JPH05249538A - Electromagnetic-driven diaphragm device - Google Patents

Abstract

PURPOSE:To obtain the high accuracy of diaphragm diameter by adding one step or subtracting one step to/from total driving amount when a discriminated result by a discrimination means is an odd step number and stopping final energizing at a target diaphragm position by one-phase energizing. CONSTITUTION:By a microcomputer 211 in a zoom lens 200, it is discriminated whether the total driving step number (diaphragm step driving amount) is an even number or an odd number. In the case of the even number, the final energizing at the target diaphragm position is stopped by the one-phase energizing. Besides, when it is discriminated to be the odd number, one step is added to the total driving step number or subtracted from it by the computer 211 in the lens 200 and the final energizing at the target diaphragm position is stopped by the one-phase energizing. In such a case, a step motor 216 is driven by as much as optional amount by a diaphragm driving circuit 210 by deciding in which direction out of coils 214 and 215 the energizing is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetically driven diaphragm device for mounting on an optical device such as a camera, and more particularly to an electromagnetically driven diaphragm device which uses a stepping motor as a power source for driving the diaphragm.

[0002]

2. Description of the Related Art In recent years, an exposure amount adjusting device, which functions as a shutter device and a diaphragm device in a non-lens interchangeable type camera generally referred to as a compact camera, has mainly used a stepping motor as a driving power source. On the other hand, also in diaphragm devices for interchangeable lenses of single-lens reflex cameras, electromagnetically driven diaphragm devices using a stepping motor as a power source have been put to practical use.

The electromagnetic drive diaphragm device to be mounted on the interchangeable lens of a single-lens reflex camera is mainly developed by the applicant of the present invention.
No. 04, No. 59-26808, No. 6
JP-A-62-240942 and JP-A-62-240942, which are electromagnetic drive diaphragm devices having an arcuate stepping motor as disclosed in Japanese Unexamined Patent Publication No. 0-140934 and improved motors of these electromagnetic drive diaphragm devices. JP-A-1-
An electromagnetically driven diaphragm device having a similarly arcuate stepping motor disclosed in Japanese Patent No. 164258 is known.

Further, the applicant of the present invention has disclosed the above-mentioned Japanese Patent Laid-Open No. 62-
As an improvement of the electromagnetically driven diaphragm device disclosed in JP-A-240942 and JP-A-1-164258, an electromagnetically driven diaphragm device driven by a stepping motor disclosed in Japanese Patent Application No. 2-27730 is proposed. is doing.

Incidentally, the stepping motor for driving the diaphragm blades disclosed in the above-mentioned Japanese Patent Laid-Open No. 62-240942 has the following structure.

That is, while a rotor shaft to which a rotor magnet is fixed is rotatably supported by a bearing, a pinion gear is coupled to the tip of the rotor shaft, and the other end of the rotor shaft is rotatably supported by a fan-shaped bearing plate to rotate the rotor magnet. Support freely,
The outer periphery of the rotor magnet is divided and alternately magnetized, and is anisotropically oriented. Each stator includes several fork-shaped pole teeth, and the pole teeth are alternately arranged so as not to contact each other.

On the other hand, the stepping motor of the electromagnetically driven diaphragm device disclosed in the above-mentioned Japanese Patent Application No. 2-27730 has the following structure.

That is, the rotor having eight poles on its outer peripheral surface and having a groove at the center of the magnetization, and the first and second magnetic pole portions having an opening angle of about 90 ° in electrical angle are substantially U-shaped. The first and second stators, which are wound around the armature coil, are provided at the tip ends of the first and second extension portions that are separated by an electrical angle of approximately 180 °. At (90 + 180 ×
m) ° (m = 0, 1, ...) Spaced apart.

[0009]

The above-mentioned electromagnetically driven diaphragm device of the prior art described above has various problems to be further improved mainly in the structure and function of the motor and the diaphragm blade control operation.

In the exposure amount adjusting apparatus using the conventional stepping motor as a driving power source (for example, in the case of a single-lens reflex camera), how many steps the rotor is rotated after the stepping motor is energized from a predetermined phase. The aperture size is determined by the setting.

Therefore, in order to obtain a highly accurate aperture diameter, it is desirable that the angle at which the rotor rotates per step is small.

On the other hand, in order to avoid exhaustion of the battery serving as a power source, it is desirable that the rate of de-energizing the motor is high when exposure is performed for a relatively long time. For that reason, the cogging torque causes the rotor to stably stop. It is desirable that there are many stopping positions for each rotation of the rotor.

However, the above-mentioned Japanese Utility Model Laid-Open No. 59-2680.
No. 4 publication, No. 59-26808 publication and No. 6 development.
In the conventional example disclosed in Japanese Patent Publication No. 0-140934,
The number of pulses required for one rotation of the rotor when the well-known 1- and 2-phase energization is performed is 16 pulses, whereas there are only four stable stop positions due to the cogging torque, which is equal to the number of magnetized poles. Even when performing exposure for a long time, in order to obtain a high aperture diameter accuracy, it is necessary to continue energizing the coil, and there is a problem that the battery serving as a power source is exhausted.

Further, in the electromagnetically driven exposure amount adjusting device disclosed in JP-A-62-240942 and JP-A-1-164258, since the stator is arranged three-dimensionally, the phase of each magnetic pole is changed. However, it is difficult to dispose them accurately, and it is difficult to stably obtain a high aperture diameter accuracy.

Further, in the electromagnetically driven exposure amount adjusting device disclosed in Japanese Patent Laid-Open No. 1-164258, the cogging torque of the rotor when the power is cut off relative to the number of positions where the rotor can be stopped when the power is continued. The number of positions that can be stably stopped by is 1/2, which is relatively large,
If the power is turned off at a stop position where it becomes unstable when the power is turned off, it is not possible to determine whether it is deviated by one step in the direction of the small throttle or one step in the opening direction due to the cogging torque, resulting in an error of ± 1 step. Therefore, the exposure does not change, or the exposure changes to 1/2 step, for example, when a 1/4 step automatic exposure shift shooting is performed in the so-called auto bracket mode. There was a drawback that the result would be contrary. Further, even in the continuous shooting mode in which the aperture value is constant, there is a drawback that each exposure results in a change of 1/2 step.

Further, in the above-mentioned conventional example, if the stator length and the rotor length are shortened in order to reduce the height of the driving unit in order to make the lens barrel compact, the performance of the camera in the vicinity of the forbidden voltage is significantly deteriorated. was there. In particular, after failing to follow the electric pulse and stepping out or narrowing down,
There was a drawback that it could not be held in that state and accurate caliber accuracy could not be obtained. On the other hand, JP-A-62-24
In the motor of the electromagnetically driven diaphragm device disclosed in Japanese Patent No. 0942, each stator is provided with several fork-shaped pole teeth, and a pair of stators intricately arranged from above and below so that the respective pole teeth do not contact each other. However, in this motor, even if the rotor is biased to the stator to suppress the vibration of the rotor, the rotor is located at a position where the force exerted by the stator in the vertical direction of the rotor is balanced. When the rotor vibration occurs, it cannot be rapidly attenuated because the rotor is likely to vibrate due to the action of the external force and the rotor attracting force does not act in a certain direction. Further, in the motor of the electromagnetically driven diaphragm device disclosed in Japanese Patent Application No. 2-27730, the rotor is magnetized to 8 poles, but the 6 pole rotor could not be adopted in the motor of this device. If a 6-pole rotor is adopted, the angular velocity per step of the rotor will be 1.3 times more than that of an 8-pole rotor, the moment of inertia of the rotor itself will increase, and as a result damping of the diaphragm blades will increase and control will become difficult. ,
This is because, as in the case of the above-mentioned conventional example, accurate caliber accuracy cannot be obtained. However, in order to enable further downsizing of the motor, a rotor with 6 poles is preferable to 8 poles, and therefore, this electromagnetically driven diaphragm device needs to be improved for further miniaturization.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electromagnetically driven diaphragm device which solves the above-mentioned problems or drawbacks of the prior art and can obtain a high diaphragm aperture accuracy.

[0018]

SUMMARY OF THE INVENTION The present invention, in an electromagnetically driven diaphragm device having a 1-2 phase energization type stepping motor, corresponds to the diaphragm drive amount based on the photometric value, the focal length of the photographing optical system, and the open F number. The motor drive control means is provided with a discrimination means for discriminating whether the total drive amount of the sum of the drive amount of the drive throttle of the motor is an even number of steps or an odd number of steps. By making the total drive amount +1 step or the total drive amount -1 step, the final energization at the target diaphragm position is stopped by the one-phase energization.

The electromagnetically driven diaphragm device according to the present invention is
A plurality of light-shielding blades, a cam member having a cam that restricts the movement of the light-shielding blades, an opening / closing means for opening and closing the light-shielding blades,
A stepping motor for driving the opening / closing means, and the stepping motor comprises a rotor and first and second substantially U-shaped stators arranged on the outer circumference of the rotor. A pole is magnetized, and a groove is formed on the outer peripheral portion thereof at a position deviated from the center of the magnetization by a predetermined angle in a predetermined clockwise or counterclockwise direction. The first and second stators are respectively formed. It has substantially U-shaped first and second extension portions, and the first and second magnetic poles having an opening angle of 90 ° in electrical angle are approximately 180 ° in electrical angle at the tips of these extension portions. An armature coil is wound around the first extension portion and is provided separately from the first extension portion and the second extension portion.
Of the stator has an electrical angle of {90 + 180 × m} ° (m =
0, 1, 2, 3, ...) Spaced from each other, and the rotor is configured so that a propulsive force acts on the first and second stators in a certain direction. ..

[0020]

FIG. 2 is a schematic diagram showing a zoom lens equipped with an electromagnetically driven diaphragm device according to the present invention and a camera body equipped with the zoom lens.

In FIG. 2, reference numeral 100 denotes a camera body, 20
Reference numeral 0 is a zoom lens detachably attached to the camera body 100, and 103 is a photometric circuit. A shutter driving circuit 104 is connected to the focal plane shutter 106 and the microcomputer 105. 107 is a battery that controls the operation of the camera system, 108a is a group of contact pins on the camera body 100 side, and 108b is a zoom lens 20.
0 side contact pin group. The pin group 108b is arranged so as to face the contact pin group 108a on the camera body 100 side when the lens 200 and the camera body 100 are completely mounted. 209 is a step motor 2 for driving the diaphragm
16 is an electromagnetic drive diaphragm device, and the diaphragm drive circuit 21
0 and the microcomputer 211 in the lens. Reference numeral 212 is a zoom brush for detecting the focal length of the photographing lens, and 213 is an aperture open detection switch.

Next, the operation of each part of the zoom lens and camera body will be described with reference to the flowchart of FIG. In FIG. 1, in step # 2, each microcomputer, counter, etc. are reset. In step # 3, first, the amount of light measured by the photometry circuit 103 of the camera is calculated in a known manner in consideration of factors such as film sensitivity, shutter speed, and aperture value to determine the number of aperture steps. This is performed by the microcomputer 105 in step # 4, and an aperture drive command is sent to the microcomputer 211 in the zoom lens. The microcomputer 211 in the zoom lens which has received the diaphragm drive command converts the number of diaphragm stages instructed from the camera side microcomputer 105 into a step motor drive step in step # 5. Further, in step # 6, the zoom lens 2 is moved by the zoom brush 212.
The focal length of 00 is detected, and the running diaphragm drive amount that matches the focal length and the open F number is calculated. This is the step #
It is performed at 7, # 8 and # 9.

Next, the microcomputer 211 in the zoom lens discriminates whether the total number of driving steps (number of diaphragm steps + running diaphragm driving amount) is an even number or an odd number. This determination is made in step # 10, and when the number of steps is even, the final energization at the target diaphragm position is 1
Since the stop is caused by the phase energization, that is, the stable position where the stepping motor is stopped even when the energization to the stepping motor is stopped,
At 0, the step motor 216 is driven by an arbitrary amount by determining in which direction the coil 214 or the coil 215 is energized. This is done in step # 12.

On the contrary, when it is determined in step # 10 that the total number of driving steps (number of diaphragm steps + driving amount of running diaphragm) is an odd number of steps, the final energization at the target diaphragm position is two-phase energization. Since the motor is stopped, it is not possible to determine whether the stepping motor is deenergized by one step in the direction of the small aperture or one step in the opening direction due to the cogging torque.
1 (total number of driving steps + 1 step)
Or, by setting (total driving step number-1 step), final energization at the target diaphragm position is stopped by one-phase energization.

This is performed in step # 11, and the diaphragm drive is performed in step # 12 (total driving step number + 1 step).

FIG. 3 is a diagram showing the relationship between the stop position of the 1-2 phase energization type stepping motor 216 and the aperture diameter.

In FIG. 3, a is a position where the stepping motor can be stopped without energization, that is, a one-phase energized position, b is a position where two coils are simultaneously energized and stopped, and c is a position.
Is the diameter of the lathe in the electromagnetically driven diaphragm (fixed opening diameter in the diaphragm) near the telephoto of the zoom lens, e is the mechanical stopper position where the stepping motor cannot rotate further, and d is the stepping motor In mechanical standby position. h is the drive amount of the approaching diaphragm in the vicinity of the telephoto, and f and g are the positions where the open diameter is determined in a part of the lens barrel near the middle and wide, respectively.
Also, the drive amount of the approaching diaphragm at this time is the amount shown by i and j,
This amount is detected by the zoom brush 212 in FIG.

Further, the diaphragm drive amount (the number of diaphragm steps) based on the photometry result is the diaphragm drive amount based on c, f, and g in the vicinity of the tele, in the vicinity of the middle, and in the vicinity of the wide, respectively. The sum of the detected drive amount of the approaching diaphragm is the number of driving steps of the stepping motor 216 in each zoom range, and the microcomputer 211 in the photographing lens determines whether the number of driving steps is an even number or an odd number.

For example, in the vicinity of the middle, when the diaphragm is moved to the position of l, the number of driving steps up to l is an odd number, and the position of l is an unstable position which cannot be stopped when the power is turned off. At this time, if there is a one-step deviation toward the small aperture side due to the cogging torque, the same aperture accuracy as at the position of m will be obtained. Similarly, when the diaphragm is moved to the position of n, the position of n is also the position of the two-phase energization, so if the position shifts to the open side by one step, the aperture accuracy becomes the same as the position of m.

In this embodiment, the distance between a and b is set to 1
Since it is equivalent to / 8 steps, the theoretical result is that the amount of change of 1/4 steps does not change when the aperture accuracy at the position of l and the position of n is checked.

On the contrary, if the position of 1 shifts to the position of k and the position of n shifts to the position of o due to the cogging torque, the theoretical change amount of 1/4 step is 1/2 step as the actual change amount. Becomes

In the present embodiment, when the control to the two-phase energization position occurs, the diaphragm drive is performed by +1 step (or -1 step), and when the two-phase energization positions are seen, it is always 1 /. It is possible to obtain four stages of variation even when the stepping motor is de-energized.

Next, referring to FIGS. 4 to 8, the second embodiment of the present invention will be described.
Examples will be described.

In these figures, 1 is a cam member, 2 is a light-shielding blade, 3 is a rotating ring, 4 is a rotor, 5 is a fixed ring, 6 is a first stator, 7 is a second stator, and 8 is a first stator. , 9 is a second armature coil, 10 is a bearing member, and 11 is a flexible printed circuit board. When the rotor 4 of the stepping motor rotates, the gear of the rotor meshes with the gear of the rotating ring 3 which is the opening / closing means, so that the rotating ring 3 rotates and the light shielding blade 2 is driven by a predetermined amount.

Each of these members will be described in detail below.

In FIG. 4, a cam member 1 made of, for example, plastic is provided with cam grooves 1a, 1b, 1c, 1d and 1e equal in number to a plurality of light-shielding blades and convex portions 1f, 1g, 1h and 1i. Is provided, the convex portion 1f,
The inner peripheral portion of 1g, 1h, and 1i with respect to the optical axis Z is fitted to the outer diameter portion 3a of the rotating ring 3 to rotatably support the rotating ring 3. Further, holes are provided in each of the convex portions 1f, 1g, 1h, 1i, and screws 13a, 13 are passed through the holes.
The cam member 1 is fixed to the fixing ring 5 by fixing b, 13c and 13d (13b to 13d are not shown) to the screw holes 5a, 5b, 5c and 5d provided in the fixing ring.

The light-shielding blades 2 made of plastic, for example, are used in the same number as the number of cams provided on the cam member, but only one is shown in FIG. 4 and the others are omitted.

The first dowel 2a provided on the light-shielding blade 2 is fitted in the first cam groove 1a provided on the cam member 1, and the second dowel 2b is provided on the rotating ring 3. It fits similarly to the hole 3b of No.1.

Similarly, the first and second dowels of the second to fifth light shielding blades (not shown) are also fitted in the cam grooves formed in the cam member 1 and the holes formed in the rotary ring 3.

Convex portions 1f, 1g, 1h, 1i of the cam member 1
Has a height that is larger than the sum of the thickness of the rotating ring 3 and the thickness of the light-shielding blade by a predetermined amount, and with the cam member 1 and the fixed ring 5 incorporating the rotating ring 3 and the light-shielding blade 2. When the rotating ring 3 is fixed by the screws 13a to 13d, the rotating ring 3 is regulated in the position in the optical axis direction while having a certain backlash. A gear 3h is provided on a part of the outer peripheral portion of the rotating ring 3. Then, this gear meshes with the gear of the rotor described later.

The cam member 1 is provided with a bearing hole 1j, and the first shaft portion 4d of the rotor 4 is pivotally supported.

For example, the fixing ring 5 integrally formed of plastic is provided with a first pedestal portion 5e, a second pedestal portion 5r, and a third pedestal portion 5h.
The first pedestal portion 5e is provided with a first positioning pin 5f for positioning the first stator 6 and a first groove 5g having a step. Similarly, the second pedestal portion 5
In r, the second stator 7 for positioning the second stator 7 is positioned.
The positioning pin 5p and the second groove 5q having a step are provided.

The third pedestal portion 5h is provided with a hole 5j which is larger than the outer diameter of the rotor 4 by a predetermined amount, and the first extension portion 5i for positioning the first stator 6 is provided.
And a second extension portion 5m for positioning the second stator 7 is provided. Further, the third pedestal portion 5h has third, fourth and fifth grooves 5k, 5 having steps.
1, 5n (fifth groove 5n is not shown) are provided.

The first stator 6 is made by laminating silicon steel plates, for example, and has a substantially U-shape as shown in FIG. The first and second extension portions 6b, 6 of the first stator 6
The first and second magnetic pole portions 6 that face the outer peripheral portion of the rotor 4 via a predetermined gap are provided at the tip portions of d.
The first and second magnetic pole portions 6a and 6c of the first stator 6 provided with a and 6c have an electrical angle of about 90 °, respectively.
And an electrical angle of 180 ° from each other.

A first armature coil 8 is fitted on the first extension portion 6b of the first stator 6.

In the first armature coil 8, a copper wire 8b is wound around a bobbin 8a made of plastic, and both ends (that is, winding start and winding end) of the terminals 8c and 8d pressed into the bobbin. ) Is electrically connected by means such as soldering. Further, the first stator 6
Is provided with a positioning hole 6e.

Similarly, the second stator 7 is also made by laminating silicon copper plates, for example, and has a substantially U-shape as shown in FIG. First and second extension portions 7b of the second stator 7
The first and second magnetic pole portions 7a and 7c are provided at the tips of the rotors 7d and 7d, respectively, which face the outer peripheral portion of the rotor 4 with a predetermined gap. The first of the second stator 7
And the second magnetic pole portions 7a and 7c each have an electrical angle of about 90 degrees.
They have an open angle of 180 ° and are separated from each other by 180 ° in electrical angle.

The armature coil 9 is fitted to the first extension portion 7b of the second stator 7.

In the second armature coil 9, a copper wire 9b is wound around a bobbin 9a made of plastic, and both ends (that is, winding start and winding end) of the terminals 9c and 9d pressed into the bobbin. ) Is electrically connected by means such as soldering. In addition, the second stator 7
Is provided with a positioning hole 7e.

When the first stator 6 is assembled to the fixed ring 5, the first stator 6 is brought into contact with the first and third convex portions 5e and 5h of the fixed ring 5 to perform positioning in the optical axis direction, and thus the first stator 6 is formed. 6 and the first positioning pin 5f provided on the fixed ring 5 are fitted together, and as shown in FIG. 5, the first extension portion 6b and the second extension portion 6b of the first stator 6 are joined together. By fitting the first extension portion 5i of the fixing ring 5 into the gap 6d, the positioning in the direction perpendicular to the optical axis is performed.

Like the first stator 6, the second stator 7 is attached to the fixed ring 5 by abutting the second and third convex portions 5r and 5h of the fixed ring 5 on the optical axis. Directional positioning is performed and the holes 7 of the second stator 7 are
e and the second positioning pin 5 provided on the fixing ring 5.
p is fitted, and as shown in FIG. 5, the second extending portion 5m of the fixing ring 5 is fitted in the gap between the first extending portion 7b and the second extending portion 7d of the second stator 7. By matching, the positioning in the direction perpendicular to the optical axis is performed.

The rotor 4 is made of a plastic magnet, and the first and second rotating shafts 4d and 4e, the gear 4c, and the magnetic pole portion 4a are integrally molded. The magnetic pole portion 4a of the rotor 4 has polar anisotropy so that uniform magnetic poles of 6 poles can be formed on the outer peripheral portion, and similarly, the magnetic pole portion 4a is magnetized so that uniform magnetic poles of 6 poles can be formed. There is.

Further, each of the magnetic poles 4a of the rotor 4 has N
A groove 4b is provided on the outer circumference at a position displaced by a predetermined angle in the clockwise direction or the counterclockwise direction from the center of the pole and the S pole. A first rotation shaft 4d of the rotor 4 is rotatably supported by a first bearing hole 1j provided in the cam member 1. On the other hand, the second rotating shaft 4e of the rotor 4 is rotatably supported by the second bearing 10a provided on the bearing member 10.

The bearing member 10 is made, for example, by integral molding of plastic, and has a bearing 10a that supports the second rotating shaft 4e of the rotor 4 and first to fourth holes 10l and 10l.
m, 10n, 10r. First to fourth holes 10l,
The terminals 8c, 8d, 9c and 9d of the above-mentioned first and second armature coils 8 and 9 are guided to the back surface of the bearing member 10 through 10m, 10n and 10r, and are connected to the flexible printed board 11. The flexible printed board is connected to a drive circuit (not shown).

The bearing member 10 includes the first to fourth protrusions 1
0b, 10d, 10f, 10i are provided (the second protrusion 10d is not shown), and the first to fifth portions are provided on the respective protrusions.
Hooks 10c, 10e, 10g, 10h, and 10j (the second hook 10e is not shown) are provided. These first to fifth hooks 10c, 10e, 10g, 10
h and 10j are first to first provided on the fixed ring 5, respectively.
The bearing member 10 is engaged by engaging with the grooves 5g, 5q, 5k, 5l having the fifth step and the hook being locked at the step.
Are fixed to the fixing ring 5.

At this time, the positioning of the bearing member 10 in the direction perpendicular to the optical axis direction is performed by the first positioning pin 5f of the fixing ring 5, the first positioning hole 10p of the bearing member 10 and the second positioning of the fixing ring 5. Pin 5p and bearing member 10
The second positioning holes 10q are fitted into each other.

Therefore, the cam member 1 and the fixed ring 5 are fixed by the screws 13a ... With the rotating ring 3 interposed therebetween, and the fixed ring 5 and the bearing member 10 position the stators 6, 7 and the rotor 4. Then, the first to fifth hooks 10c, 10e, ... Of the bearing member 10 are fitted into the grooves 5g, 5q ,. When the rotor 4 rotates, its gear 4c meshes with the gear 3h of the rotating ring 3, so that the rotating ring 3
Rotate in a predetermined direction, and the light-shielding blades 2 rotate about the dowels 2a, so that the light amount is appropriately reduced.

Next, referring to FIG. 5, the phase relationship between the first and second magnetic pole portions 6a and 6c of the first stator 6 and the first and second magnetic pole portions 7a and 7c of the second stator 7 will be described. Will be described. As described above, the magnetic pole portions 6a, 6c,
7a and 7c have an opening angle of 90 ° in electrical angle, and the magnetic pole portion 6a and the second magnetic pole portion 6c of the first stator 6 are separated from each other by 180 ° in electrical angle. The first magnetic pole portion 7a and the second magnetic pole portion 7c of the second stator 7 are also separated from each other by an electrical angle of 180 °.

Further, the first magnetic pole portion 6 of the first stator 6
a and the second magnetic pole portion 7c of the second stator 7 are separated from each other by an electrical angle of 630 °, which is equivalent to a phase difference of 90 ° between the first stator 6 and the second stator 7. According to a command from a microcomputer mounted on the camera, a well-known two-phase stepping motor driving method such as one-phase excitation, two-phase excitation, or one-two-phase excitation is used.
The diaphragm device can be driven to a predetermined diaphragm value or returned to the open position.

The six grooves 4b, which are provided on the magnetic pole surface of the rotor 4 and have the same number of magnetic poles, have a central direction P in the clockwise direction or the counterclockwise direction with respect to the central direction O of the magnetization. It is provided at a position shifted by Q °.

Next, the relationship with the torque when the rotor length and the stator length are shortened will be described below with reference to FIGS.

As is well known, FIG. 6 shows T- in which the vertical axis represents the axial torque of the stepping motor and the horizontal axis represents the frequency.
It is f curve, and shows the relationship before and after shortening the rotor length and the stator length in the conventional example.

CA is PULLOUT (escape torque) before shortening the rotor length and stator length, CB is PULLIN (retracting torque) before shortening the rotor length and stator length, and KA and KB are rotor length and stator, respectively. PULLOUT and PULLIN after shortening the length.

As described above, as apparent from FIG. 6,
When the rotor length and the stator length are shortened, the axial torque of the stepping motor naturally decreases.

FIG. 7 is a diagram schematically showing the movement of the diaphragm blades when the axial torque of the stepping motor is reduced.

In the same figure, the vertical axis represents the amount of light on the image plane that changes as the diaphragm blade narrows, the horizontal axis represents time, and the figure shows the damping state immediately before the diaphragm blade stops after being driven. In FIG. 7, when the axial torque of the stepping motor is reduced, the originally desired amount of light on the image plane is represented by the solid line LA, and the load torque (load inertia) of the diaphragm portion at LC point exceeds the axial torque of the stepping motor. In the end, the amount of light on the image plane of LB that is darker than the amount of light on the image plane of LA is displayed.

In the present invention, the rotor of the conventional example shown in FIG. 9 (enlarged front view of the stepping motor portion) is divided into 8 poles, and the rotor shown in FIG. The shaft torque can be increased by increasing the facing area of 20a in FIG. 9 to 6a in FIG. The generated shaft torque T is expressed by the following relational expression.

T = k.hm = k.h'm '(h>h') where T ... axial torque of stepping motor, k ... amount of magnetic flux per unit area of rotor, h and h '... height of stator , M and m ′ ... Circumferential length of the stator. That is, the axial torque is proportional to the cross-sectional area of the stator facing the rotor, and according to the configuration of the present embodiment, even if the rotor length and the stator length are shortened, driving is performed without reducing the axial torque of the conventional stepping motor. The parts can be made compact.

As described above, the increase in the angular velocity due to the hexapole of the rotor adversely affects the accuracy of the aperture diameter. Specifically, as shown in FIG. 7, the damping cycle (dt) of the aperture blades and Increasing the amplitude (dθ) longer than before has a bad effect.

That is, the adverse effect of the increase in the angular velocity of the rotor is equivalent to the phenomenon when the axial torque is reduced. In this embodiment, as shown in FIG. 8, the first and second stators 6 and 7 are not affected. By arranging the rotors 4 in a staggered manner like t1 and t2, a propulsive force is exerted in a certain direction A, and the transmission efficiency with the gear 3h provided on the rotating ring 3 is maximized to solve the problem. There is.

This is because the gear 3 provided on the rotating ring 3 is suppressed by suppressing the vibration of the rotating rotor 4 in the optical axis direction.
It is intended to prevent loss due to frictional force with h, maximize transmission efficiency, and efficiently transmit both the detent torque and the holding torque of the rotor 4 itself to the rotating ring 3.

The propulsive force B is applied to the rotor 4 in one direction B.
The effect is the same even if it is configured to work.

[0073]

As described above, according to the electromagnetically driven diaphragm device of the first embodiment of the present invention, a high diaphragm precision can be obtained without exhausting the battery even during long-time exposure, and particularly, so-called auto bracket mode and the like. With this, there is an effect that an exposure that always changes by 1/4 step can be obtained even if automatic exposure shooting of 1/4 step is performed.

Further, even in the continuous shooting mode in which the aperture value is constant, there is an effect that a high aperture precision without exposure fluctuation can be obtained.

Further, in the electromagnetically driven diaphragm device according to the second embodiment of the present invention, the rotor is divided into six poles to increase the facing area of the stator and the rotor exerts a propulsive force in one direction on the stator. With this configuration, the electromagnetic exposure amount adjusting device can be made compact without reducing the axial torque of the stepping motor, and further, the interchangeable lens can be made compact.

Further, in the magnetization of the rotor, conventionally, there was a great variation in the surface magnetic flux, and depending on the variation, there was no choice but to provide a step of demagnetizing and then re-magnetizing. Due to the polarization, the pitch per pole becomes longer, and variations in the surface magnetic flux are suppressed, and the effect of re-magnetization can be eliminated.

Further, since the rotor is constituted so that the propulsive force acts on the stator in one direction, not only the transmission efficiency is improved, but also the transmission efficiency is improved. Since the vibration of the rotor itself is reduced, the operating noise of the electromagnetic exposure amount adjusting device is also reduced.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining the function and operation of an electromagnetically driven diaphragm device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of the electrical configurations of a zoom lens and a single-lens reflex camera body that incorporate an electromagnetically driven diaphragm device having the function shown in FIG.

FIG. 3 is a diagram showing a relationship between a stop position of a stepping motor of the electromagnetically driven diaphragm device and a diaphragm aperture.

FIG. 4 is an exploded perspective view of an electromagnetically driven diaphragm device according to a second embodiment of the present invention.

5 is a view of the stepping motor of the apparatus shown in FIG. 4 viewed from the axial direction.

FIG. 6 is a Tf diagram showing the relationship between torque and frequency of a stepping motor.

FIG. 7 is a diagram showing damping of diaphragm blades in the diaphragm device.

8 is an enlarged vertical sectional view of a part of the stepping motor shown in FIG.

FIG. 9 is a view of a conventional stepping motor as viewed from the axial direction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cam member 2 ... Light-shielding blade 3 ... Rotating ring (opening / closing means) 4 ... Rotor 4b ... Grooves 6, 7 ... Stator 6a, 6c, 7a, 7c ... Magnetic poles 6b, 6d, 7
b, 7d ... extension part 8, 9 ... armature coil 100 ... camera body 200 ... zoom lens 103 ... photometric circuit 105 ... microcomputer 106 ... focal plane shutter 107 ... battery 108a, 108
b ... Contact group 209 ... Electromagnetic drive diaphragm device 210 ... Diaphragm driving circuit 211 ... Microcomputer 212 ... Zoom brush 213 ... Diaphragm open detection switch 214, 215 ... (Stepping motor) coil 216 ... Stepping motor

Claims (2)

[Claims] 1. A plurality of shading blades, an opening / closing means for opening / closing the shading blades, a 1-2 phase energization type stepping motor for driving the opening / closing means, and a motor drive for controlling energization of the stepping motor. An electromagnetically driven diaphragm device having a control means, for calculating a diaphragm drive amount corresponding to a photometric value based on a photometric result, and an auxiliary diaphragm drive amount of a stepping motor corresponding to a focal length and an open F number of a photographing optical system. And a discriminating means for discriminating whether the total driving amount is an even number of steps or an odd number of steps, by calculating the total driving amount of the sum of the diaphragm driving amount based on the photometric value and the auxiliary aperture driving amount. And a correction means for adding +1 step or -1 step to the total drive amount when the result of the determination by the determining means is an odd number of steps, and the motor drive control means is provided with the target aperture position. An electromagnetically driven diaphragm device, characterized in that the stepping motor is controlled so that the final energization of the apparatus can be stopped by one-phase energization. 2. An annular rotating member having a plurality of light-shielding blades and having an optical path hole at the center thereof which is opened and closed by the light-shielding blades, and the rotating member arranged outside the optical path hole. The stepping motor includes a rotation driving stepping motor and a gear mechanism that transmits the output rotation of the stepping motor to the rotating member. The stepping motor includes a rotor and first and second stators arranged around the rotor. The electromagnetically driven diaphragm device is characterized in that the rotor is configured such that a propulsive force acts on the first and second stators in a certain direction.