JPH0658478B2 - Automatic aperture drive for camera with built-in motor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic diaphragm driving device that operates an automatic diaphragm mechanism by a motor built in a camera.

[Prior Art] A conventional automatic diaphragm drive device for a camera is disclosed in Japanese Patent Laid-Open No. 58-108.
520 and Japanese Patent Laid-Open No. 54-74.
Some of them are disclosed in the motor-equipped camera of Japanese Patent No. 419.

The automatic diaphragm drive device disclosed in Japanese Patent Laid-Open No. 58-108520 discloses a single-lens reflex camera with a built-in electric motor, which performs a narrowing operation of the automatic diaphragm mechanism associated with the release and an opening operation of the diaphragm after the shutter curtain travels. The respective springs are charged by the output of a motor arranged in the spool chamber or the like when the film is wound, and these energy is used. Therefore, this means requires a mechanism for holding the charged state of the spring and a complicated power transmission mechanism, which leads to an increase in cost due to an increase in the size of the camera and an increase in the number of parts. Further, the transmission energy loss of the power transmission mechanism and the energy loss due to the friction of the driving member of the spring charging mechanism and the holding mechanism are considerably large, which has led to an increase in the capacity of the power supply. Also, in order to automatically control the aperture diameter, a mechanism is used that stops the ratchet member that interlocks with the aperture drive member by using the repulsion of the electromagnet, but since the aperture drive member is operated by the charged spring force, It is necessary to prevent the error of the throttle control due to the sudden acceleration motion of the member, so that the mass of the ratchet member is increased to give the governor effect, the throttle driving member is gently accelerated and operated at a low speed, A measure is taken to reduce the control error with respect to the operation delay time of the electromagnet. However, this is one of the causes of increasing the weight and volume of the camera. As another method, considering the operation delay time of the electromagnet and the acceleration of the diaphragm driving member, a method of electrically energizing the electromagnet earlier before reaching a predetermined diaphragm value was also adopted, but it is possible to control accurately. In order to do so, it is necessary to change the energization timing to the electromagnet according to the aperture diameter to be controlled, so that the electric circuit becomes complicated and the cost is increased.

Further, in the camera with a built-in motor disclosed in Japanese Patent Laid-Open No. 54-74419, the aperture opening operation is directly performed by driving the motor instead of using a precharged spring.
Although the energy loss due to the spring drive is reduced, the throttle drive member is operated only by the spring force without the speed control member when the aperture is narrowed down, so the aperture control must always be performed during the acceleration movement of the member. It is considered that the diaphragm control accuracy is low. If an attempt is made to solve the problem on the electric circuit as described above in order to improve the control accuracy, the cost of the electric circuit is increased. Furthermore, in the initial state, it is necessary to hold the diaphragm drive member in the initial position against the diaphragm spring.
By providing a holding mechanism, the camera becomes larger and the number of parts increases.

In another conventional technique, the diaphragm driving member is always biased toward the diaphragm opening side by a spring, and when the diaphragm is narrowed down, the motor is directly driven through a gear to operate the diaphragm member while charging the spring, and when the diaphragm is opened, the motor is opened. A camera of the type in which the diaphragm driving member is released from the connection by the spring force and the diaphragm driving member is disconnected is also put into practical use.

However, in the case of this system, if a general AA type dry cell or a single type 4 dry cell is used as a battery for driving the motor, the narrowing down speed becomes very slow when the ambient temperature decreases and the battery deteriorates. This will be described with reference to the rotation speed N-torque T curve of a general DC motor shown in FIG. In FIG. 7, the horizontal axis T indicates the shaft torque of the motor, and the vertical axis N indicates the rotation speed of the motor shaft per unit time. Here, the straight line A is the characteristic when the motor is operated using a general new dry battery at room temperature. At this time, the starting torque is T ₁ and the no-load rotation speed is N ₁ . Further, when the motor shaft torque is T _M when the spring for urging the throttle to open is charged, the operating point of the motor is a
It becomes a point, and the rotation speed at that time becomes N _M. The operating speed of the diaphragm driving member has a value proportional to N _M. Next, a straight line B shows the characteristics when the motor is operated using the same battery in an environment where the temperature is about -10 ° C. Here, the starting torque T ₂ is significantly smaller than T ₁ (when the motor used in the camera is generally driven by an AA manganese battery, it becomes about half of T ₁ ) and the no-load rotation speed N ₂ has a value that is very slightly smaller than N ₁ . This is because it is theoretically known that the internal resistance of the dry cell increases significantly due to the decrease in temperature, and as a result, the starting torque of the motor is greatly reduced. When no change in the motor shaft torque T _M at the time of charging the spring where the operating point of the motor becomes point b, the rotational speed when the N _M than significantly Stop N _M '
Becomes As a result, the squeezing time is about N _M / N _M ′ times, which is a significant increase. This means that the release time lag greatly changes depending on the operating environment temperature, and when shooting a fast-moving subject such as a sports photo, it is difficult to take a photo at the timing intended by the photographer. Further, even when the battery is aged, the motor characteristics tend to be substantially the same, which causes a drawback that the release time lag changes greatly.

[Problems to be Solved by the Invention] The present invention is designed to eliminate the above-mentioned conventional drawbacks in the automatic diaphragm drive mechanism of a camera with a built-in motor, particularly in the automatic diaphragm drive mechanism of a single-lens reflex camera. Without increasing the number of points and increasing the size of the camera, the holding member for maintaining the diaphragm driving member at the initial position was abolished, and the release time lag was stabilized against the operating environment and deterioration of the battery, An object of the present invention is to provide an automatic diaphragm drive device for a camera with a built-in motor, which can improve control accuracy and energy efficiency.

[Means and Actions for Solving Problems] According to the present invention, when the diaphragm is not operating, such as in the finder observation state, the diaphragm driving member biased by the spring in the diaphragm narrowing direction is used as a motor for driving the diaphragm driving member. The throttle is held at a position where it is opened by the holding torque at the magnetically stable point, and when the throttle is narrowed down, the motor is rotated in a state of almost no load by assisting the elastic force of the spring.

[Examples] Hereinafter, the present invention will be described with reference to illustrated examples. FIG. 1 is a perspective view of an automatic diaphragm driving device for a camera with a built-in motor according to an embodiment of the present invention. The present embodiment is applied to the automatic diaphragm driving device of the single-lens reflex camera of the present invention. In FIG. 1, light that has passed through a photographic lens (not shown) and has passed through a diaphragm aperture is incident on the inside of the camera body and is moved upward by a movable reflection mirror 22 that is obliquely arranged on the photographic optical axis O at an angle of 45 °. And is transmitted and diffused to the focusing screen 40. The optical image of the focusing screen 40 is a pentaprism 41 and an eyepiece lens 4.
It can be observed as an erect image in the viewfinder through 2. Further, in the vicinity of the eyepiece lens 42, a photometric light receiving element 43 is arranged facing the exit surface of the pentaprism 41. Further, behind the movable reflection mirror 22, an aperture, a focal plane shutter, etc., which are not shown, are arranged.

The photometric light-receiving element 43 measures the subject brightness by the release operation of the camera, and the brightness information is known by the known CPU 5.
0 (see FIG. 6). In the CPU, the number of narrowing steps Δ together with the determinant information of the exposure condition set in advance.
Calculating the A _V (APEX calculated value). After that, the iron core micromotor 1 is driven. An output gear 2 is attached to an output shaft 1a (see FIG. 5 (a)) of the motor 1 via an overload preventing slip clutch 70 described later. A large-diameter spur gear 3a meshes with the output gear 2 of the motor that rotates in the direction of the arrow.
The bevel gear 3b is integrally provided in a, and the bevel gear 3b
The bevel gear 4a is engaged with b. A spur gear 4b is integrally attached to the bevel gear 4a.
A large-diameter gear of the step gear 5 is engaged with b, and a set member drive gear 6 is engaged with the small-diameter gear. Therefore, as the output gear 2 rotates in the arrow direction, the gears 3a, 3b, 4a, 4b and 5 respectively rotate in the arrow direction to transmit power and rotate the gear 6 in the arrow direction. A protrusion 6a is integrally provided on the front surface of the gear 6, and is engaged with an interlocking pin 7a that is planted on the rear surface of the gear 7 that is rotatably arranged coaxially with the gear 6. . A transmission gear 8 is in mesh with the gear 7, and a gear 9a is in mesh with the gear 8. The gear 9a is coaxially fixed with a gear 9b, and the gear 9b meshes with a gear portion 10a of a diaphragm ring 10 which is a diaphragm driving member which rotates about an optical axis O. Therefore, the rotation of the gear 7 is transmitted to the aperture ring 10 via the gear 8 and the gears 9a and 9b. A spring 11 is stretched between the aperture ring 10 and an immovable member (not shown) in the camera, and a rotational force in the direction of the arrow is applied to the ring 10, but the urging force of the spring 11 is In the initial state, the holding force of the magnetically stable position of the motor 1, that is, the holding force by so-called cogging (described later) by the rotational force greatly reduced between the output gear 2 and the gear train connecting the gear portion 10a, causes the protruding piece. 10d is held at a position where it abuts on the stop pin 25 for regulating the initial position. Also,
At this rotating position, the aperture opening switch SW1 is closed by the protrusion 10c extending from the aperture ring 10. Then, when the gear 6 rotates in the direction of the arrow in this state, the elastic force of the spring 11 causes the interlocking pin 7a to project.
Following a, the gears 7, 8, 9a, 9b and the diaphragm ring 10 rotate in the directions of the arrows, respectively, and the diaphragm opening switch SW1 is opened.

Further, the small diameter gear of the step gear 12 is engaged with the gear 8 in the camera body, and the pinion 13a constituting the aperture control member 13 is engaged with the large diameter gear, and the pinion 13a and the ratchet shaft 13c are integrated. Thus, the aperture control member 13 is configured. The ratchet shaft 13c is adapted to engage and disengage the locking claw 15b of the diaphragm locking lever 15.

The support shaft 13d, to which the ratchet shaft 13c and the pinion 13a are fixed, is provided with a diaphragm aperture detecting means composed of pulse signal generating means. This signal generating means is a slit forming member 13 integrally attached to the support shaft 13d.
b and a photo interrupter 14. The slit forming member 13b is a disk provided with a large number of notches at equal intervals, and a photo interrupter 14 formed by facing a light emitting diode and a light receiving element is provided so as to sandwich the slit portion of the slit forming member 13b. ing. As a result, the rotation of the aperture ring 10 is prevented by the gear 9
b, 9a, 8 and step gear 12 through pinion 13a
Since the slit forming member 13b is rotated, the number of digital pulse signals corresponding to the aperture diameter is generated from the photointerrupter 14 with this rotation.

The diaphragm locking lever 15 is formed of a vertically long lever, and a fulcrum near the upper part thereof is rotatably instructed by a supporting shaft 15a, and the locking claw 15b faces the ratchet wheel 13c in the middle. It is formed at the position where A charge arm 15c bent rearward is formed at an upper edge portion of the locking lever 15, and the charge arm 15c is formed.
The rigid arm portion 17a of the set lever 17 that constitutes the set member is in contact with. The center of the set lever 17 is rotatably supported by the support shaft 15a, and one arm 17b of the set lever 17 is horizontal so that it elastically behaves. And the other arm 17a extends below the charge arm 15c. Then, the other arm 17a of the plain is brought into contact with the chaji arm 15c due to the elastic tension of the auxiliary spring 18 having a weak elasticity that is stretched between the tip end portion and the immovable member.

An armchair 19 which is attracted by a release type electromagnet 20 is pivotally supported under the diaphragm locking lever 15, and the armature chair 19 is attracted by the electromagnet 20 so that the diaphragm locking lever 15 is engaged. The pawl 15b is held at a position separated from the ratchet wheel 13c. As is well known, the release type electromagnet 20 is configured by arranging a permanent magnet 20a and a magnetic bypass portion (not shown) between yokes around which a coil is wound. In a so-called combination magnet, the aperture locking lever 15 is bridged between the immovable member (not shown) in the camera body and the locking lever 15 in the initial state.
Separation spring 1 having a stronger elasticity than that of the spring 18.
It is adsorbed by the electromagnet 20 against 6.

On the other hand, as shown in FIGS. 3 (a) to 3 (c), a partially arcuate end face cam 6b is formed on the back surface of the gear 6, and the gear 6 rotates to cause an interchangeable lens to be described later. When the inner diaphragm is narrowed down to the minimum diaphragm aperture, the end face cam 6b moves the lever 21 around the support shaft 21a in the mirror-up direction via the operation pin 21c fixed to the mirror drive lever 21 (see FIG. In a), it functions to rotate clockwise). The rotary reflection mirror 22 is rotatably held around a support shaft 22a fixed to the upper portions of both side surfaces, and the flatness is lowered by a mirror down spring 23 and abuts on a mirror positioning pin 24 so as to be on the optical axis O. Is installed at an angle of 45 °. Further, a mirror drive pin 22b is fixedly planted on one side surface of the reflection mirror 22, and the clockwise rotation of the mirror drive lever 21 pushes up the pin 22b by the upper side surface portion of the lever 21 to raise the mirror. The operation is performed (see FIG. 3 (c)). The bent portion 21 of the mirror drive lever 21 is at the mirror raising completion position.
b operates the mirror up switch SW2 from the off state to the on state. This switch SW2
When is closed, the motor 1 is stopped, and at that time, the mirror drive lever 21 is held in the mirror raised position at the top dead center of the end cam 6b of the gear 6.

The above is the diaphragm drive mechanism arranged in the camera body.

Next, in the diaphragm mechanism arranged in the interchangeable lens, as shown in FIG. 1, a plurality of support pins 33a are planted at equal intervals around the optical axis O in the diaphragm case 33 which is a fixed member. The diaphragm blades 32 are pivotally supported by the support holes 32b of the respective support pins 33a. Further, the diaphragm plate 30 for operating the diaphragm blades 32 is rotatably arranged around the optical axis O, and the diaphragm plate 30 is provided with a plurality of diaphragm cam grooves 30b of a known shape. The drive pins 32a planted in the aperture blades 32 are fitted in the cam grooves 30b. There,
A bent arm portion 30a for connection, in which the camera main body extends along the optical axis O, is formed on a part of the outer circumference of the aperture plate 30, and the arm portion 30a and the inside of the lens barrel are formed. A spring 31 having a weak elasticity is stretched over an immovable member (not shown). Therefore, when the interchangeable lens is attached to the camera body, the arm 31a is constantly operated by the spring 31.
Is in contact with the upper surface of the inwardly projecting piece 10b of the diaphragm ring 10. The shape of the diaphragm cam groove 30b is formed so that the rotation angle of the bent arm portion 30a and the diaphragm aperture formed by the drive pin 32a are in a proportional relationship.

4 (a) and 4 (b) are sectional views showing the internal structure of the iron core micromotor 1. As shown in FIG. This iron core micromotor is the most common one used in small devices such as cameras. The inner circumference of the casing 1b of the motor 1 is magnetized in the thickness direction in a half-moon shape as a stator.
1 is integrally fixed. On the other hand, in the rotor, an armature core 82 of a soft magnetic material is fixed to the motor shaft 1a, and a plurality of protrusions 82a of the armature core 82,
82b and 82c respectively have armature windings 83a and 83b,
83c is wrapped around. It is known that the motor having the above structure has a magnetically stable point in the rotating direction, which is generally called cogging, when no current is applied to the armature winding. In the motor shown in FIG. 4, the permanent magnets 80 and 81 as stators have two poles, and the armature core as a rotor has three poles. The state of FIG. 4 (a) and FIG. ) There are two types of magnetic stable points,
One rotation of the rotor has 6 stable points. The holding force at the magnetically stable point is determined by the characteristics of the permanent magnets 80, 81 and the gap between the stator and the rotor, but in a general motor used for a camera, it is about a fraction of the starting torque. Has holding torque. Since the force of the spring 11 (see FIG. 1) in this embodiment is increased in speed from the throttle ring 10 to the motor 1 in the gear train, the transmission torque is inversely proportional to the square of the speed increasing ratio. Therefore, it is a fraction of the coercive force of the magnetically stable point.
Therefore, it becomes possible to stably hold the aperture ring 10 at the initial position.

5 (a) and 5 (b) are detailed views of the slip clutch 70 for preventing overload provided on the shaft of the motor 1. FIG. Fifth
In FIG. 1A, the output gear 2 is rotatably attached to the output shaft 1a of the motor 1. A slip ring 70b which is movable above and below the output shaft 1a in the axial direction and rotates integrally with the output shaft 1a in the rotating direction,
70c is provided. Furthermore, 2 as shown in the figure for the output shaft 1a.
Small-diameter portions 1c and 1d are provided at places, and retaining members 70a and 70e such as E-rings are attached. A compression coil spring 70d is wound around the output shaft 1a between the slip ring 70c and the retaining member 70e. FIG. 5 (b) shows a cross section of the output shaft 1a and the slip ring 70b, and the slip ring 70c also has the same shape. The output shaft 1a has a cutout portion 1a 'having a D-shaped cross section, and an inner peripheral portion of the slip ring 70b also has a protruding portion 70b' so as to fit into the cutout portion 1a '. Therefore, the slip ring 70b is movable in the axial direction with respect to the output shaft 1a, and its rotation is restricted in the rotational direction.
During normal operation, the rotation of the output shaft 1a causes the slip rings 70b and 70c to rotate integrally, and the spring 70d
The output gear 2 sandwiched between the slip rings 70b and 70c by the force of
It rotates together with d. However, when a sudden load or an excessive load is generated in the output gear 2, the output gear 2
A slip occurs between the slip rings 70b and 70c against the frictional force. Therefore, the motor-1 and gears can be protected from a failure due to overload. Further, the repulsion of the diaphragm ring 10 when the diaphragm ring 10 rotates from the minimum diaphragm side and comes into contact with the stopper pin 25 can be suppressed. This is because until the throttle ring 10 is suddenly stopped by the stopper pin 25, the slip clutch 70 slips, so that the inertia energy due to the rotation of the motor 1 is largely released from the gear train and the motor 1 is stopped. This is because only the torque due to the dynamic friction of the slip clutch 70 is continuously transmitted to the throttle ring 10.

Thus, the automatic diaphragm drive device of this embodiment is constructed.

Next, the operation will be described. In FIGS. 2 (a) to 2 (f), the stop control mechanism of the diaphragm drive is taken out from FIG. 1 and its operation is shown. Figure (a) shows the initial state before shooting. In this embodiment, the narrowing operation is performed by rotating the gear 6 from the initial state by about 180 ° in the arrow direction. If the electromagnet 20 does not act during the narrowing operation, the narrowing operation is performed from the full open state to the minimum full throttle state. After that, the gear 6 is further rotated by about 120 ° to perform the raising operation of the mirror. Here, the gear 6 is about 300 from the start of the narrowing down to the completion of the mirror ascent
° will rotate.

Now, when the release operation causes the motor 1 and the output gear 2 to rotate in the direction of the arrow and the aperture ring 10 to rotate in the direction of the arrow via the gear train, the aperture blade 32 starts the aperture operation with this rotation, and the aperture stage number ΔA. _When a pulse signal of a number corresponding to _V is generated from the photo interrupter 14, the electromagnet 20 is activated by a signal from the CPU.
A degaussing current in a direction that attenuates the force of adsorbing the armor chair 19 is applied to the coil of the armature chair 19, and the contraction elastic force of the separating spring 16 separates the armature chair 19 from the electromagnet 20 to rotate the diaphragm locking lever 15 around the support shaft 15a. It rotates counterclockwise and its locking claw 15b moves to the ratchet wheel 13c.
Jump between the claws and suddenly stop the rotation of the diaphragm control member 13,
The aperture size is determined. FIG. 2 (b) shows a state in which the aperture diameter is determined approximately halfway between the open aperture and the minimum aperture.

Further, since the motor 1 also rotates in the same direction thereafter, the follow-up engagement between the projection 6a and the interlocking pin 7a is released, and the gear 6 further rotates in the arrow direction. Further, when the subject is extremely bright and the like, and the aperture stop operation is performed to the minimum aperture size, the protruding piece 10d causes the minimum aperture position restriction stopper 26.
Since it abuts against (see FIG. 1), the follow-up engagement between the arrow-tension projection 6a and the interlocking pin 7a is released, and the gear 6 similarly rotates in the arrow direction. Then, the rotation of the gear 6 between about 180 ° and 300 ° from the initial state causes the movable reflecting mirror 22 to move up as shown in FIGS. 3 (a) to 3 (c). This is performed by the action of the end face cam 6b.

The protrusion 6a of the gear 6 contacts the horizontal arm 17b of the set lever 17 during the mirror raising operation, but the lever 17 rotates in the counterclockwise direction while extending the spring 18, so that the protrusion 6a is rotated as the gear 6 rotates. The engagement of the horizontal arm 17b is released. In FIG. 2C, the protrusion 6a and the horizontal arm 17b come into contact with each other while the mirror is being raised, and the spring 18 extends to separate the charge arm 15c from the other arm 17a, and the protrusion 6a and the horizontal arm 17 are separated.
The state in which the contact of b is about to be released is shown. Here, since the spring 18 is an extremely weak spring, the load on the motor by the spring 18 at this time is extremely small.

In this way, when the movable reflecting mirror 22 is completely lifted and the mirror 22 is retracted from the photographing optical path, FIG.
As shown in FIG. 3, the mirror up switch SW2 is turned on, the motor 1 is stopped, and the gear 6 is also stopped at the position where the projection 6a is separated from the horizontal arm 17b in the state shown in FIG. 2 (d).

Then, when the switch SW2 is turned on, C
The shutter front curtain starts under the control of the PU, and the travel of the shutter rear curtain is controlled by the shutter time control means. When the traveling of the shutter rear curtain is completed, the motor 1 starts reversing this time. Then, along with this, the gear train from the output gear 2 to the gear 6 operates, and each gear rotates in the direction opposite to the arrow shown in FIG. As a result, the mirror driving lever 21 is rotated counterclockwise by the elastic force of the spring 23, and the movable reflecting mirror 22 descends until it comes into contact with the positioning pin 24. Further, the switch SW2 changes from the on state to the off state. On the other hand, the protrusion 6a comes into contact with the horizontal arm 17b again, and the other arm 17a and the charge arm 15c come into contact with each other by the elastic elastic force of the spring 18, so that the diaphragm locking lever 15 is rotated clockwise around the support shaft 15a. The armature 19 is rotated to release the locking state of the locking claw 15b to the ratchet wheel 13c, and the armature 19 is attracted to the electromagnet 20 again.
After that, the horizontal arm 17b is elastically deformed as shown in FIG. 2 (e), so that the contact with the projection 6a is released.

FIG. 2 (f) shows the state immediately after the operation state of FIG. 2 (e). A state in which the set lever 17 rotates counterclockwise for a moment against the elastic force of the spring 18 by the repulsive energy stored by the elastic deformation of the horizontal arm 17b at the moment when the contact state between the projection 6a and the horizontal arm 17b is released. Is.
By this operation, the attracted state of the armature 19 and the electromagnet 20 can be reliably maintained. Explaining this in a little more detail, if the diaphragm locking lever 15 and the set lever 17 are integrally formed, the repulsive energy accumulated by the elastic deformation of the horizontal arm 17b is released when the armature chair 19 and the electromagnet 20 are released. In some cases, the armature 19 may be separated from the electromagnet 20 by acting as a strong impact on the attracting surface. Therefore, in the present invention, the armature 19
In order to maintain the adsorption state of the electrode stone 20 with high reliability,
The diaphragm locking lever 15 and the set lever 17 are separately formed, and a spring 18 having a weak elasticity is used to connect them to each other so that the repulsive energy of the lever 17 is not transmitted to the lever 15.

In this way, the gear 6 continues to rotate in the reverse direction while the armature 19 is attracted to the electromagnet 20, and the projection 6a and the interlocking pin 7a come into contact again, charging the spring 11 of the diaphragm ring 10 and FIG. 2 (a). Return to the initial state shown in. Along with this, the diaphragm plate 30 is also reversed by the elastic force of the spring 31, and the diaphragm blades 32 are opened. Then, when the projecting piece 10d contacts the stop pin 25, the projecting piece 10c operates the aperture opening switch SW1 from the off state to the on state, the motor 1 is stopped, and the viewfinder returns to the observation state. Further, subsequently, the film is wound up and the shutter is charged by a known means (not shown) to return to the next photographing preparation state.

Next, FIG. 6 is an electric circuit for performing programmed automatic exposure control and automatic exposure control with aperture aperture priority or shutter speed priority using the automatic aperture drive device of the embodiment shown in FIGS. 2 is a block diagram of FIG.

In the case of program automatic exposure control: The program mode is selected by the exposure mode setting means 61. Then, the subject brightness information detecting means 51 including the light receiving element 43, the subject brightness information B _V , the film sensitivity information input means 52 to the film sensitivity information S _V , the lens open FNo information input means 53 to the lens open FNo information A.
_VOs are sequentially input to the CPU 50. The CPU 50 uses the preset program to narrow down the number of stages ΔA _V
And the shutter speed _TV is calculated.

Then, after the calculation, the CPU 50 outputs a signal necessary for display to the display means 56. When a motor forward rotation signal is output from the CPU 50 to the motor drive circuit 55 by the release operation, the drive circuit 55 drives the motor 1 to start driving the diaphragm and the mirror. Along with this, a number of pulse signals corresponding to the change of the aperture diameter is input to the CPU 50 from the photo interrupter 14. CPU 50 is the number of narrowing steps ΔA _V
When the number of pulses corresponding to is input, a signal is output to the magnet drive circuit 54, and the release electromagnet 20 performs stop control of the diaphragm. Further, when the mirror-up switch SW2 is turned from off to on due to the completion of mirror-up, the CPU 50
Outputs a stop signal to the motor drive circuit 55, and the motor 1 stops operating. Subsequently, a signal is output from the CPU 50 to the shutter time control means 57 to control the operation of the shutter.

After the trailing curtain travel of the shutter is completed, a motor reverse signal is output from the CPU 50 to the motor drive circuit 55, and the motor 1 is rotated in reverse. Then, when the aperture opening switch SW1 changes from the off state to the on state, the CPU 50 causes the motor drive circuit 55
A stop signal is output to and the motor 1 stops reverse rotation. Then, a signal is output from the CPU 50 to the winding / shutter charge drive control means 58 to wind the film and charge the shutter to complete the photographing.

In case of automatic exposure control with shutter speed priority In this case, the exposure mode setting means 61 selects the shutter speed priority mode. Then, in addition to the input of each information B _V , S _V , A _VO from the brightness information detection means 51, the film sensitivity information input means 52, and the lens open FNo information input means 53 (unnecessary when the aperture size is not displayed). , information _{T V} shutter time which is set from the shutter speed setting means 59 is input to the CPU 50. CPU50
Calculates the number of narrowing steps ΔA _V on the basis of the input information and outputs a signal required for display to the display means 56. After the release operation, the same operation as in the program exposure control is performed.

In the case of automatic exposure control with priority given to the aperture diameter In this case, the exposure mode setting means 61 selects the aperture aperture priority mode. Then, the brightness information detecting means 5
1, film sensitivity information input means 52, lens open FN
O. In addition to the input of each information B _V , S _V , and A _VO from the information input means 53, the set aperture diameter information is sequentially input to the CPU 50 from the aperture diameter setting means 60. The CPU 50 calculates the number of narrowing steps ΔA _V and the shutter time T _V on the basis of the input information, and outputs a signal necessary for display to the display means 56. After the release operation, the operation is similar to the case of the program exposure control.

FIG. 8 shows a case of a conventional diaphragm drive system which operates a diaphragm by a charged spring force described at the beginning of the specification,
FIG. 9 is a characteristic diagram for explaining the diaphragm control accuracy in the case of the diaphragm driving device of the present invention, in which the horizontal axis represents the diaphragm driving time T _O and the vertical axis represents the diaphragm aperture A _V. Further, A _VO shows the aperture open state, and A _VM shows the minimum aperture state.

A curve S is a behavioral characteristic when the diaphragm is driven by a charged spring force in the conventional diaphragm driving method, and the driving speed is delayed by interlocking the governor with the diaphragm driving member in order to improve control accuracy. As can be seen from the curve S, in the conventional diaphragm driving method, the diaphragm driving member continues the acceleration motion, so that there is a large difference in the narrowing speed between when the diaphragm aperture is near the opening and when it is the minimum aperture diameter.
That is, when the control electromagnet operates at A _V1 where the aperture diameter is near the opening, the aperture diameter is determined after a certain operation delay time t peculiar to the electromagnet. That is, what is intended to be stopped at the point c on the curve S is actually controlled to be stopped at the point d, and as a result, the aperture diameter becomes A _V1 ′ and the aperture control error becomes (A _V1 ′ −A _V1). ). Further if the minimum aperture control electromagnet by A _V2 near aperture is activated, actuation delay time t of the electromagnet is that trying to stop at a point e on the curve S is constant is actually stop control at the point f As a result, the aperture diameter becomes A _V2 ′. Therefore, the aperture control error at this time is (A _V2 ′ −A _V2 ), which is considerably larger than the control error near the open position. In order to accurately control both of them, the operating speed of the diaphragm drive member and the control timing of the electromagnet at the aperture to be controlled are calculated, and the control electromagnet must be operated before the target aperture is reached. In fact, it requires a very complicated electric circuit.

On the other hand, the curve M shows the behavior of the diaphragm driving device of the present invention. In the present invention, the aperture ring 10, which is the aperture drive member given the turning tendency in the aperture direction by the spring 11 (see FIG. 1), is initially operated by the holding force by the cogging of the motor 1 in the initial state before the aperture start. Stable in position. Therefore, the diaphragm ring 10 behaves in accordance with the starting characteristics of the motor 1 even when the diaphragm is driven, due to the force relationship. That is, the starting characteristic of the motor 1 does not always perform the accelerating motion, but after accelerating in the initial stage of the starting, it shifts to a substantially constant velocity motion. As a result, the diaphragm ring 10 also moves in the same manner and slightly accelerates near the opening of the diaphragm, but continues to narrow down at a constant speed from the middle.
The curve M shows the behavioral characteristics. Here, for example, when the control electromagnet operates at A _V1 where the aperture diameter is close to the opening, the aperture diameter is determined after a certain operation delay time t of the electromagnet has elapsed. That is, what is stopped at the point g on the curve M is actually controlled to be stopped at the point h, and as a result, the aperture diameter is A
_Therefore , the aperture control error becomes (A _V1 ″ −A _V1 ). Similarly, when the control electromagnet stops operating at A _V2 near the minimum aperture, it shifts from the point i to the point j on the curve M due to the operation delay, and is controlled to A _V2 ″, and the aperture control error is near the opening. The error (A _V2 ″ −A _V2 ) is almost the same. Therefore, in order to accurately control both of them, it is sufficient to operate the electromagnet over the entire aperture diameter, simply considering the operation delay time t of the electromagnet and before reaching the target aperture diameter. Specifically, the photo interrupter 1
By only activating the electromagnet when the output pulse number of 4 is counted by a fixed number less than the target pulse number, almost accurate aperture control is possible in the entire aperture diameter range. This can be achieved with a simple electric circuit, which leads to a significant cost reduction of the camera.

FIG. 9 is an NT characteristic curve of the same motor as that of FIG. 7, wherein the straight line A is the characteristic when the motor is operated using a new dry battery at room temperature, and the straight line B is about −10 ° C. It is the characteristic when the motor using the same battery is operated under the environment.

In the present invention, the diaphragm ring 10 is the spring 3 in the lens.
1 (see FIG. 1), the habit of turning in the narrowing direction is given by the spring 11 which is stronger. Therefore, the load torque exerted on the rotation of the motor 1 at the time of narrowing is a value obtained by subtracting the load torque corresponding to the difference between the spring 31 and the spring 11 from the load torque corresponding to the friction loss of the bearing portion and the meshing portion of the gear train, The value is close to no load. When the motor shaft torque T at this time is T _P , the operating point of the motor at room temperature is point a, and the rotation speed N at that time is N _P close to the no-load rotation speed N ₁ . Next, in a low temperature environment of about −10 ° C., the operating point of the motor is point b, and the rotation speed at that time is N _P ′, which is close to the no-load rotation speed N ₂ . N ₁ and N
_Since the difference between ₂ is small, the difference between N _P and N _P ′ is also a relatively small value. As a result, the narrowing-down time is proportional to the rotation speed of the motor (in other words, the number of rotations per unit time), so it can be said that there is little change in the narrowing-down time due to the operating environment temperature. This means that there is little change in the release time lag due to the operating environment temperature, and it solves the drawbacks of conventional cameras that directly drive the aperture with a motor, allowing fast-moving subjects such as sports photos to be captured by the photographer's intention. Make it easier to shoot in the street.

The same can be said for the deterioration of batteries. This is because as the operating point on the N-T curve of the motor approaches the no-load rotational speed, the amount of change in the operating rotational speed due to the increase in the internal resistance of the battery due to the deterioration of the battery is smaller.

[Effects of the Invention] According to the present invention, since the properties of the motor are most effectively used, the following remarkable effects are obtained.

(I) Since a mechanism for holding the charged state of the spring is not required, it is possible to reduce the size and cost of the camera.

(II) The diaphragm control accuracy can be improved without using a complicated electric circuit.

(III) Since the device has less energy loss, a small battery can be used.

(IV) It is possible to realize a camera with a built-in motor that causes little change in the release time lag due to deterioration of batteries and changes in operating temperature environment.

[Brief description of drawings]

FIG. 1 is a perspective view of an automatic diaphragm driving device for a camera with a built-in motor according to an embodiment of the present invention, and FIGS. 2 (a) to 2 (f) are diaphragm driving stop control shown in FIG. FIGS. 3 (a) to 3 (c) are enlarged front views respectively showing the operation modes of the mechanism, and FIG. 3 (a) to FIG. 3 (c) are a side view, a rear view and an operation mode in which only the mirror drive mechanism is taken out from FIG. 4 (a) and 4 (b) are enlarged cross-sectional views showing magnetically stable points of the built-in motor, and FIG. 5 (a) is a slip clutch attached to the output shaft of the built-in motor. 5 is an enlarged sectional view of FIG. 5, FIG. 5 (b) is a sectional view taken along line bb in FIG. 5 (a), and FIG. 6 is an electric circuit block of a motor built-in camera having the automatic diaphragm driving device. Diagram, FIG. 7 is a characteristic diagram showing a motor rotation speed-torque curve, and FIG. 8 is a throttle aperture and time. Characteristic diagram showing the relationship between, Figure 9, the rotational speed of the motor - is a characteristic diagram showing a torque curve. 1 …… Motor 2,3a, 3b, 4a, 4b, 5,6,7,8,9a, 9b …… Gear (gear train) 10 …… Aperture ring (iris drive member) 11 …… Elastic member 30 …… Narrowing member 80, 81 ...... Stator 82 ...... Armature iron core

Claims (1)

[Claims] 1. A diaphragm driving member that engages with a diaphragm member in a lens barrel, an elastic member that biases the diaphragm driving member in a diaphragm method, a motor having an armature core in a rotor, and a motor. A gear train that connects the diaphragm drive member, and holds the diaphragm drive member at a position where the diaphragm is opened by a holding torque at a magnetically stable point of the motor when the diaphragm is inoperative. The automatic iris driving device for the camera with built-in motor.