JP4346167B2 - Camera shutter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a camera shutter, usually referred to as a lens shutter, that opens and closes a circular exposure opening by reciprocating operation of a shutter blade.
[0002]
[Prior art]
Recent cameras are becoming more and more motorized, and in the case of lens shutters, the number of shutter blades that are opened and closed by a motor has increased. In addition to the stepping motor, the motor used in that case is a current-controlled motor in which the rotation direction of the permanent magnet rotor is determined by the direction of current application and can rotate only within a predetermined angle range. Is used. The current control motor is often referred to as a moving magnet type motor in the industry. Although it is inferior in terms of driving force compared to a stepping motor, the control system is simple, low cost and small size. There is a feature that it is suitable for the transformation. The present invention relates to a device that opens and closes shutter blades with such a current-controlled motor, and various proposals have been made for the configuration of this type of motor, and a typical one is as follows. This is described in Japanese Utility Model Publication No. 6-24815 and Japanese Patent Application Laid-Open No. 11-98800.
[0003]
In addition, since this type of motor does not have a large driving force as described above, variations in the manufacturing stage of components such as permanent magnet rotors and shutter blades, and variations in the assembly stage may cause the opening / closing operation characteristics of the shutter blades. It is easy to have a great influence. Therefore, in such a case, as described in the above Japanese Utility Model Publication No. 6-24815, an adjustment circuit is provided in the control system of each shutter, and the motor drive circuit is provided during assembly adjustment. By adjusting the supplied current and voltage, the opening operation time (rise time) until the shutter blades fully open the exposure opening from the pinhole can be approximated to the design standard (individual difference adjustment). Are known.
[0004]
By the way, in the case of a shutter that opens and closes a shutter blade by such a current control motor, the closed state of the shutter blade when the camera is not used is normally maintained by the magnetic force of the permanent magnet of the rotor. Yes. That is, even when the motor is in a non-energized state, the attractive force of the permanent magnet rotor causes the rotor to rotate in the direction opposite to the shutter blade opening operation direction between the rotor and the stator. It is made to act, it is made into the state blocked | prevented by the predetermined | prescribed stopper, and it is trying to maintain a closed state.
[0005]
Therefore, when photographing, if the stator coil is energized in the forward direction and the shutter blade is opened, the opening operation is performed against the above suction force, and then the energization is performed in the opposite direction. When the shutter blade is closed, the closing operation is performed by applying the above suction force. Accordingly, the shutter blade is closed faster than the opening operation, and the opening / closing operation characteristic of the shutter blade is the magnitude of the suction force when the closed state is maintained. Will be heavily dependent on. Therefore, conventionally, even when such suction force varies at the time of production, the current supplied to the motor drive circuit as described in the above Japanese Utility Model Publication No. 6-24815 Individual differences were adjusted by adjusting the voltage and obtaining a predetermined rise time.
[0006]
[Problems to be solved by the invention]
However, on the basis of the variation in the suction force for maintaining the closed state, the individual difference of the rise time is adjusted as described above, and control such as starting the closing operation of the shutter blades before fully opening or flashing is performed. On the contrary, if the synchronization control or the like can be appropriately performed, there is a problem that a large variation is caused with respect to the closing operation time (fall time) of the exposure aperture. This will be described in detail with reference to FIG.
[0007]
FIG. 3 shows the opening / closing operation characteristics of the shutter blades. The solid line (x) indicates a case where the predetermined opening / closing operation characteristics are obtained at a predetermined voltage (eg, 1.3 V) according to the design standard. Is shown. In that case, as described above, the closing operation is earlier than the opening operation. Also, if the suction force acting in the shutter closed state is weaker than the design standard due to production variations (individual differences), even if the applied voltage is the same, the dot-dash line As shown by, the opening operation is earlier and the closing operation is slower than in the case of the design standard. On the contrary, when the suction force acting in the shutter closed state is stronger than in the case of the design standard, the opening operation is slower than in the case of the design standard as shown by the broken line of Δ, but the closing operation is performed. Will be faster. Therefore, the variation width of the fall time in this case is the A time shown in FIG.
[0008]
Therefore, by individual difference adjustment, a voltage (for example, 1.2 V) lower than the reference voltage (1.3 V) is applied in the case of the dot-and-dash line with a circle, and the reference voltage in the case of a broken line with a triangle It is assumed that a rise time similar to that of the solid line can be obtained by applying a voltage (for example, 1.4 V) higher than (1.3 V). However, when such an adjustment is made, even if the rise time approximates to the design standard, the variation in the fall time has increased.
[0009]
That is, in the case of the one-dot chain line, the attractive force in the closing direction due to the magnetic force of the permanent magnet is originally small and the applied voltage is made lower than the reference voltage. As indicated by the mark, the fall time becomes extremely long, and in the case of the broken line, the attractive force in the closing direction due to the magnetic force of the permanent magnet was originally high and higher than the reference voltage. The falling time is further shortened as indicated by Δ-1 than the case of Δ, and the variation width is longer than the A time and becomes B time. .
[0010]
In the above description, while the voltage adjustment value is the same 0.1 V, in FIG. 3, the fluctuation of the falling time in the case of the broken line is smaller than the fluctuation of the falling time of the one-dot chain line. Needless to say, this is set so that the fall time in the case of the design standard is as short as possible while taking into account the load of the shutter blades (the same applies to the rise time), and Thus, this type of motor cannot be said to have a very good driving force, so even if the same adjustment is made on the side where the applied voltage is increased and the side where the applied voltage is decreased, the fall time of the design standard is not exceeded. This is because the adjustment effect hardly appears in the direction of shortening the time.
[0011]
The present invention has been made to solve such problems, and the object of the present invention is to provide a variation in the fall time even if the rise time variation of the shutter blades is electrically adjusted during manufacture. It is an object of the present invention to provide a current-controlled motor-driven camera shutter that does not need to be increased.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a shutter for a camera according to the present invention includes a predetermined number of shutter blades that open and close an exposure opening by a reciprocating operation, and a permanent magnet rotor that rotates by a predetermined angle range in a different direction depending on the energization direction. A motor that opens and closes the shutter blades, detection means for detecting a plurality of operating positions of the shutter blades for measuring the opening speed of the shutter blades, and when the shutter blades are opened. A motor drive circuit that supplies currents in different directions to the motor during the closing operation, an exposure control circuit that outputs a close signal at a timing corresponding to the exposure conditions, and a predetermined voltage applied to the motor drive circuit. A constant voltage circuit to be obtained and applied to the motor drive circuit from the constant voltage circuit based on a detection result of the detection means at the time of manufacturing the shutter A voltage regulator circuit that adjust in the lower voltage range than the voltage of the constant voltage circuit of pressure, the at the time of opening operation of the shutter blade by applying a voltage adjusted by the voltage adjusting circuit to the motor drive circuit wherein the exposure control A voltage selection circuit for directly applying a voltage higher than the voltage adjusted by the voltage adjustment circuit from the constant voltage circuit to the motor drive circuit when receiving a closing signal from the circuit is provided.
In the camera shutter according to the present invention, it is preferable that an initial position detection signal of the shutter blade by the detection means is a control start signal of the exposure control circuit.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the illustrated examples. First, the configuration of this embodiment will be described with reference to FIG. The shutter base plate 1 has an opening 1a for restricting the exposure opening at the center thereof, and forms a blade chamber with an auxiliary base plate (not shown) arranged on the back side thereof. The auxiliary base plate also has a planar shape similar to that of the shutter base plate 1, and has an opening having the same shape as the opening 1a at a position overlapping the opening 1a. Further, the shutter base plate 1 is formed with a long hole 1b penetrating to the blade chamber and a window portion 1c. In the blade chamber, two shafts 1d and 1e and two stoppers 1f and 1g are provided. .
[0014]
Two shutter blades 2 and 3 are arranged in the blade chamber. Among them, the shutter blade 2 is rotatably attached to the shaft 1d and has a long hole 2a, a detected portion 2b, and a tip portion 2c. The other shutter blade 3 is rotatably attached to the shaft 1e, and has a long hole 3a, a detected portion 3b, and a tip portion 3c.
[0015]
On the surface side of the shutter base plate 1 (the subject side when incorporated in the camera), a photodetector and a current control motor are attached. However, since all of these configurations are well-known, the drawings are schematically shown so as not to complicate the drawings and allow only the basic configuration to be understood. First, the photodetector of the present embodiment is a photo reflector 4, and the light emitting portion 4a and the light receiving portion 4b face the long hole 1b. And the light radiate | emitted from the light emission part 4a is reflected in a blade chamber, and the reflected light is light-received by the light-receiving part 4b.
[0016]
The motor of this embodiment has a permanent magnet rotor 5 magnetized in two poles, a stator coil 6, and a magnetic member 7 attached to the stator. A drive pin 5 a is provided at a position protruding from the radial direction 5. The drive pin 5 a is inserted into the blade chamber from the window portion 1 c and is fitted into the long holes 2 a and 3 a of the shutter blades 2 and 3. Depending on the rotation direction of the rotor 5, the shutter blade 5 a 2 and 3 are made to perform an opening operation or a closing operation.
[0017]
Further, the motor control system includes a power supply 8, a constant voltage circuit 9, a voltage adjustment circuit 10, a voltage selection circuit 11, a motor drive circuit 12, an exposure control circuit 13, and an information processing circuit 14. The voltage selection circuit 11 can be connected to the motor drive circuit 12 directly with the constant voltage circuit 9 or via the voltage adjustment circuit 10. As a matter of course, the voltage applied to the motor drive circuit 12 is lower when the connection is made via the voltage adjustment circuit 10 than when the constant voltage circuit 9 is directly connected.
[0018]
Next, the operation of this embodiment will be described with reference to the timing chart of FIG. FIG. 1 shows a closed state of the shutter. At this time, the coil 6 is not energized. However, the rotor 5 is given a force that rotates counterclockwise by the magnetic force of the permanent magnet. This is because the attractive force is exerted by the magnetic force of the permanent magnet so that the central portion around the S pole of the rotor 5 is located on the line connecting the rotation shaft of the rotor 5 and the magnetic member 7.
[0019]
The counterclockwise rotational force is transmitted to the shutter blades 2 and 3 via the drive pin 5a, and the shutter blade 2 is rotated counterclockwise on the shaft 1d, and the shutter blade 3 is rotated clockwise on the shaft 1e. However, since the tip portions 2c and 3c of the shutter blades 2 and 3 are in contact with the stoppers 1f and 1g, this closed state is maintained. In order to prevent counterclockwise rotation applied to the rotor 5, the drive pin 5a may be brought into contact with the upper edge of the window portion 1c.
[0020]
Prior to shooting, when a power switch (not shown) is closed, the exposure control circuit 13 controls the control time (usually exposure time, electrical time, etc.) based on information such as subject brightness and film sensitivity. (Although this is not the case), various warning circuits and the like are activated. At this time, since the photoreflector 4 is also energized, the light emitted from the light emitting portion 4a is reflected by the reflecting means in the blade chamber, and the reflected light enters the light receiving portion 4b. In FIG. 2, such an incident state is referred to as “light transmission” for convenience, and a non-incident state is referred to as “light shielding”. Note that the above control time can be changed in accordance with the change in subject brightness during shooting.
[0021]
Next, when the shutter is released, an automatic focusing device (not shown) operates to focus, and when this is finished, a shutter blade opening operation start signal is given from the information processing circuit 14 to the motor drive circuit 12. . At that time, since the voltage selection circuit 11 connects the motor drive circuit 12 to the constant voltage circuit 9 via the voltage adjustment circuit 10, the motor drive circuit 12 uses the voltage set in the constant voltage circuit 9. Therefore, a current corresponding to the adjusted voltage is supplied to the coil 6 in the forward direction. Thereby, the rotor 5 is rotated in the clockwise direction, and the shutter blades 2 and 3 are opened by the drive pin 5a. Note that the arrows between the circuits in FIG. 1 indicate the information transmission direction.
[0022]
When the shutter blades 2 and 3 start to open, the detected portion 2b of the shutter blade 2 blocks the optical path of the photoreflector 4 until the opening 1a is in the pinhole state. Therefore, the exposure control circuit 13 starts counting the exposure time by a signal from the information processing circuit 14 based on the detection signal for starting the interruption. Thereafter, when a substantially pinhole state is reached, the detected portion 2b of the shutter blade 2 releases the light shielding state of the photoreflector 4, opens the opening 1a, and then the detected portion 3b of the shutter blade 3 Immediately before the optical path of the reflector 4 is blocked and the opening 1a is fully opened, the light shielding state is solved. The opening operation of the shutter blades 2 and 3 performed in this way is stopped after the drive pin 5a abuts against the lower edge of the window 1c after the opening 1a is fully opened. Thus, even if it will be in such a stop state, electricity supply with respect to the coil 6 is continuing.
[0023]
Next, when the exposure time count by the exposure control circuit 13 ends, the end signal is given to the voltage selection circuit 11, the voltage of the constant voltage circuit 9 is directly applied to the motor drive circuit 12, and The coil 6 is energized in the reverse direction from the motor drive circuit 12. Therefore, the rotor 5 is rotated counterclockwise more rapidly than in the opening operation, and the shutter blades 2 and 3 are operated by the drive pin 5a to close the opening 1a. Immediately after closing the opening 1a, the shutter blades 2 and 3 are stopped by the tip portions 2c and 3c coming into contact with the stoppers 1f and 1g, so that the photo reflector 4 by the detected portion 2b of the shutter blade 2 is stopped. After the elapse of a predetermined time from the release of the light shielding state, the coil 6 is deenergized and the state shown in FIG. 1 is obtained. In this embodiment, the voltage selection circuit 11 is already in the selection state of the voltage adjustment circuit 10 in the state of FIG. 1, but this state is the shutter blade opening operation start signal. It goes without saying that it may be selected by the above.
[0024]
Therefore, next, FIG. 3 is used in addition to FIGS. 1 and 2, and how to adjust the individual difference of the rise time at the time of production of this embodiment, and how the problem of the present invention is solved in this embodiment. Whether this is done will be described so that it can be easily compared with the conventional adjustment method described above. First, in the case of the present embodiment, the set voltage of the constant voltage circuit 9 is 1.5V. In addition, as in the case of the above-described conventional example, the design-standard opening / closing operation characteristics are as indicated by the solid line shown in FIG. 3 when a voltage of 1.3 V is applied to the motor drive circuit 12. It has been established. In order to measure the actual rise time, a special measuring instrument must be prepared. Therefore, in the present embodiment, the measurement object of the rise time is the photo reflector 4 by the detected portion 2b of the shutter blade 2. The time from the end of the light blocking state to the end of the light blocking state of the photoreflector 4 by the detected portion 3b of the shutter blade 3, and the design reference time is t (see FIG. 2).
[0025]
Therefore, at the time of manufacture, a voltage of 1.3 V is applied to the motor drive circuit 12 of each shutter via the voltage adjustment circuit 10, and the rise time defined as described above is measured. When the measured value is shorter than the rise time t of the design standard, the voltage applied through the voltage adjustment circuit 10 is set lower than 1.3V, and when the measured value is longer than 1.3V, Thus, the same rise time t as the design standard is obtained.
[0026]
By the way, when the measured rise time is shorter than the case of the design standard as shown by the one-dot chain line shown in FIG. 3, the voltage applied to the motor drive circuit 12 is adjusted to 1.2 V by the voltage adjustment circuit 10. In addition, as indicated by the broken line, when the voltage is longer than the design standard, the voltage applied to the motor drive circuit 12 is adjusted to 1.4 V so that the rise time t of the design standard can be obtained. The point is exactly the same as the conventional case described above. However, as described above, if such adjustment is performed, even if the rise time variation can be eliminated, the fall time variation width becomes large as indicated by B in FIG.
[0027]
Therefore, in this embodiment, in the closing operation, a voltage of 1.5 V is directly applied from the constant voltage circuit 9 to the motor drive circuit 12. Then, in the case of the one-dot chain line, it becomes 0.3 V higher than the applied voltage during the opening operation, and in the case of the broken line, it becomes 0.1 V higher. And since there is a difference in the voltage value to be added between them, and the shorter the fall time is, the shorter the amount of time for a certain positive voltage value is, the less As shown in FIG. 3, the closing operation characteristic of the dot-dash line is indicated by ◯ -2, and the broken line is indicated by △ -2. Therefore, the one shown with a dashed line is much shorter than the case where the fall time is -1 and the one shown with a broken line is slightly shorter than the case where -1 is given. In addition to being small, it is smaller than A before adjusting the rise time.
[0028]
【The invention's effect】
As described above, according to the present invention, the shutter blade is opened and closed by reciprocating rotation of a current-controlled motor having a permanent magnet rotor, and the magnetic attractive force acting between the rotor and the stator is closed. In the motor-driven camera shutter that is maintained using the above, when the opening operation is performed, a voltage adjusted at the time of manufacture is applied to the motor driving circuit, and when the closing operation is performed, Since a voltage higher than the adjusted voltage is applied from the constant voltage circuit, the variation in the fall time can be suppressed even if the rise time variation of the shutter is electrically adjusted. have.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an embodiment.
FIG. 2 is a timing chart for explaining the operation of the embodiment.
FIG. 3 is an opening / closing operation characteristic diagram for explaining variation in falling time of shutter blades in the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Shutter base plate 1a Opening part 1b, 2a, 3a Long hole 1c Window part 1d, 1e Shaft 1f, 1g Stopper 2, 3 Shutter blade 2b, 3b Detected part 2c, 3c Tip part 4 Photo reflector 4a Light emission part 4b Light reception part 5 Rotor 5a Drive pin 6 Coil 7 Magnetic member 8 Power source 9 Constant voltage circuit 10 Voltage adjustment circuit 11 Voltage selection circuit 12 Motor drive circuit 13 Exposure control circuit 14 Information processing circuit

Claims (2)

A motor having a predetermined number of shutter blades that open and close the exposure opening by a reciprocating operation, a permanent magnet rotor that rotates by a predetermined angle range in a different direction depending on the energization direction, and the shutter blades performing an opening and closing operation; Detection means for detecting a plurality of operating positions of the shutter blades for measuring the opening speed of the shutter blades, and supplying currents in different directions to the motor when the shutter blades are opened and closed. A motor drive circuit; an exposure control circuit that outputs a closing signal at a timing corresponding to an exposure condition; a constant voltage circuit that can apply a predetermined voltage to the motor drive circuit; and a detection result of the detection means during manufacture of the shutter electrostatic adjusted within a lower voltage range than the voltage of the voltage the constant voltage circuit which is applied from the constant-voltage circuit to the motor drive circuit on the basis of the An adjustment circuit and a voltage adjusted by the voltage adjustment circuit at the time of opening the shutter blade are applied to the motor drive circuit, and when a closing signal is received from the exposure control circuit, the constant voltage circuit to the motor drive circuit And a voltage selection circuit for directly applying a voltage higher than the voltage adjusted by the voltage adjustment circuit . 2. The camera shutter according to claim 1, wherein an initial position detection signal of the shutter blade by the detecting means is a control start signal of the exposure control circuit.

Images