 has an operation pin 525 at one end. The operation pin 525 is inserted through through holes 524A to 524D provided in the vicinity of the roots of the shutter blades 513A to 513D. The drive lever 516 has a long hole 517 at the other end. A drive pin 515 passes through the long hole 517.

  As shown in FIG. 14, the long hole 517 has a cam-shaped curved portion 536 at a portion where the drive pin 515 slides when the drive pin 515 closes the shutter blade 513. The shape of the long hole 517 is not limited to this, and may be a straight long hole, for example. Further, when the drive pin 515 opens the shutter blade 513, a linear portion 537 is provided at a portion where the drive pin 515 slides.

  Next, the opening / closing operation of the shutter unit 500 according to Embodiment 3 will be described. When the shutter unit 500 is provided in a digital still camera, the exposure opening 512 is fully opened as shown in FIG. 13 in a shooting standby state. For this reason, the solid-state image sensor of the camera forms a subject image that has passed through the lens, and the subject image can be observed on the monitor.

  When the release button is pressed at the time of shooting, a reset signal is sent to the solid-state imaging device, the accumulated charges are discharged, and shooting is started by starting to accumulate new charges. Thereafter, when a predetermined exposure time has elapsed, a drive signal from the control circuit is input to the stepping motor 514, the rotor rotates clockwise, and the drive arm 535 is driven clockwise via the rotation shaft.

  Here, since the shutter blades 513A to 513D are in contact with each other or with the base 511 and the like, and have a large static friction, a large driving torque is required at the time of starting. Therefore, when a large driving torque is required, a rectangular wave driving signal is supplied to the stepping motor 514 to drive the stepping motor 514 with a large driving torque. When the driving proceeds to some extent and the dynamic friction becomes more dominant than the static friction, the stepping motor 514 is smoothly driven by supplying a rectangular wave driving signal having a small amplitude to the stepping motor 514.

  When the stepping motor 514 is driven clockwise, the drive pin 515 is driven clockwise accordingly, force is transmitted to the inner periphery of the long hole 517, and the drive lever 516 swings counterclockwise. When the drive lever 516 swings counterclockwise, power is transmitted to the shutter blade 513 from an operating pin 525 provided on the drive lever 516, and the shutter blade 513 is driven in a direction to close the exposure opening 512.

  Thereafter, as shown in FIG. 15, the shutter blade 513 contacts the stopper 552, and the exposure opening 512 is fully closed. The imaging element transfers imaging information to the storage device. When the transfer is completed, the control circuit inputs to the stepping motor 514 a drive signal in which the drive signals applied to the A-phase coil 230a and the B-phase coil 230b of the stepping motor 514 are switched from fully open to fully closed. For this reason, the rotor 210 rotates counterclockwise and causes the shutter blade 513 to open. When the exposure opening 512 is fully opened, the shutter blade 513 comes into contact with the stopper 551 and stops immediately thereafter. Then, when the output of the control circuit is stopped, it returns to the fully open state shown in FIG.

  As described above, according to the driving method of the shutter unit 500 according to the third embodiment, at the time of starting, that is, at the stage where the static friction is large and a large driving torque is required, the pulsed driving signal having a large pulse peak is supplied. Then, the stepping motor 514 is driven with a large driving torque. When dynamic friction smaller than static friction becomes dominant, a pulsed drive signal having a small peak is supplied to the stepping motor 514 to drive the stepping motor 514 at a constant pulse rate. Thereby, the shutter unit 500 can be driven at a high speed without greatly impairing the driving speed.

  The diaphragm device and the shutter unit according to the above embodiment are mounted on various optical devices. For example, FIG. 16 is a diagram illustrating a configuration of a main part of an optical apparatus such as a digital still camera equipped with the diaphragm device 1 and the shutter unit 500. The solid-state imaging device 1100 such as a CCD or a CMOS displays a subject image transmitted through the lens 1000. Convert to electrical signal. The converted electrical signal is converted into a digital signal by the A / D conversion circuit and input to the image processing circuit 1200. The image processing circuit 1200 creates image data based on the input signal and stores it in a memory such as a DRAM.

  In the optical apparatus configured as described above, for example, at the time of photographing, the diaphragm device 1 and the shutter unit 500 are driven by the stepping motor driving method described in the first and second embodiments, so that the operation speed is not slowed down. can do.

  In the example described above, an example in which a rectangular wave pulse signal is used as the drive signal (pulse signal) applied to the stepping motor 514 has been described. However, a pseudo sine wave pulse signal as illustrated in FIG. Can be applied to the coils 230a and 230b for microstep drive. Also in the case of microstep driving, as in the case of the rectangular wave, a pulsed driving signal whose peak has the first voltage is supplied, and subsequently, the peak has the second voltage lower than the first voltage. The stepping motor 514 is driven by supplying a pulsed drive signal.

  Note that the number of phases of the stepping motor is not limited to 2 and is arbitrary.

The present invention is not limited to driving the diaphragm blades and shutter blades, and can be applied to driving other various loads.
Moreover, the drive device and drive method of the present invention are not limited to the above-described embodiments, and various modifications and applications are possible. For example, switching from the above-described rectangular wave driving to microstep driving is performed only when the blade is at a predetermined position (range) where the static friction is large. In other cases, microstep driving may be performed from the beginning. Good.
In the above embodiment, the amplitude of the drive signal for the rectangular wave drive is made larger than the amplitude of the drive signal for the microstep drive, but it may be equal or smaller.

  Note that a program stored in the storage unit 111 and controlling the controller 110 may be distributed separately from the driving device.

  Although it is conceivable to continuously change the peak value of the pulse-like drive signal with the passage of time, the control becomes complicated. For this reason, as described above, it is reasonable to adjust the peak voltage in one step at the start and one step at the stop.

  The present invention can be used for driving a diaphragm member of an optical device such as a digital still camera or a video camera, or a blade member such as a shutter device.

DESCRIPTION OF SYMBOLS 1 Diaphragm | squeezing apparatus 10 Base plate 10a Opening part 11 1st support pin 12 2nd support pin 20 Diaphragm blade 21 Key hole 22 Long hole 30 Drive ring 31 1st drive pin 32 2nd drive pin 33 Rack 100 Control circuit 110 Controller 111 Storage unit 120 Timer 130a Aperture position sensor 130b Rotor position sensor 140 Drive signal generation circuit 150a A phase driver 150b B phase driver 151a A phase driver (step-down chopper circuit)
151b B phase driver (step-down chopper circuit)
160 Switches 200, 514 Stepping motor 210 Rotor 220a A-phase yoke 220b B-phase yoke 230a A-phase coil 230b B-phase coil 300 Gear train 310 Pinion gear 320 Two-stage gear 321 Large gear 322 Small gear 500 Shutter unit 511 Base 512 Exposure opening 513A to 513D Shutter blade 515 Drive pin 516 Drive lever 517 Long hole 522A to 522D, 542 Shaft 523A to 523D, 541 Hole 524A to 524D Through hole 525 Actuation pin 533 Rotating shaft 535 Drive arm 536 Bending part 537 Linear part 1000 Lens 1100 Solid-state image sensor 1200 Image processing circuit

Claims (7)

A stepping motor that drives a blade member that opens and closes an opening for exposure;
Providing the stepping motor with a pulsed drive signal whose peak has a first voltage and subsequently supplying a pulsed drive signal with a second voltage whose peak is lower than the first voltage; Driving means for driving the stepping motor;
A blade driving device comprising: The drive means applies a pulsed drive signal having a constant pulse rate from the start to the stop of the stepping motor.
The blade driving device according to claim 1. The blade member is constituted by a diaphragm blade that controls the opening of the opening for exposure.
The blade driving device according to claim 1, wherein the blade driving device is provided. The pulsed drive signal is composed of a rectangular wave drive signal or a pseudo sine wave drive signal,
The blade driving device according to any one of claims 1 to 3, wherein the blade driving device is provided. The driving means further applies a pulsed driving signal having a third voltage whose peak is higher than the second voltage before stopping the application to the stepping motor.
The blade driving device according to any one of claims 1 to 4, wherein the blade driving device is provided.   An optical device comprising a lens, the blade member, an image sensor, and the blade driving device according to any one of claims 1 to 5. Providing the stepping motor with a pulsed drive signal whose peak has a first voltage and subsequently supplying a pulsed drive signal with a second voltage whose peak is lower than the first voltage; Drive the stepping motor,
Stepping motor drive method.

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