JPH02178640A - Step motor for camera - Google Patents

Abstract

PURPOSE:To stop a photographing lens at various focusing positions and to finely control diaphragm by providing a rotor composed of a multi-polar- magnetized permanent magnet rotatably supported, plural stators facing the rotor, and two-phase electromagnetic coils wound round them, and exciting one or two phases of the electromagnetic coils. CONSTITUTION:The rotor R composed of the four-polar-magnetized permanent magnet is attached to the output shaft of a step motor in the direction of a diameter; the rotor R is rotatably supported by a supporting plate. The two stators Sa and Sb re attached to the supporting plate so that they face the rotor 4, and the electromagnetic coils La and Lb are wound around the foot parts 7b and 8b, respectively, which are provided with the magnetic poles 10 and 12 of the stators Sa and Sb, respectively. A control circuit 14 generates and outputs a pulse signal according to distance information; a driving circuit 13 energizes the electromagnetic coils La and Lb with an exciting current for rotating the rotor R. Since one or two phases of the two-phase electromagnetic coils are excited, the photographing lens can be stopped at various focusing positions and diaphragm can be finely controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a step motor for a camera that drives a drive member that moves a photographic lens to a focusing position or operates a sector mechanism.

[Conventional technology]

In recent years, compact cameras that automatically adjust focus and exposure have been developed. In such an auto-focus auto-exposure compact camera, moving the photographic lens to the focusing position and operating the sector mechanism are performed by a drive member, and this drive member is used for the camera. Driven by a step motor.

Therefore, as a step motor for such a camera, there is a motor as shown in Fig. 7, for example.
(See Publication No. 1683). In the figure, 101 is a rotor made of permanent magnets magnetized with four poles in the radial direction, and this rotor 101 is rotatably supported by a support plate 102. Also, two stators 103.10 are mounted on the support plate 102.
4 is attached to face the rotor 101, and the stators 103 and 104 are each formed in a U-shape and have a pair of legs 105a, 105b and 106a,
106b. At the tips of the leg portions 105a, 105b and 106a, 106b of the stators 103 and 104 facing the outer periphery of the rotor 101, there are magnetic pole portions 1, respectively.
07°108 and 109.110 are provided.

Of these, the magnetic pole portions 107 and 108 have a positional relationship where the angle α with respect to the center of the rotor 101 is 90°, and similarly the magnetic pole portions 109 and 110 have a positional relationship where the angle a is 90′. One of the magnetic pole parts 107.109 of the stator 1G3.104 is close to each other, and this magnetic pole part 1
07.109 has an angle β of 4 with respect to the center of the rotor 101.
The positional relationship is 5@.

The legs 105b and 106b on which the other magnetic poles 108 and 110 of the stators 1G3 and 104 are provided have electromagnetic coils 11
1.112 is wound, and this electromagnetic coil 111,
112 is connected to a drive circuit 113. , drive circuit 1
Reference numeral 13 supplies an exciting current to two-phase electromagnetic coils 111 and 112, and the direction of this exciting current is positive (+).
This is a bipolar-driven two-phase excitation method in which this excitation current is simultaneously applied to two-phase electromagnetic coils 111 and 112 in response to pulse signals from a control circuit (not shown). .

Here, when the drive circuit 113 energizes the electromagnetic coils 111 and 112, each magnetic pole portion 1 of the stators 103 and 104
A predetermined magnetic field is generated at 07.108 and 109.degree. 110, and FIG. 8 shows a pulse signal outputted from the control circuit to the drive circuit 113 for this purpose. As shown in this figure, when positive (+) and negative (-) excitation currents are applied from the drive circuit 113 to the two-phase electromagnetic coils 111 and 112 in response to the pulse signal, as shown in FIG. (b).

As shown in (c), the magnetic pole parts 107, 108°109.1
A magnetic field is generated at 10, and the rotor 101 rotates. The drive member is driven by the rotation of the rotor 101 via a gear mechanism to move the photographing lens to the in-focus position or to operate the sector mechanism.

[Department notification that the invention attempts to solve]

However, in such a conventional camera step motor, the two-phase electromagnetic coil 1 is connected to the drive circuit 113.
It was a bipolar drive two-phase excitation system in which positive (+) and negative (-) excitation currents were applied simultaneously to 11 and 112.

By the way, in a camera having a large number of focal lengths, the photographic lens must be moved and stopped at a large number of focus positions according to distance measurement information. Furthermore, in a camera with high aperture accuracy, the aperture must be finely controlled according to subject brightness information, and the sector mechanism must be provided with a large number of stopping positions. Therefore, a large number of stopping positions for the drive member driven by the camera step motor must be provided, that is, the number of steps of the camera step motor must be increased.

However, because conventional camera step motors use a two-phase excitation method, the step angle is large, and the number of steps is limited due to limitations such as the operating space of the drive member and the space of the gear train from the motor to the drive member. I couldn't do too many.

Therefore, there are problems in that the photographic lens cannot be stopped at many focusing positions, and the sector mechanism cannot be provided with many stopping positions.

[Means to solve the problem]

In order to solve such problems, in the present invention,
A step motor for a camera that drives a drive member that moves a photographic lens to a focusing position or operates a sector mechanism, and is a rotor that is rotatably supported and made of a permanent magnet that is multi-pole magnetized in the radial direction. A configuration comprising: a plurality of stators disposed facing the rotor; and a two-phase electromagnetic coil wound around the stator, and the two-phase electromagnetic coil is excited in 1-2 phases. That is.

[For production]

When the two-phase electromagnetic coil is excited in 1-2 phases, the step angle of this step motor becomes 1/2, and the amount of drive per pulse of the drive member becomes 1/2 compared to the conventional one. Therefore, the stopping position of the driving member is doubled compared to the conventional method. Therefore, even if the camera has a large number of focal lengths and a high aperture precision, the photographic lens can be stopped at a large number of in-focus positions, and the aperture can be finely controlled.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. 1st
4 through 4 are diagrams showing a first embodiment of a step motor for a camera according to the present invention.

First, the configuration will be explained.

In FIG. 1, reference numeral 1 denotes a photographic lens that moves to a number of focusing positions according to distance measurement information, and this photographic lens 1 is fixedly supported by a lens frame 2. As shown in FIG.

A protrusion 2b is integrally formed on the lens frame 2, and the protrusion 2b abuts against a cam surface 3a of a lens drive cam 3, which serves as a drive member and is supported so as to be movable in the left-right direction in the figure. Further, the lens frame 2 has a protrusion 2b on a cam surface 3a.
A tension spring 2a is attached which urges downward in the figure so as to be in constant contact with the spring 2a. A rack 3b is formed on the surface of the drive member 3 opposite to the cam surface 3a (lower side in the figure), and this rack 3b is connected to an output gear attached to the output shaft of the step motor via a pinion 6 and an idler 4. It meshes with 5.

A rotor R consisting of a permanent magnet magnetized with four poles in the radial direction is attached to the output shaft of the step motor.
is rotatably supported by a support plate (not shown). Further, two stators Sa and Sb are attached to the support plate so as to face the rotor R, and each of the stators Sa and sb is formed into a U-shape and has a pair of leg portions 7a,
It has 7b, ga, and gb. Magnetic pole portions 9, 10° 11, 12 are provided at the tips of the leg portions 7a, 7b of the stators Sa and sb and ga, gb facing the outer periphery of the rotor R. Of these, the magnetic pole parts 9 and 10 are rotor R
The angle α with respect to the center of the stators Sa and Sb is in a positional relationship of 90'', and similarly the angle α of the magnetic pole portions 11 and 12 is also in a positional relationship of 90＠.One of the magnetic pole portions of stators Sa and Sb is 9° are close to each other, and this magnetic pole part 11°1
2 has a positional relationship where the angle β with respect to the center of the rotor R is 45@. The other magnetic field of stators Sa and Sb +! 10
．． Leg portion 7b provided with 12.

Electromagnetic coils La and Lb are wound around 8b.

The two-phase electromagnetic coils La and Lb have positive (+) or negative (
-) is connected to a drive circuit 13 that applies an excitation current, and a control circuit 14 that generates and outputs a pulse signal is connected to this drive circuit 13. Furthermore, the distance to the subject is determined by 71) I
A distance measuring section 15 is connected thereto. When the distance to the subject is measured by the distance measuring section 15, this distance information is output as a signal to the control circuit 14. The control circuit 14 generates a pulse signal according to the distance information and outputs it to the drive circuit 13, and in response, the drive circuit 13 energizes the electromagnetic coils La and Lb with an excitation current for rotating the rotor R.

Next, the operation will be explained with reference to a flowchart of the operation of the camera step motor shown in FIG. The control circuit 14 is activated by the release operation, but if the rotor R of this compact camera has slightly deviated from the initial stable point (initial position) due to vibration or impact, first move the rotor R to the initial position. Must be set to . Therefore, the O-th pulse signal is output from the control circuit 14 to the drive circuit 13, and the excitation current is applied to the two-phase electromagnetic coils La and L.
b is energized to set the rotor R to the initial position.

Next, the distance to the subject is measured by the distance measuring section 15, and when this is output as a distance measurement information signal to the control circuit 14, the number of steps for focusing (AFS) is determined by the control circuit 14. be done. For example, when AFS is 8, as shown in Fig. 3, two-phase electromagnetic coils La, L
A pulse signal is outputted to the drive circuit 13 to repeatedly excite the pulse signal b in one phase and two phases alternately. Positive (+) or negative (-
) may be applied to two phases at the same time for excitation, or may be applied to only one phase for excitation. Simultaneous excitation of two phases of the two-phase electromagnetic coils I, a, and Lb and excitation of only one phase are performed alternately. Note that a method in which only one phase is excited and two phases are simultaneously excited is called a 1-2 phase excitation force method. When the electromagnetic coils La and Lb are excited in this way, FIG.
a).

As shown in (b) and (c), a magnetic field is generated in the magnetic pole portions 9, 10, 11, and 12 of the stators Sa and Sb, and the rotor R rotates clockwise and stops at the position of the 8th pulse.

The rotation of rotor R is controlled by output gear 5. The signal is transmitted to the rack 3b of the lens drive cam 3 via the idler 4° pinion 6, etc., and the lens drive cam 3 moves in parallel to the left in FIG.

When the lens driving cam 3 moves in parallel, the photographing lens 1 is retracted downward in the figure by the cam 3a and stops at a focus position corresponding to an 8-pulse signal. Next, the sector mechanism (
(not shown) performs the exposure operation. When the exposure operation is finished,
A pulse signal for rotating the rotor R in the opposite direction to the rotation direction is output from the control circuit 14 to the drive circuit 13, and the two-phase electromagnetic coils La and Lb are excited to rotate the rotor R in the opposite direction. Return to the initial position.

Here, the rotor R has four poles and the stator Sa.

Regarding the magnetic pole part 9.10.11.12 of sb, in a step motor configured with α angle of 90@ and β angle of 45'', according to the conventional two-phase excitation force type, as shown in Fig. 9 ( b
), the step angle θl is 45'. However, in the case of a 1-2 phase excitation force type as in the present invention, the third
As shown in the figure, two-phase excitation occurs during even-numbered pulses, and one-phase excitation occurs during odd-numbered pulses, making it possible for the rotor R to stop at an intermediate position between conventional stopping positions. Therefore, in the case of the 1-2 phase excitation force type, the step angle θ2 of the rotor R is θ2-
θl/2-45"/2-22.5@. That is,
The amount of drive per pulse of the lens drive cam 3 due to the rotation of the rotor R is 1/2 compared to the conventional two-phase excitation force type, and the amount of extension and retraction of the photographic lens 1 is also 1/2 compared to the conventional one. . Therefore, the stopping position of the lens drive cam 3 is twice as large as that of the conventional system even if the specifications of the gear mechanism such as the output gear 5, idler 4, and pinion 6 are exactly the same. Therefore, in a compact camera having many focal lengths, the photographing lens 1 can be stopped at many focusing positions.

On the other hand, in order to stop the photographic lens 1 at a focus position according to a number of focal lengths, it is necessary to increase the drive stroke amount of the lens drive cam 3 or to move the lens drive cam 3 and rotor R.
It is conceivable to increase the reduction ratio of the gear mechanism interposed between the two. In other words, it is possible to add a new idler or increase the outer diameter of the gear. However, in a compact camera that does not have extra space, it is not possible to add an idler or increase the outer diameter of the gear due to its configuration. However, with the camera step motor of the present invention, no extra space is required for the compact camera, and no problem arises in the configuration.

On the other hand, if the number of steps of this step motor is the same as before, it is possible to reduce the drive stroke amount of the lens drive cam 3 and reduce the reduction ratio of the gear mechanism, making the compact camera even more compact. can do.

Here, it is possible to speed up the rotation of the rotor by shortening the pulse time per pulse using the control circuit, but in this case, there is a limit to the responsiveness of the step motor and the cost will be high. There is a problem with putting it away. However, with the steering knob motor of the present invention, such problems do not occur.

Next, a second embodiment of the camera step motor according to the present invention is shown in FIG. The configuration of this embodiment is similar to the previous embodiment. Furthermore, in this embodiment, when the electromagnetic coils 1, a, and Lb are excited by the pulse signal of the control circuit 14,
The above-mentioned 1-2 phase excitation method and the conventional 2-phase excitation method can be selected.

FIG. 5 is a flowchart showing the operation of this camera step motor, and the explanation will be made with reference to this flowchart. When the ranging unit 15 outputs the All axis information signal to the control circuit 14, the control circuit 14
S is determined, and the rotor R is rotated by a two-phase excitation method by a pulse signal from the control circuit 14 until immediately before this AFS (in this embodiment, two steps before). Next, until AFS, 1-
The rotor R is rotated by a two-phase excitation method.

Here, the pulse time (per pulse) of the pulse output from the control circuit 14 to the drive circuit 13 is 1-2
The settings are the same during phase excitation. Therefore, the rotation speed of the rotor R during 2-phase excitation is twice as fast as the rotation speed during 1-2 phase excitation, and the rotation speed of the rotor R during 2-phase excitation is twice as fast as the rotation speed during 1-2 phase excitation. can be moved to Therefore, even if the subject is moving at high speed, the subject can be photographed.

Next, an exposure operation is performed by the sector mechanism, and when this is completed, a pulse signal for reversing the rotor R is output from the control circuit 14 to the drive circuit 13 in a two-phase excitation method. Therefore, the photographing lens 1 quickly returns to the initial position in the backward stroke of this drive range.

Further, even if the number of steps is twice the number of steps in the conventional example, the photographing lens 1 can be moved to the in-focus position without delay. Therefore, even if the subject is moving at high speed, the subject can be photographed. In addition, A
If the rotor R is rotated using the 1-2 phase excitation method not only immediately before FS but also at the beginning of AFS, the rotor R will smoothly stand up. Furthermore, since the 2t[l excitation simultaneously energizes the two-phase electromagnetic coils, a larger output torque can be obtained for boat fishing than the 1-2 phase excitation. By configuring the tension spring 2a to be charged by the motor, the motor can be made smaller and the power consumption can be reduced.

Next, a third embodiment of the camera step motor according to the present invention is shown in FIG. In this embodiment, the output gear 5
The aperture drive member 21 is connected to the idler 4 and the pinion 6 via the idler 4 and the pinion 6.
The gears 21a are in mesh. When the diaphragm drive member 21 is rotated by the camera step motor, the sector mechanism 22 is operated and the diaphragm aperture 23 is changed. When the brightness information of the subject is input manually to the control circuit 14, an excitation current is applied from the drive circuit 13 to the electromagnetic coils La and Lb.
Rotor R is rotated. When the rotor R is rotated, this rotation is transmitted to the aperture drive member 21 via the output gear 5, idler 4, and pinion 6, and the sector mechanism 22 is activated.

Since it operates in the same manner as the previous embodiment, in a camera with high aperture accuracy, the sector mechanism can be provided with many stopping positions, and the aperture can be finely controlled in accordance with subject brightness information. Also in this example, 1-
It is also possible to make it possible to select between the two-phase excitation method and the two-phase excitation method, and even in this case, the same functions and effects as in the embodiment described above can be obtained.

Furthermore, in the first to third embodiments described above, a four-pole rotor and two U-shaped stators were used.
-221860) has similar actions and effects.

〔Effect of the invention〕

As explained above, according to the present invention, since the two-phase electromagnetic coil is excited in one to two phases, the number of steps of the camera step motor can be increased. Therefore, even if the camera has a large number of focal lengths and a high aperture precision, the photographic lens can be stopped at a large number of focusing positions, and the aperture can be precisely controlled.

On the other hand, if the number of steps of this camera step motor is kept the same, it is possible to reduce the drive stroke amount of the drive member and reduce the reduction ratio of the gear mechanism, making this compact camera even more compact. be able to.

Next, the two-phase electromagnetic coil is excited in two phases in most of the drive range of the drive member, and the stop position of the drive member is set based on at least information such as object distance and object brightness. If the two-phase electromagnetic coil is excited in 1-2 phases in the range from immediately before to this stop position, the photographing lens can be quickly moved to the in-focus position, and the sector mechanism can be quickly activated. Therefore, even if the subject is moving at high speed, the subject can be photographed.

Further, the two-phase electromagnetic coil is excited in one or two phases in at least a part of the forward stroke of the drive range of the drive member, and the two-phase electromagnetic coil is excited in two phases in the backward stroke of the drive range, The photographic lens and sector mechanism can be quickly returned to their initial positions.

[Brief explanation of the drawing]

1 to 4 are diagrams showing a first embodiment of a step motor for a camera according to the present invention, FIG. 1 is an overall configuration diagram thereof, and FIG. 2 is a flow chart showing the operation of this step motor for a camera. , FIG. 3 is a waveform diagram of a pulse signal output from this control circuit, and FIGS. 4(a), (b), and (c) are diagrams showing rotational drive of this rotor. FIG. 5 is a diagram showing a second embodiment of a step motor for a camera according to the present invention;
, and a flowchart showing its operation in detail. FIG. 6 is an overall configuration diagram showing a third embodiment of a step motor for a camera according to the present invention. 7 to 9 are diagrams showing a conventional camera step motor. FIG. 7 is a plan view of this motor, FIG. 8 is a waveform diagram of a pulse signal output from this control circuit, and FIG. a), (b), (c)
is a diagram showing the rotational drive of this rotor. 1... Photographing lens 2... Lens frame 3... Lens drive cam 5... Output gear rod... Pinion 9-12... ... Magnetic pole section 13 ... Drive circuit 14 ... Control circuit 15 ... Distance measuring section R ... Rotor Sa, Sb ... Stator La, Lb... Electromagnetic coil or above Applicant Seikosha Co., Ltd.

Claims (3)

[Claims] (1) A step motor for a camera that drives a drive member that moves the photographing lens to the focusing position or operates the sector mechanism, and is a permanent magnet that is rotatably supported and multi-pole magnetized in the radial direction. A rotor consisting of a rotor, a plurality of stators arranged opposite to the rotor, and a two-phase electromagnetic coil wound around the stator, and the two-phase electromagnetic coil is excited in one to two phases. A step motor for cameras, which is characterized by: (2) The two-phase electromagnetic coil is excited in two phases in most of the drive range of the drive member, and the stop position of the drive member is set based on at least information such as subject distance and subject brightness. 2. The step motor for a camera according to claim 1, wherein the two-phase electromagnetic coil is excited in one to two phases in the range from immediately before to this stop position. (3) The two-phase electromagnetic coil is 1-2 phase excited during at least part of the forward stroke of the drive range of the drive member, and the two-phase electromagnetic coil is 2-phase excited during the backward stroke of the drive range. A step motor for a camera according to claim 1, characterized in that: