JP2627154B2 - Step motor driven program shutter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to an improvement of a step motor drive program shutter in which a step motor is also used as a drive source to drive a shutter blade which also serves as an aperture blade, and particularly to a step shutter capable of improving closing response and adapting to high-speed exposure seconds. The present invention relates to a motor-driven program shutter.

[Prior art]

First, FIG. 7 shows a program shutter using a conventionally known step motor as a drive source. In the drawing, 50 is a blade drive ring, 51 is a lens drive ring, and both rings 50 and 51 are supported concentrically so as to be rotatable around an aperture 52. A gear surface 50 a is formed on the blade drive ring 50, and the gear surface 50 a meshes with the gear 53. A gear 54 coaxial with the gear 53 meshes with a shaft 55 of a step motor (not shown), and the blade drive ring 50
Rotates left and right. The blade drive ring 50 has a cam surface 50b.
The boss 56a of the interlocking cam 56 is in contact with 0b. Therefore,
When the blade drive ring 50 is rotated clockwise from the state shown in the figure, the interlocking cam 56 rotates counterclockwise around the shaft 56b while the boss 56a contacts the cam surface 50b. The clockwise rotation causes the shutter blade to operate in the opening direction, and the clockwise rotation of the interlocking cam 56 causes the shutter blade to operate in the closing direction. The lens drive ring 51 is urged clockwise by a spring 57, but the pin 51a implanted in the lens drive ring 51 abuts the step 50c at the end of the cam surface 50b to limit the clockwise rotation. Have been. Therefore, when the blade drive ring 50 rotates clockwise, the lens drive ring 51
The pin 51a rotates clockwise while abutting on the step 50c, and the rotation of the lens drive ring 51 activates, for example, a helicoid or other focus adjustment mechanism. A gear 5 is provided on a gear surface 51b formed on the lens drive ring 51.
8 meshes, and a ratchet 59 is provided coaxially with the gear 58. Reference numeral 60 denotes an iron piece lever for engaging the ratchet 59. The iron piece lever 60 is urged clockwise by a spring 61, but is initially attracted to the magnet 62 to limit clockwise rotation. Have been. When the lens driving ring 51 rotates clockwise with the clockwise rotation of the blade driving ring 50, and a control circuit (not shown) demagnetizes the magnet 62 by a signal generated at the time of focusing, the iron lever 60 Is rotated clockwise by the spring 61 to engage the ratchet 59, and the engagement of the ratchet 59 stops the lens drive ring 51, thereby positioning the photographic lens (not shown). Even after the lens drive ring 51 stops, the blade drive ring 50 continues to rotate, and its cam surface 50b rotates the interlocking cam 56 counterclockwise, whereby a shutter blade (not shown) starts opening operation. When the motor shaft 55 is reversed after the desired exposure time has elapsed, the blade drive ring 50 rotates counterclockwise, and the interlocking cam 56 rotates clockwise while the boss 56a contacts the cam surface 50b. Then, the shutter blade (not shown) is closed to end the exposure operation. When the step 50c of the blade drive ring 50 comes into contact with the pin 51a, the lens drive ring 51 also rotates counterclockwise and the lens mechanism returns to the initial position.

[Problems to be solved by the invention]

When the stepping motor is used as the driving source as described above, the shutter blades are opened by the forward rotation of the stepping motor, and the shutter blades are closed by the reversing operation of the stepping motor. And it is difficult to cope with high-speed exposure seconds. Also, since both opening and closing operations are pulse controlled,
In order to increase the exposure accuracy, it is necessary to accurately control the inversion of the pulse phase at the time of shifting from the opening operation to the closing operation, and there has been a problem that the pulse control circuit becomes complicated.

[Means for solving the problems]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a step motor driven program shutter which is excellent in closing response and in which a transition from an opening operation to a closing operation requires only mere timing control. And The above object of the present invention is achieved by the following means. The program shutter driven by the step motor according to the present invention includes: a step motor (25) rotatable in both forward and reverse directions:
A blade drive ring (1) to which the rotation of the step motor is transmitted and which is driven to rotate in both forward and reverse directions; and directly or indirectly connected to the shutter blades, for driving the shutter blades to open and close according to the operating direction; A blade drive cam (1) to which a biasing force in the direction of closing the shutter blade is constantly applied.
7) and: The blade drive cam is supported by a shaft on the blade drive ring so as to be swingable, and the blade drive ring rotates forward in a state where the swing angle relative to the blade drive ring is fixed. Cam interlock lever (15) formed with a cam surface (15) b for driving the lever in the opening direction against the urging force
And: an iron piece member (13) for fixing the relative swing angle of the cam interlocking lever with respect to the blade drive ring by magnet excitation; and: releasing the lock of the cam interlocking lever by the iron piece member by magnet demagnetization to release the shutter blade. And exposure end timing control means for operating the shutter in the closing direction by the urging force.

[Action]

In the present invention, a blade driving cam for opening and closing the shutter blades is always provided with a biasing force in a direction to close the shutter blades, and a cam surface for driving the blade driving cam is formed on a cam interlocking lever. ing. The cam interlocking lever is swingably supported on a shaft on the blade driving ring, but the relative swing angle of the cam interlocking lever with respect to the blade driving ring is fixed by an iron piece lever with magnet excitation, and the blade of the cam interlocking lever is fixed. If the blade drive ring rotates forward with the relative swing angle with respect to the drive ring fixed, the blade drive cam operates in the opening direction against the urging force in the closing direction in the process. Then, if the fixing of the cam interlocking lever is released by demagnetizing the magnet at the timing when the desired exposure time is obtained, the blade driving cam closes the shutter blade by the urging force in the closing direction. As described above, in the present invention, the closing responsiveness is determined by the urging force applied to the blade driving cam in the direction to close the shutter blade, and the closing responsiveness is not related to the rotation speed of the stepping motor. It is easier to respond to high-speed exposure seconds. Further, the control of the inflection point from the opening operation to the closing operation may be performed only by controlling the operation timing of the magnet, and the reversal of the step motor is merely the operation of returning the shutter mechanism to the initial position. It is good with a simple one just inverting.

【Example】

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. First, FIGS. 1, 2 and 3 are plan views showing one embodiment of the present invention. FIG. 1 shows an initial state, FIG. 2 shows a state in which a shutter is fully opened, and FIG. The time is shown respectively. In FIGS. 2 and 3, some of the elements shown in FIG. 1 are omitted in the drawings to avoid complication of the drawings. In the drawing, a blade drive ring 1 rotatably supported along the periphery of an aperture 2 has a gear surface 1a, and rotation of a shaft 3 of a step motor is supported coaxially with a gear 4, a gear 4. The power is transmitted to the gear surface 1a via the gear 5.
In this embodiment, it is assumed that shutter blades (not shown) are opened by clockwise rotation of the blade drive ring 1. Next, reference numeral 6 denotes a lens driving ring connected to a helicoid or other focusing mechanism. The lens driving ring 6 is urged clockwise by a spring 26.
6a is in contact with the locking member 1b implanted in the blade drive ring 1 to restrict the rotation. The lens drive ring 6 has a gear surface 6b.
A ratchet wheel 8 is axially supported coaxially with a gear 7 meshing with 6b. Next, reference numeral 9 denotes a ratchet click which is swingably supported on the shaft 10, and a claw 9a formed at one end of the ratchet click 9 rides on the shelf 8a of the ratchet wheel 8 in the initial state. The radius of 8a is the ratchet part 8b
Is larger than the radius. The other end of the ratchet click 9 is formed with an engagement protrusion 9b. The engagement protrusion 9b is inserted into an engagement groove 12a formed at one end of the movable iron piece 12, and the movable iron piece 12 is formed of an iron piece member. It is movably held by an iron piece lever 13 as an example. As shown in the perspective view of FIG. 4, the iron lever 13 is swingably supported by a shaft 14 and has hook-like holding portions 13a above and below its longitudinal end. Movable iron piece in part 13a
12 is inserted movably in the direction of arrow A. And
The engagement projection 9b of the ratchet click 9 is inserted into an engagement groove 12a formed in the movable iron piece 12, and the ratchet click 9 is urged clockwise by a spring 11. A boss 13c for fixing the relative position of the cam interlocking lever 15 with respect to the blade drive ring 1 is formed at the tip of the arm 13b extended from the iron piece lever 13. As shown in FIG. 1 to FIG.
Is swingably supported by a shaft 16 on the blade drive ring 1 and has a cam surface 15a protruding in a substantially concentric arc shape on the back surface thereof.
And a cam surface 15b which is inclined and raised.
When the tip of the cam interlock lever 15 reaches the position of the boss 13c with the clockwise rotation of the blade drive ring 1, the cam surface 15a engages with the boss 13c, and the cam interlock lever 15 rotates counterclockwise. Is restricted, and the relative position of the cam interlock lever 15 with respect to the blade drive ring 1 is fixed. Reference numeral 17 denotes a blade driving cam. The blade driving cam 7 is rotatably supported by a shaft 18 fixed to the camera body, and is urged clockwise by a spring 19; The clockwise rotation is restricted by the stop mechanism in the state shown in FIGS. This blade drive cam
A boss 17a is implanted on the surface of 17 and when the cam surface 15b at the rear end of the cam interlocking lever 15 reaches the position of the boss 17a as the blade drive ring 1 rotates clockwise, the cam surface 15b The blade drive cam 17 is rotated counterclockwise against the spring 19. The blade drive cam 17 is connected to a shutter blade (not shown). The counterclockwise rotation of the blade drive cam 17 opens the shutter blade, and closes the shutter blade by the clockwise rotation of the blade drive cam 17. It has been done. 20 is a magnet for driving the iron piece lever 13, 21
Indicates an iron core of the magnet 20. The only control operations required in the above-described shutter mechanism are forward / reverse rotation of the step motor connected to the axle 3 and on / off control of the magnet 20. This control is a simple control system as shown in FIG. It is executed in. In FIG. 5, reference numeral 20 denotes the above-described magnet, reference numeral 22 denotes a release switch that generates a release signal RS in conjunction with a shutter button (not shown), and reference numeral 23 denotes a focus detection signal AF when the photographing lens reaches a focus position. The well-known focus detection unit 24, which incorporates a light receiving element and an optical integrator, has a built-in light receiving element and an optical integrator, and receives the AE start signal AES indicating the start point of the exposure integration operation. A known exposure control unit 25 for generating an AE end signal AEE indicating an exposure end point, a stepping motor 25 connected to the known axle 3 and a control unit 26 having a microcomputer for controlling the above elements are respectively shown. The details of the control operation of the control device 26 will be described later. Next, the operation of this embodiment will be described with reference to the above items and the flowchart of FIG. First, in an initial state, the mechanism of the present invention is shown in FIG. In this state, when the release switch 22 generates a release signal RS in conjunction with turning on of the shutter button, the controller 26 excites the magnet 20 and rotates the step motor 25 forward. The rotation direction of the step motor 25 is determined by the phases of the A-phase pulse φa and the B-phase pulse φb, and the rotation speed of the step motor 25 is determined by the pulse period of both pulses. First, with the excitation of the magnet 20, the movable iron piece 12 is magnetically attached to the iron core 21 together with the iron piece lever 13. Further, since the engagement projection 9b of the ratchet click 9 is engaged with the engagement groove 12a of the movable iron piece 12, the ratchet click 9 is also fixed in the state shown in FIG. On the other hand, the forward rotation of the step motor 25 causes the axle 3 to rotate clockwise one pitch at a time, and the gears 4 and 5 to rotate counterclockwise. Then, the rotation of the gear 5 is transmitted to the gear surface 1a, and the blade drive ring 1 rotates clockwise by one pitch. However, even if the blade driving ring 1 starts to rotate clockwise in this manner, the blade driving cam 17 is kept in a spring until the cam surface 15b of the cam interlocking layer 15 reaches the position of the boss 17a of the blade driving cam 17. Since the state of FIG. 1 is maintained by the tension of 19, the shutter blade (not shown) is in the closed state. Now, the locking member 1b for locking the lens drive ring 6
Is implanted on the blade drive ring 1, the lens drive ring 6 rotates clockwise by the tension of the spring 26 while the step 6a abuts on the locking member 1b as the blade drive ring 1 rotates. Then, the focus adjustment mechanism (not shown) is driven by the rotation of the lens drive ring 6, and the focus detection unit 23 generates a focus detection signal AF at a point where the photographing lens has moved to the focus position, and the control device 26 sets the focus detection signal AF. When the focus detection signal AF is received, the magnet 20 is demagnetized. On the other hand, the clockwise rotation of the lens drive ring 6 causes the gear 7 meshing with the gear surface 6b to rotate counterclockwise, and the ratchet wheel 8 coaxial with the gear 7 also rotates counterclockwise. Then, since the movable iron piece 12 is released from the iron core 21 of the magnet 20 at the timing when the magnet 20 is demagnetized, the ratchet click 9 is rotated clockwise by the spring 11 and its claw 9a is moved to one of the ratchet parts 8b. To stop the rotation of the ratchet wheel 8. Therefore, the rotation of the lens drive ring 6 is also stopped at that time, and the taking lens (not shown) is positioned at that position. When the positioning of the taking lens is completed in this manner, the cam surface 15b of the cam interlocking lever 15 has not reached the position of the boss 17a of the blade driving cam 17, and the blade driving cam 17 is in the state shown in FIG. The shutter blades (not shown) are not opened because of the presence. By the way, the step motor 25 further continues the normal rotation operation, and the tip of the cam interlock lever 15 reaches the position of the boss 13c. Immediately before the tip of the cam interlocking lever 15 reaches the position of the boss 13c, the control device 26
And the iron lever 13 is rotated clockwise to be magnetically attached to the iron core 21. Therefore, the gum interlocking lever 15 has its cam surface 15
a is inside the boss 13c (the side facing the center of aperture 2)
The rotation of the cam interlocking lever 15 is restricted by the boss 13c in the counterclockwise direction, and the position relative to the blade drive ring 1 is fixed. At this time, the movable iron piece 12 is also magnetically attached to the iron core 21, but since the ratchet click 9 is urged clockwise by the spring, the ratchet wheel 8 is maintained in a locked state. When the cam surface 15b of the cam interlocking lever 15 reaches the position of the boss 17a as the stepping motor 25 continues to rotate forward, the blade drive cam 17 causes the spring 19 to contact the spring 19 while the boss 17a contacts the cam surface 15b. The shutter blade rotates counterclockwise to actuate the shutter blade in the opening direction. When the AE start position (the position for activating the exposure control unit 24) is reached immediately before the shutter blade becomes a pinhole, the control unit 26 adds the AE start signal AES to the exposure control unit 24 and integrates the field light. Start the operation. After the operation of the exposure control unit 24 starts, when the integrated value of the field light reaches a predetermined value, the exposure control unit 24 generates an AE end signal AEE, and the control device 26A turns on the magnet 20 when the AE end signal AEE is received. Degauss. AE end signal when the brightness is low
Since the aperture 2 is fully opened before the occurrence of the AEE, and the exposure for a longer time causes camera shake, the control device 26 sets the A to a predetermined time after the generation of the AE start signal AES.
E Demagnetize the magnet 20 regardless of the presence or absence of the end signal AEE. Therefore, the control device 26 functions as exposure end timing control means. FIG. 2 shows a state in which the blade drive ring 1 has been rotated to the fully opened position of the aperture 2, and the cam surface 15b has rotated the blade drive cam 17 to the leftmost position. When the magnet 20 is demagnetized in the state of FIG. 2 as described above, the iron piece lever 13 is released from the magnetic attachment by the iron vibration 21, and the fixing of the cam interlocking lever 15 by the boss 13c is released. Therefore, the blade drive cam 17 is instantaneously rotated clockwise by the spring 19 while the boss 17a rotates the cam interlocking lever 15 counterclockwise, and the blade drive cam 17 rotates the shutter (not shown) by the clockwise rotation. The blades operate in the closing direction. FIG. 3 shows a state in which the closing operation of the shutter blade has been completed in this manner. After the closing delay time of the shutter elapses after the magnet 20 is turned off, the control device 26 reverses the phase of the A-phase pulse φa and the B-phase pulse φb to rotate the step motor 25 in the reverse direction. When the stepping motor 25 rotates in the reverse direction, the ratchet click 9 has already been released from the magnet core 21 at this point, so that the locking member 1b rotates the lens driving ring 6 counterclockwise while the blade driving ring 1 also rotates counterclockwise. It rotates around and returns to the initial position shown in FIG. In the above, an example is shown in which the lens driving ring is rotated following the rotation of the blade driving ring, and the cam interlocking lever is fixed and released by diverting the magnet for positioning the lens driving ring. However, the driving source of the photographing lens may be obtained from a device other than the step motor.

【effect】

As described above, in the case of the present invention, the relative position of the cam interlocking lever with respect to the blade drive ring is fixed by the magnet drive during the opening operation of the blade, so that the shutter blade is rotated by the rotation of the blade drive ring by the step motor. Will operate in the opening direction, so that the opening characteristics of the shutter blades are determined depending on the stepping motor. Conversely, during the closing operation of the blade, the fixing of the cam interlocking lever is released, and the blade operates in the closing direction by driving the spring. Therefore, the closing response of the blade is determined depending on the spring. As described above, according to the present invention, the blades are driven by the step motor at the time of opening, so that the opening characteristics can be ideally controlled. At the time of closing, the connection with the step motor is cut off and the spring is restored, so that the closing is performed. It has excellent responsiveness and can sufficiently respond to high-speed exposure seconds. Further, the control of the inflection point from the opening operation to the closing operation may be performed only by controlling the operation timing of the magnet, and the reversal of the step motor is merely the operation of returning the shutter mechanism to the initial position. Only need to be inverted.

[Brief description of the drawings]

FIG. 1 is a plan view showing an initial state of a program shutter according to an embodiment of the present invention, FIG. 2 is a plan view showing a fully opened state of the program shutter shown in FIG. 1, and FIG. 3 is shown in FIG. 4 is a plan view showing the closed state of the program shutter, FIG.
FIG. 5 is a perspective view showing an iron piece lever, a movable iron piece and a ratchet click in the shutter mechanism, FIG. 5 is a block diagram of a control system of the present invention, FIG. 6 is a control flowchart of the present invention, and FIG. FIG. 9 is a plan view of a program shutter using a conventional step motor as a drive source. DESCRIPTION OF SYMBOLS 1 ... Blade drive ring, 1a ... Gear surface 1b ... Locking member, 2 ... Aperture 3 ... Motor shaft, 4, 5 ... Gear 6 ... Lens drive ring, 6b ... Gear surface 8 ... … Ratchet wheel 9… Ratchet click 9b… Engagement protrusion, 12… Movable iron piece 13… Iron piece lever, 13c… Boss 15… Cam interlocking lever, 15a / 15b… Cam surface 17… Blade driving cam , 17a ... boss

Claims (1)

(57) [Claims] 1. A step motor rotatable in both forward and reverse directions, a blade drive ring to which rotation of the step motor is transmitted and driven to rotate in both forward and reverse directions, and which is directly or indirectly connected to a shutter blade to operate. A blade driving cam that constantly opens and closes the shutter blades in accordance with a direction and that is constantly applied with a biasing force in a direction to close the shutter blades; A cam interlock having a cam surface formed to drive the blade drive cam in the opening direction against the urging force in a process where the blade drive ring performs a normal rotation operation in a state where the relative swing angle with respect to the drive ring is fixed. A lever, an iron piece member for fixing a relative swing angle of the cam interlocking lever with respect to the blade drive ring by magnet excitation, and an iron piece member by magnet demagnetization. The step motor driving program shutter comprising a exposure end timing control means for actuating the closing direction of the shutter blade by the urging force by releasing the fixing of the cam interlock lever that.