JP2683131B2 - Exposure control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure amount adjusting device for adjusting an exposure amount by using a stepping motor used in a still camera, a video camera or the like as a driving power source, and particularly to a driving device. The present invention relates to a stepping motor which is a power source.

[Conventional technology]

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-interchangeable lens type camera generally called a compact camera, is mainly one in which a stepping motor is used as a driving power source. On the other hand, in a diaphragm device in an interchangeable lens of a single-lens reflex camera, a stepping motor is also used as a power source for driving.

As an electromagnetically driven exposure amount adjusting device using such a stepping motor as a driving power source, Japanese Patent Application No. 61-179139 (Japanese Utility Model No. 63-84128) and Japanese Patent Application No. 61-194283 (Japanese Utility Model No. 63-98526), Japanese Utility Model Sho 61-197212 (Japanese Utility Model Sho 63-10)
1924), Japanese Patent Application No. 61-309396 (Japanese Patent Application Laid-Open No. 63-163438), etc., and an arcuate substrate, and a rotor having four poles magnetized on its outer periphery. There is known an electromagnetically driven exposure amount adjusting device which uses a stepping motor as a driving power source, which comprises a pair of substantially U-shaped stators and a pair of coils for exciting the respective stators.

In addition, as shown in Japanese Utility Model Publication No. 62-240942, etc.
A coil wound around an iron core parallel to each rotor axis, and a plurality of magnetic pole portions that are erected on a surface perpendicular to the rotor axis and that face the outer peripheral surface of the rotor. An exposure amount adjusting apparatus using a stepping motor having a pair of stators as a driving power source is also known.

[Problems to be solved by the invention]

By the way, in the exposure amount adjusting device using the stepping motor as a drive power source, for example, in the case of a single-lens reflex camera, energization of the stepping motor is started from a predetermined phase to rotate the step rotor. The aperture diameter is determined depending on 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 to turn off the power to the motor when performing exposure for a relatively long time. For that purpose, the cogging torque causes the rotor to rotate magnetically per revolution of the rotor. It is desirable that there are many stable stopping positions. However, in the above-mentioned conventional example, the number of pulses required for one rotation of the rotor when performing well-known 1 and 2 phase energization is 16
In contrast to the pulse, there are only four stable stop positions due to the cogging torque, which is equal to the number of magnetic poles. Therefore, even when performing exposure for a relatively long time, in order to obtain a high aperture aperture accuracy, There has been a problem that the power supply of the battery, which is a power source, is great because the coil must be continuously energized and thrown.

Further, in the electromagnetically driven exposure amount adjusting device disclosed in Japanese Utility Model Laid-Open No. 62-240942, since the stator has a three-dimensional arrangement, it is difficult to accurately arrange the phases of the magnetic poles. There is a problem that it is difficult to stably obtain a high precision of the aperture diameter.

[Means for solving the problem]

The present invention relates to an exposure amount adjusting device having a plurality of light-shielding blades and a stepping motor for driving the plurality of light-shielding blades, wherein the stepping motor has 2n poles (n = 3, 4 ,.
...) and a rotor magnetized to have a first and a second extension, and are formed in a substantially U-shape. The tips of the first and the second extension are separated by an electrical angle of about 180 °. 1 and 2
First and second stators each having a magnetic pole portion formed therein, the first and second stators being in the same plane, and the first magnetic pole portion of the first stator and the second magnetic pole portion of the second stator. The first magnetic pole portion of the stator is separated by 180 electrical degrees or more, and the second magnetic pole portion of the first stator and the second magnetic pole portion of the second stator are 180 electrical degrees or more. By arranging them at positions separated from each other, 4n magnetically stable points were provided per one rotation of the rotor.

〔Example〕

The present invention will be described below with reference to FIGS. 1 and 2 showing an embodiment used for an interchangeable lens of a single-lens reflex camera.

FIG. 1 is an exploded perspective view of an electromagnetically driven exposure amount adjusting apparatus according to the present invention, and FIG. 2 is a front view of a stepping motor portion.

1 is a ring-shaped 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, 8 is a first armature coil, 9
Is a second armature coil, 10 is a bearing member, and 11 is a flexible printed circuit board.

In FIG. 1, the cam member 1 made of plastic, for example, is provided with groove-shaped cams 1a, 1b, 1c, 1d and 1e equal in number to the plurality of light-shielding blades 2, and the convex portion 15,
1g, 1h and 1i are provided, the optical axis 100 of the convex portions 15, 1g, 1h and 1i
The inner peripheral portion of the rotary ring 3 is fitted with the outer peripheral portion 3a,
The rotating ring 3 is rotatably supported. Also, the convex portion 15,1g,
1h and 1i are provided with holes, and screws 13a, 13b, 13c and 13d (13b to 13d are not shown) are inserted into the screw holes 5a, 5b, 5c and 5d provided in the fixing ring 5 through the holes. By fixing, the cam member 1 is fixed to the fixing ring 5.

For example, the number of the light shielding blades 2 made of plastic is equal to the number of the cams 1a to 1e provided on the cam member 1, but only one is shown in FIG. 1 and the others are omitted.

The first dowel 2a provided on the light shielding blade 2 is the cam member 1
Is fitted to the first cam 1a provided on the
The 2b fits into a first hole 3b provided in the rotating ring 3.

The first and second dowels of the second to fifth light-shielding blades (not shown) are also fitted in the cams provided in the cam member 1 and the holes provided in the rotary ring 3.

The convex portions 15, 1g, 1h, and 1i of the cam member 1 have a height that is larger than the sum of the thickness of the rotating ring 3 and the thickness of the light-shielding blade 2 by a predetermined amount. Fixed ring 5
Screws 13 with rotating ring 3 and shading blade 2 installed.
When fixed by a to 13d, the rotating ring 3 is regulated in its position in the optical axis direction while having a certain backlash. A gear 3f is provided on a part of the outer peripheral portion of the rotating ring 3.

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

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

The third pedestal portion 5h is provided with a hole 5j that is larger than the outer diameter of the rotor 4 by a predetermined amount, and also has a first extension portion 5i for positioning the first stator 6 and a second extension portion 5i. A second extension portion 5m for positioning the stator 7 is provided.

Furthermore, the third pedestal portion 5h is provided with third, fourth, and fifth grooves 5h, 5l, and 5n (the fifth groove 5n is not shown) having steps.

The first stator 6 is made by laminating silicon steel plates, for example, and has a substantially U-shape as shown in FIG. First and second magnetic pole portions 6a and 6c, which face the outer peripheral portion of the rotor 4 with a predetermined gap, respectively, at the tips of the first and second extension portions 6b and 6d of the first stator 6, respectively. (See FIG. 2) are provided. The first and second magnetic pole portions 6a and 6c of the first stator 6 each have an opening angle of about 90 ° in electrical angle and are separated from each other by 180 ° in electrical angle.

The first armature coil 8 is mounted 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 (start and end of winding) of the copper wire 8b are soldered to terminals 8c and 8d press-fitted into the bobbin 8a. It is electrically connected by means such as attachment.

Further, the first stator 6 is provided with a positioning hole 6e.

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

The armature coil 9 is installed in the first extension portion 7b of the second stator 7.

The second armature coil 9 has a bobbin 9a made of plastic, and a copper wire 9b wound around the bobbin 9a.
Both ends (winding start and winding end) of the copper wire 9b are electrically connected to 9c and 9d by means such as soldering. Further, 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 comes 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 the first stator 6 6 and the first positioning pin 5f provided on the fixed ring 5 are fitted together, and as shown in FIG. 2, the first extension 6b of the first stator 6 and the second By fitting the first extending portion 5i of the fixing ring 5 into the gap of the extending portion 6c, the positioning in the direction perpendicular to the optical axis is performed.

The second stator 7 is similar to the first stator 6 in that when the second stator 7 is assembled to the fixed ring 5,
And the third convex portions 5o and 5h are brought into contact with each other to perform positioning in the optical axis direction, and the hole 7e of the second stator 7 and the second positioning pin 5p provided on the fixed ring 5 are fitted to each other. And, as shown in FIG. 2, by fitting the second extension portion 5m of the fixing ring 5 into the gap between the first extension portion 7b and the second extension portion 7d of the second stator 7, Positioning is performed in the direction perpendicular to the optical axis.

The rotor 4 is made of plastic magnet,
The second rotating shafts 4d and 4e, the gear 4c, and the magnetic pole portion 4a are integrally formed. The magnetic pole portion 4a of the rotor 4 has polar anisotropy so that uniform magnetic poles of 8 poles can be formed on the outer peripheral portion. Similarly, magnetization is performed so that uniform magnetic poles of 8 poles can be formed. Has been done. Further, each of the magnetic poles 4a of the rotor 4 is N
A groove 4b is provided at the center of the pole or the S pole. A first rotation shaft 4d of the rotor 4 is rotatably supported by a first bearing 1j provided on 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 of, for example, plastic integral molding, and supports the second rotating shaft 4e of the rotor 4 as a bearing 10.
It has a and the 1st-4th hole 10l, 10m, 10n, 10o. First
~ Through the fourth holes 10l, 10m, 10n, 10o, the first, second
The terminals 8c, 8d, 9c, 9d of the armature coils 8, 9 are guided to the back surface of the bearing member 10 and connected to the flexible printed board 11. The flexible printed board 11 is connected to a drive circuit (not shown).

The bearing member 10 includes the first to fourth protrusions 10b, 10d, 10f,
10i are provided (the second protrusion 10d is not shown), and the first to fifth hooks 10c, 10e, 10g, 10h, 10 are provided on the respective protrusions.
j (the second hook 10e is not shown) is provided. First
~ The fifth hooks 10c, 10e, 10g, 10h, 10j are grooves provided in the fixing ring 5 and having the first to fifth steps, respectively.
The bearing member 10 is fixed to the fixing ring 5 by engaging with 5g, 5q, 5k and 5l and locking the step hook. At this time,
The positioning of the bearing member 10 in the direction perpendicular to the optical axis is performed by the first positioning pin 5f of the fixed ring 5, the first positioning hole 10p of the bearing member 10, the second positioning pin 5p of the fixed ring 5, and the bearing. The second positioning holes 10q of the member 10 are formed by fitting them together.

Next, referring to FIG. 2, 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.

As described above, the magnetic pole portions 6a and 6c, 7a and 7c have an electrical angle of 90 °.
The first magnetic pole portion 6a and the second magnetic pole portion 6c of the first stator 6 are separated from each other by an electrical angle of 180 °. 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 6a of the first stator 6 and the second magnetic pole portion 7c of the second stator 7 have an electrical angle of 63
They are separated by 0 °, which is equivalent to a phase difference of 90 ° between the first stator 6 and the second stator 7, and is a well-known two-phase stepping motor driving method (1-2 phase). By excitation, two-phase excitation, etc.), the diaphragm device can be driven to a predetermined diaphragm value or returned to the open position by a command from the camera.

Next, the cogging torque of the stepping motor which is the drive source of the electromagnetically driven exposure amount adjusting apparatus according to the present invention will be described with reference to FIGS.

When the second stator 7 is removed from the state shown in FIG. 2 and the cogging torque is measured, the cogging torque acting between the first stator 6 and the rotor 4 is A in FIG. The characteristics shown by are shown. However, the horizontal axis in FIG. 3 represents the rotational position of the rotor 4 expressed in electrical angle. When the cogging torque is measured with the first stator 6 removed, the cogging torque acting between the second stator 7 and the rotor 4 has a characteristic as shown by B in FIG. . When the cogging torque is measured with both the first and second stators 6 and 7 attached,
The characteristics are as shown by AB in the figure. As is clear from this characteristic, the stepping motor, which is the drive source of the electromagnetic exposure amount adjusting apparatus according to the present embodiment, has a stable stop position due to the cogging torque which is twice the number of the magnetic poles during one rotation of the rotor 4. And its position is equal to the one-phase energization position.

Further, the above-mentioned embodiment is an example of the diaphragm device used for the interchangeable lens of the single-lens reflex camera, but it is obvious that it can be used also as a shutter device of a compact camera.

[Advantages of the Invention] As described above, in the exposure amount adjusting device having the plurality of light-shielding blades and the stepping motor for driving the plurality of light-shielding blades, the stepping motor has 2n poles (n
= 3,4, ...) and a substantially C-shaped rotor having first and second extension portions, and the ends of the first and second extension portions have an electrical angle. A first and a second stator having first and second magnetic pole portions that are separated by approximately 180 °, wherein the first and second stators are in the same plane, and The first magnetic pole portion and the first magnetic pole portion of the second stator are separated from each other by an electrical angle of 180 ° or more, and the second magnetic pole portion of the first stator and the second magnetic pole portion of the second stator are separated from each other. 180 ° electrical angle with the magnetic pole
By arranging them at positions separated from each other as described above, a number of magnetically stable points can be provided in the two-dimensional arrangement of the stator, so that high diaphragm precision can be easily achieved without exhausting the battery even during long-time exposure. Moreover, the effect that it can be obtained stably is obtained.

Further, by forming a groove in the rotational axis direction at the magnetic pole center position of each pole in the rotor, even when the position of the stator is deviated, the number of magnetic fields which is twice the number of letters of the rotor is generated by one rotation of the rotor. A stable point can be established. Therefore,
It is possible to provide an exposure amount adjusting apparatus in which the allowable range of the stator position is widened and which is highly accurate and does not reduce productivity.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an electromagnetically driven exposure amount adjusting apparatus embodying the present invention, and FIG. 2 is an explanatory view of a stepping motor portion which is a driving source of the electromagnetically driving exposure amount adjusting apparatus according to the present invention. FIG. 7 is an explanatory diagram of cogging torque of the electromagnetically driven exposure amount adjusting apparatus according to the present invention. 1 ... Cam member 2 ... Shading blade 3 ... Rotating ring 4 ... Rotor 5 ... Fixing ring 6,7 ... Stator 10 ... Bearing member 11 ... Flexible printed circuit board

Claims (2)

(57) [Claims] 1. An exposure amount adjusting device having a plurality of light-shielding blades and a stepping motor for driving the plurality of light-shielding blades, wherein the stepping motor is magnetized into 2n poles (n = 3, 4, ...). And a rotor and a first and a second extension portion are formed into a substantially U-shape, and the tips of the first and second extension portions have an electrical angle of about 180 °.
A first and a second stator having first and second magnetic pole portions spaced apart from each other, wherein the first and second stators are coplanar with each other, and The magnetic pole portion and the first magnetic pole portion of the second stator are separated from each other by an electrical angle of 180 ° or more, and the second magnetic pole portion of the first stator and the second magnetic pole portion of the second stator are separated from each other. Is disposed at a position separated by 180 ° or more in terms of electrical angle, thereby providing 4n magnetically stable points per one rotation of the rotor. 2. The exposure amount adjusting apparatus according to claim 1, wherein a groove in the direction of the rotation axis is formed in the rotor at the magnetic pole center position of each pole.