JPS623934B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motor-driven lens shutter, and more particularly to a lens shutter in which shutter blades that also serve as aperture blades are driven by a motor.

As is well known, some lens shutters include program shutters in which the shutter blades also serve as aperture blades, and the shutter blades begin to close before they are fully opened. In such a lens shutter, the combination of shutter speed and aperture value is uniquely determined by the brightness of the subject, so its exposure control method is a program exposure control method.

In addition, conventional lens shutters of this type include an everset type that obtains the driving force of the shutter blade by accumulating the pressing force of the shutter release button, and one that obtains the driving force of the shutter blade by the excitation force of an electromagnet. There is. However, the Everset type lens shutter has disadvantages in that the operating stroke of the shutter release rod is long, which tends to cause camera shake and also makes it easy to miss the shutter release. Furthermore, the type of shutter blades in which the driving force of the shutter blades is obtained by the excitation force of the electromagnet has the disadvantage that the operating mechanism is complicated and the manufacturing cost is high.

Furthermore, in both types of lens shutters mentioned above,
Since the aperture curve from the beginning of opening of the shutter blades to the time when the shutter blades are fully opened or half-open is linear, the aperture characteristics are triangular wave characteristics or trapezoidal wave characteristics (see the dotted line in Figure 6). For this reason, there is a limit to increasing the ratio of effective exposure time to total exposure time, and there is a drawback that it is difficult to obtain a high shutter speed. Furthermore, since the exposure time control method is different depending on whether the aperture characteristic is a triangular wave characteristic or a trapezoidal wave characteristic, it is necessary to switch the exposure time control circuit in both cases, which has the disadvantage that the control circuit becomes complicated. be.

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned drawbacks of the conventional art, an object of the present invention is to provide a motor-driven lens in which a cam member is reciprocated by a drive motor that can rotate in forward and reverse directions to open and close shutter blades. To provide the shutter.

According to the present invention, since the shutter blades are opened and closed by a motor, there is no need to charge the shutter prior to releasing the shutter, and a charging mechanism consisting of a return spring, electromagnet, etc. is no longer necessary.
The mechanism becomes extremely simple and failures are reduced.

Furthermore, since the shutter release switch can be operated purely electrically, the mechanism of the shutter release button is simplified, and its pressing stroke can be freely set.

Furthermore, by appropriately selecting the shape of the cam, the aperture curve of the shutter can be made non-linear, and the total exposure time required to give the same amount of exposure to the film surface can be reduced compared to conventional shutters. Can be shortened. Therefore, it becomes possible to obtain a high shutter speed.

Further, if exposure control is performed by directly measuring the light reflected from the film surface, the shape of the shutter aperture curve can be made into any shape.

Furthermore, since the cam hole for fully opening the shutter is provided so as to extend on the same radius as the cam hole when the shutter is fully open, the fully open state of the shutter can be maintained without stopping the motor when the shutter is fully open. Therefore, there is no need to stop the motor even when performing long-time exposure, and the configuration of the exposure time control circuit is simplified.

Also, if the same motor is used to open and close the shutter blades and adjust the distance of the photographic lens, the space occupied by the motor will be reduced.
A compact and lightweight camera can be realized.

Hereinafter, the present invention will be explained based on illustrated embodiments.

As shown in FIGS. 1 and 2, the lens shutter of the present invention is disposed at the front of a camera housing 1, and includes a movable lens group 4 held in a lens barrel 3, and a camera housing 1. A fixed lens 5 attached to the fixed member 2 of the camera, two shutter blades 6a and 6b arranged so as to be openable and closable between the movable lens group 4 and the fixed lens 5, and a rotatable lens attached to the fixed member 2 of the camera. Its main parts are composed of a freely mounted cam ring 7 for distance setting and shutter opening/closing as a cam member, and a drive motor 8 capable of forward and reverse rotation for reciprocating the cam ring 7. .

The cam ring 7 is formed of a donut-shaped disc having an opening 7a for attachment to the immovable member 2 in the center thereof, and as shown in FIG. A sector gear 7b for receiving the driving force to the ring 7 is carved in the portion extending over the ring 7. A transmission gear 9 is meshed with this sector gear 7b, and this transmission gear 9 transmits rotational force from the output shaft 8a of the drive motor 8 via a rotating shaft 11, a worm wheel 12, and a worm 13. It is becoming more and more common. Therefore, as the motor 8 rotates forward and backward, the cam ring 7
is designed to rotate back and forth. Further, a cam hole 15 for distance setting and shutter opening/closing is bored in the annular plate portion of the cam ring 7.
A shutter opening/closing drive pin 14 as a driving member for opening/closing the shutter blades 6a, 6b is fitted into the shaft 5.

As shown in FIG. 3, the cam hole 15 is a distance setting cam hole formed in a partial arc shape on the same radius near the opening 7a so as to correspond to the closed state of the shutter blades 6a, 6b. Part 15a (signs α and β
) and the shutter blades 6a, 6
cam hole portion 15b (portion between symbols β and γ) for preparing to open the shutter for changing the shutter blade from the closed state to the state immediately before opening, the shutter blade 6a,
The shutter opening cam hole 15c (the part between symbols γ and δ) for changing the shutter blade 6b from the opening start state to the fully open state, and the cam ring 7 so as to correspond to the fully open state of the shutter blades 6a and 6b. Shutter fully opening cam holes 15d (portions between δ and ε), which are formed in a partial arc shape on the same radius near the peripheral edge, are successively formed.

The shutter blades 6a, 6b are formed of a well-known vario-type shutter and are disposed at a rear position of the cam ring 7. That is, both shutter blades 6a, 6b have their bases connected to support shafts 16a, 1.
6b, and are rotatably supported by elongated holes 17a and 17 bored at their bases.
The drive pin 14 is fitted into b. Thereby, the shutter blades 6a, 6b are opened and closed by moving the drive pin 14 in the direction indicated by arrow a.

The lens barrel 3 also includes the cam ring 7.
It is placed at the front position of the camera so that it can be rotated and moved back and forth. That is, the lens frame 3 is rotated by screwing together a male helicoid gear 3a carved on the outer peripheral surface of the rear small-diameter cylindrical portion with a female helicoid gear 2a carved on the stationary member 2. It is designed to move back and forth. Further, the large-diameter cylindrical portion at the front of the lens frame 3 is slidably fitted into a part of the camera housing 1. A flange portion 18 is provided in a protruding manner at the boundary between the small-diameter cylindrical portion at the rear and the large-diameter cylindrical portion at the front. This collar portion 18 has a ratchet portion 1 for distance setting on a part of its outer peripheral surface.
8a and a stepped portion 18 for transmitting driving force to the lens frame 3
b are formed respectively. The stepped portion 18b
A distance setting drive pin 19 embedded in the cam ring 7 is engaged with the cam ring 7, and when the cam ring 7 rotates counterclockwise, the lens frame 3 is rotated by the pin 19. , so that it is extended forward. In addition, the ratchet portion 18a
The row of teeth is formed to correspond to the set number and set position of the zone focus that can set the distance in the camera, and the lower end claw of the claw member 21 is provided in the same part 18a for stopping the lens frame 3. The portion 21a extends so that it can be engaged. This claw member 21
The upper left extending arm of the plate formed in an inverted H shape is bent rearward to form a release piece 21b, and the base of the upper right arm is swingably supported on a support shaft 22. There is. The claw member 21 is given the habit of always rotating counterclockwise by a compressible coil spring 23 whose one end is engaged with the free end of the upper right arm. This behavior is regulated by the engagement of the lower claw portion 21a with the ratchet portion 18a. In addition, the above-mentioned support shaft 2
2, an inverted L-shaped release lever 24 is swingably supported. The left extending arm of the release lever 24 extends below the release piece 21b of the claw member 21, and when the lever 24 swings clockwise, it pushes and moves the release piece 21b to release the claw member 21. The member 21 is swung counterclockwise against the elasticity of the coil spring 23, and the claw portion 21a and the ratchet portion 18 are
It is designed to remove the multiplication of a. One end of a compressible coil spring 25 is engaged with the tip of the hanging arm of the release lever 24, and constantly biases the lever 24 to swing clockwise. The elasticity of this spring 25 is selected to be weaker than the elasticity of the spring 23.
The claw member 21 is not swung only by the elasticity of the claw member 21. However, since the release pin 26 with an extended tip is mounted on the cam ring 7 so as to be able to engage with the hanging arm of the release lever 24,
When the cam ring 7 rotates from the position where the pin 26 is to the right of the hanging arm 24, the pin 26 comes into contact with the hanging arm of the lever 24, pushes the release lever 24, and forcibly releases the claw member 21. Rock the claw part 2
The engagement between the ratchet portion 1a and the ratchet portion 18a can be released. Note that one end of a compressible coil spring 28 is engaged with a pin 27 implanted in the flange 18 of the lens frame 3, and the lens frame 3 is always urged to rotate clockwise. ing. Then,
When the engagement between the claw portion 21a and the ratchet portion 18a is released, the lens frame 3 automatically moves back to the position where the camera is most retracted.

On the other hand, a movable contact piece 31 made of an F-shaped electrically conductive plate spring member is fixed to a part of the outer peripheral edge of the cam ring 7. This movable contact piece 31 has
A pair of contacts are provided, including a common terminal 33 formed on the substrate 32 and rotation angle detection terminals 34a to 34a.
34d, respectively.
These common terminals 33 and rotation angle detection terminals 34a to 34d are connected to a control circuit 35 formed of an integrated circuit or the like, which controls a series of operations such as shooting distance setting operation and shutter release operation of the camera. each connected. This control circuit 35 includes distance setting pushbutton switches 3 corresponding to distances of infinity, 3 m, 1.5 m, and 0.8 m, respectively.
6a to 36d are connected to each other. Also,
A push button switch 37 for shutter release is also connected.

The rotation angle detection terminals 34a to 34d are sequentially formed counterclockwise, and their formation positions correspond to the formation positions of the respective teeth of the ratchet portion 18a. In addition, the rotation angle detection terminal 3
4a to 34d are the distance setting push button switches 3
6a to 36d, respectively. and,
The control circuit 35 controls the extended position of the lens barrel 3, that is, the amount of rotation of the cam ring 7 by controlling the movable contact piece 31.
Detection is performed by electrical connection between one of the rotation angle detection terminals 34a to 34d and the common terminal 33. Further, when this detected position matches the photographing distance selected by pressing any one of the push button switches 36a to 36d, the circuit 35 reverses the drive motor 8 through a drive circuit (not shown). There is. It goes without saying that the rotation of the motor 8 is started by pressing the shutter release push button switch 37 via the control circuit 35.

Further, the control circuit 35 is connected to a photometric light receiving element 39 for directly measuring the reflected light of the subject light L on the surface of the film 38. This photometric light receiving element 39 is connected to the shutter blades 6a, 6.
When the lens b is opened, the reflected light of the subject light L incident on the film surface is received through the movable lens group 4, the shutter aperture, and the fixed lens 5, and the exposure amount of the film 38 becomes approximately half of the proper exposure amount. At this point, the motor 8 is reversed through the control circuit 35, which serves to control the amount of exposure to the film 38.

As described above, the motor-driven lens shutter of the present invention is constructed.

Next, the operation of this lens shutter will be explained.

First, the photographer determines the distance to the subject by visual measurement, and presses one of the zone focus distance setting push buttons 36a to 36d corresponding to this distance. Then, this distance information is transmitted to the control circuit 3.
5 and stored in the same circuit. Next, when the shutter release push button switch 37 is pressed down, the drive motor 8 is rotated through the control circuit 35, and the cam ring 7 begins to rotate counterclockwise from its original position in the stopped state shown in FIG. 4A. However, if the push button switch 36a corresponding to the infinite distance is pressed down, the rotation angle detection terminal 34a and the common terminal 33 are already connected in the original position shown in FIG. 4A, and the lens frame Since the cam ring 3 is positioned so as to form an image of the subject at infinity on the film surface, the cam ring 7 is not rotated counterclockwise.

If the push button switch 36 corresponding to the distance 0.8m
If d is pressed down, the cam ring 7 rotates from the position shown in FIG. 4A to the position shown in FIG. 4B. During this rotation, the cam ring 7 rotates the lens frame 3 together in the counterclockwise direction via the drive pin 19 and the stepped portion 18b. Then, mirror frame 3
has a helicoid gear 3a on the fixed member 2 of the camera,
2a, the lens group 4 is rotated from the original position shown in FIG. 5A to extend the lens group 4.
Furthermore, when the lens frame 3 is rotated, as shown in FIG. 5B, since the claw member 21 is biased by the spring 23, the claw portion 21a successively passes over the teeth of the ratchet portion 18a. , engages the rightmost tooth corresponding to a distance of 0.8 m. When the cam ring 7 rotates to the position shown in FIG. 4B, the rotation angle detection terminal 34d and the common terminal 33 corresponding to a distance of 0.8 m
The control circuit 35 compares this with the stored distance information based on the depression of the push button switch 36d, detects a match, and reverses the motor 8. Then, the cam ring 7 begins to rotate clockwise, moving from the position shown in Figure 4B to the fourth position.
Return to the original position shown in Figure A. During this comeback,
The lens frame 3 is prevented from moving back because the claw portion 21a of the claw member 21 engages with the rightmost teeth of the ratchet portion 18a, and is held at the extended position shown in FIG. 5B. . Therefore, drive pin 1
9 disengages from the engagement with the stepped portion 18b and moves back to the original position. Note that this cam ring 7 rotates from the original position shown in FIG. 4A to the position shown in FIG. 4B,
In the process of adjusting the distance of the photographing lens, which returns to the original position shown in FIG. Therefore, the shutter blades 6a and 6b do not move during this period, and the shutter blades 6a and 6b do not operate in the closed state.

Since the drive motor 8 continues to rotate, the cam ring 7, which has returned to the original position shown in FIG. 4A, is further rotated clockwise from this original position. Then, the shutter blades 6a, 6b
The drive pin 14 goes beyond the β position of the cam hole 15 and enters the shutter opening preparation cam hole 15b. Therefore, the drive pin 14 gradually begins to move toward the outer diameter of the cam ring 7 in the direction indicated by arrow a in FIG. Then, the shutter blades 6a and 6b gradually start moving in a direction in which the blade portions move away from each other. And the drive pin 14
When the shutter blades 6a and 6b reach the γ position of the cam hole 15, the shutter blades 6a and 6b begin to open.

Further, the release pin 26 further moves clockwise from the position shown in FIG. 5A, and once the release lever 2
4 and swings counterclockwise against the elasticity of the spring 25 to move to the right position of the lever 24, as shown in FIG. 5C. In addition, pin 2
After the lever 6 moves to the right position of the lever 24, the lever 24 is moved back to the original position by the elasticity of the spring 25.

When the shutter blades 6a and 6b begin to open, the subject light L enters the film surface through the movable lens group 4, the shutter aperture, and the fixed lens 5.
The light receiving element 39 receives the reflected light from the film surface and starts integrating the amount of exposure to the film 38. As the cam ring 7 rotates, the drive pin 1
4 is the cam hole 15 for opening the shutter.
Since it moves in c from the γ position to the δ position,
The drive pin 14 further moves in the outer radial direction, and the shutter blades 6a, 6b are gradually opened more widely as shown in FIG. 4C. If drive pin 14
Assuming that the amount of exposure to the film 38 measured by the light-receiving element 39 becomes approximately half of the proper exposure amount at position A while the camera is moving inside the cam hole 15c, at this point Then, the control circuit 35 reverses the driving motor 8. Therefore, the cam ring 7 starts rotating clockwise again, and the drive pin 1
4 moves back from the A position toward the γ position. Then, when the cam ring 7 rotates until the drive pin 14 comes to the γ position, the shutter blades 6a and 6b are closed again. In this way, before the drive pin 14 reaches the δ position of the cam hole 15, which corresponds to the fully open state of the shutter blades 6a and 6b, the amount of exposure to the film 38 reaches approximately half of the appropriate amount of exposure, and the motor is activated. 8 is reversed, the aperture characteristic of the shutter is given the symbol γ-A- in FIG.
It becomes a curve connecting t ₁ . In this case, since there is no difference in the number of rotations per unit time of the motor 8 depending on whether the motor 8 rotates in forward or reverse directions, the opening characteristics of the shutter become symmetrical. Therefore, unless there is a large change in the subject brightness during the opening of the shutter blades 6a, 6b, the film 38 will be exposed to twice the proper exposure amount, ie, twice the proper exposure amount.

Further, even if the drive pin 14 passes through the shutter opening cam hole 15c and reaches the δ position, the film 38
If the exposure amount to is less than half of the appropriate exposure amount, the cam ring 7 further rotates clockwise.
As shown in FIG. 4D, the drive pin 14 moves the shutter fully opening cam hole 15d from the δ position to the ε position. Since the cam holes 15d are formed on the same radius corresponding to the fully open state of the shutter blades 6a and 6b, the drive pin 14 does not move in the radial direction after passing through the δ position. The opening diameter of the shutter is the maximum shutter opening O.
Maintain the fully open state at the diameter of . Therefore, the drive pin 14
When the shutter moves within the cam hole 15d, the opening area of the shutter remains constant, and its opening characteristics are as follows.
In the figure, it is a straight line connecting symbol δ-B. Then, at position B while the drive pin 14 is moving within the cam hole 15d, the amount of exposure to the film 38 measured by the light receiving element 39 becomes approximately half of the appropriate amount of exposure. , the control circuit 35 outputs an inversion signal for the drive motor 8, and the motor 8 is inverted. As a result, the cam ring 7 rotates clockwise again, and the drive pin 14 fully opens the shutter blades 6a, 6b to the δ position, and gradually opens the shutter blades 6a, 6b from the δ position to the γ position. While closing, it moves back to the γ position. Drive pin 1
4 reaches the γ position, the shutter blades 6a, 6b
is completely closed, and the exposure of the film surface is completed. As described above, when the drive pin 14 is in the shutter fully opening cam hole 15d and the amount of exposure to the film 38 reaches approximately half of the appropriate amount of exposure, the opening characteristics of the shutter are as follows. The curve connecting the sign γ-δ and the straight line connecting the sign δ-B are B
The curve is symmetrical around the point. Therefore,
As long as there is no large change in the brightness of the subject while the shutter blades 6a, 6b are open, the film 38 will be irradiated with an appropriate amount of light.

Even if the cam ring 7 is rotated, the drive pin 14 is moved back to the γ position, and the shutter blades 6a, 6b are closed, the drive motor 8 continues to rotate, so the cam ring 7 is not rotated further. Ru. This rotation of the cam ring 7 causes the release pin 26 mounted on the ring to come into contact with the release lever 24, forcing the lever 24 to swing counterclockwise as shown in FIG. 5D. Then, since the left extending arm of the release lever 24 is engaged with the release piece 21b of the claw member 21, the claw member 21 is swung clockwise against the elasticity of the spring 23, and the claw part 21a and the claw member 21 are swung clockwise. The engagement with the ratchet portion 18a is released. When this relationship is broken,
The lens barrel 3 is rotated clockwise by the spring 28 and returned to the original position shown in FIG. 5A, in which the camera is retracted the most. Note that the release pin 26 climbs over the release lever 24 and
After returning to the original position, which is the left position of
Engages with the leftmost tooth of. Also, as the cam ring 7 rotates, the movable contact piece 31 fixed to the cam ring 7
move back together, electrically connecting the rotation angle detection terminal 34a corresponding to the infinite distance and the common terminal 33 again. Then, the control circuit 35 detects this,
A stop signal for the motor 8 is output, and the rotation of the motor 8 is immediately stopped. At the time when the motor 8 stops, the drive pin 14 has reached the β position in the cam hole 15, so it stops at this position, and the shutter blades 6a and 6b stand still in a completely closed state. Further, the drive pin 19 moves back again to the position corresponding to the step portion 18b and stops. Therefore, the lens shutter returns to the initial state shown in FIG. 2 and stops its operation.

Furthermore, when the shutter release push button switch 37 is pressed again after one frame of film 38 has been taken, the distance adjustment of the photographing lens and the release of the shutter are performed in the same manner as described above. Of course, the photographing is performed sequentially and the photographing is performed again.

In the above embodiment, the distance is set by selectively pressing the plurality of pushbutton switches 36a to 36d, but the means for setting the distance may be, for example, a rotary switch. Of course, this may be done using a switch or the like. Additionally, an automatic focus detection device may be installed to detect the in-focus state in conjunction with the extension of the photographic lens, and to set the distance by reversing the motor using a signal at the time of in-focus. Of course.

In addition, the drive motor 8 was reversed when the shutter was opened when the amount of exposure to the film 38 became approximately half of the appropriate amount of exposure, but taking into consideration the inertia of the motor 8, etc. do,
Needless to say, it may be reversed just before it is halved.

Furthermore, since there is a certain limit to the length of the cam hole 15d for fully opening the shutter, if an extremely long exposure is required, the motor 8 is stopped when the drive pin 14 reaches the ε position. Count the time difference between the time when the amount of exposure light reaches half of the appropriate exposure amount, and after this time has elapsed from the time when the amount of exposure light reaches half of the appropriate amount of exposure, rotate the motor 8 in the opposite direction to the previous rotation direction. You can do it like this.

Further, the return movement of the lens barrel 3 is performed in conjunction with the return movement of the cam ring 7 to its original position.
Of course, the backward movement of the lens frame 3 may be performed in conjunction with the winding of the film 38.

According to the lens shutter of this embodiment, as shown in FIG. 6, by appropriately selecting the shape of the cam hole 15, the aperture characteristic of the shutter can be made non-linear. When the total exposure time is given by a short time t ₁ compared to the time t ₂ or t ₄ in a conventional shutter shown by the dotted line,
Or just _t3 . Therefore, a faster shutter speed can be obtained.

As described above, according to the present invention, it is possible to provide a motor-driven lens shutter that eliminates the drawbacks of the conventional lens shutter mentioned at the beginning of the specification and is extremely convenient in terms of use and manufacture. .

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a motor-driven lens shutter showing an embodiment of the present invention, FIG. 2 is an exploded perspective view of the main parts of the lens shutter shown in FIG. 1, and FIG. , a front view showing the cam ring of the lens shutter shown in FIG. 1 above, and FIGS. 4A to D
5A to 5D are front views showing the operating states of the cam ring 7 shown in FIG. 3 above, and FIGS. 5A to 5D are front views showing the operating states of the lens barrel of the lens shutter shown in FIG. 1 above, respectively. , FIG. 6 is a shutter aperture characteristic diagram of the lens shutter shown in FIG. 1 above. 3...Lens barrel, 6a, 6b...Shutter blades, 7...Cam ring, 8...Drive motor, 14...-Shutter opening/closing drive pin, 15...
...Cam hole, 15a... Extension cam part (cam hole part for distance setting), 15b... First circumferential cam part (shutter opening preparation cam hole part), 15c... Inclined cam part (cam hole part for distance setting ), 15d... second circumferential cam portion (cam hole for fully opening the shutter), 19... connecting member (drive pin).

Claims (1)

[Scope of Claims] 1. A shutter blade that exposes a film surface by opening and closing operations, a drive pin for opening and closing the shutter that opens and closes the shutter blades, a lens barrel that moves forward and backward in the optical axis direction by rotation, and A drive motor that can rotate in reverse; a cam ring that has a cam groove into which the drive pin is fitted; and a connecting member that makes partial contact with the lens barrel, and that is rotated back and forth by the drive motor. , a first circumferential cam part that holds the shutter in the fully closed position in the cam groove, an inclined cam part that opens and closes the shutter, a second circumferential cam part that holds the shutter in the fully open position, and the connecting member. A motor-driven lens shutter characterized by being formed by an extension cam part connected to a first circumferential cam part that allows the cam ring to rotate to the extent that it contacts and rotates the lens barrel.