JP2005024802A - Driving mechanism for camera and driving method for step motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving mechanism for a camera including a step motor by which power saving is realized with simple structure. <P>SOLUTION: The driving mechanism for the camera includes a step motor equipped with a rotor having four magnetic poles, a stator including a 1st magnetic pole excited by a 1st coil, a 2nd magnetic pole excited by a 2nd coil, and a 3rd magnetic pole excited by the 1st and the 2nd coils, and a current supply switching means for switching the case a current is supplied to the 1st and the 2nd coils and the case a current is supplied to either the 1st coil or the 2nd coil, and a sector for opening/closing an aperture for photography by the step motor, and is constituted so that the current supply switching means supplies the current to the 1st and the 2nd coils when it allows the sector to close the aperture for photography, and it supplies the current to either coil when it allows the sector to open the aperture for photography. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a small step motor capable of efficiently reducing power consumption. The present invention also relates to a camera drive mechanism employing the step motor.
[0002]
[Prior art]
In recent years, cameras have been digitized, and a diaphragm or a shutter is driven by a step motor. In this type of camera, it is desirable to have a structure that can quickly drive drive portions such as aperture blades and shutter blades when necessary, while suppressing battery consumption. For example, there is Patent Document 1 regarding driving of a step motor of a camera. In this patent document 1, a step motor driving method in which a two-phase excitation method is used to quickly drive the aperture opening / closing mechanism to a position near the final stop position, and a small portion up to the final stop position thereafter is a 1-2 phase excitation method. Has proposed. According to this proposal, since it is possible to narrow down to a required aperture value in a short time, the time lag can be reduced, and the accuracy of the aperture value at the time of completion is improved.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-18492
[Problems to be solved by the invention]
However, the driving method disclosed in Patent Document 1 only proposes a technique for accurately performing position control when a diaphragm opening / closing mechanism is driven by two-phase excitation using a conventional general stepping motor. . Thus, no consideration has been given to reducing the power consumption of the step motor, as pointed out above. Further, in the driving method disclosed in Patent Document 1, since the step motor is switched from 2-phase excitation to 1-2 phase excitation while the aperture opening / closing mechanism is being driven, the data creation and control system for that is complicated. There is a problem that this causes an increase in cost.
[0005]
Therefore, an object of the present invention is to provide a camera drive mechanism including a step motor that solves the above-described problems and can achieve power saving with a simple structure. In addition, a driving direction of the step motor that can suppress power consumption is also provided.
[0006]
[Means for Solving the Problems]
The object is to provide a rotor having four magnetic poles, a first magnetic pole excited by a first coil, a second magnetic pole excited by a second coil, and a first magnetic pole excited by the first and second coils. A stator including three magnetic poles, a case where current is supplied to the first coil and the second coil, and a case where current is supplied to one of the first coil and the second coil. A step motor provided with a current supply switching means for switching, and a sector moved by the step motor between a position for closing a photographing opening formed on a substrate and a position for opening the photographing opening. The supply switching means supplies current to the first coil and the second coil when the sector is in the closing position, and when the sector is in the opening position, the first coil and the second coil. The is achieved by the camera of the drive mechanism for supplying the second either one current coil.
[0007]
According to the present invention, the current supply switching means supplies current to either the first coil or the second coil in the case of two-phase excitation for supplying current to the first coil and the second coil. Since it is possible to switch between the case of single-phase excitation, it is possible to provide a camera drive mechanism that can selectively use a form that places importance on the drive speed of the rotor and a form that places importance on power consumption. The camera drive mechanism can reduce power consumption by utilizing the time when the rotational speed of the rotor is not required.
[0008]
The rotor has a cylindrical shape, the stator has a planar U-shape, the stator is disposed to face the outer peripheral surface of the rotor, and the first magnetic pole and the A structure in which the second magnetic pole is set and the third magnetic pole is set in the center position of the stator can be adopted as an example. By providing such a structure, the rotor can be stopped and driven with high positional accuracy. The sector can include a shutter blade, and it is possible to realize a structure in which the shutter is quickly driven with an emphasis on speed when the shutter blade is closed, and the shutter is driven relatively slowly by an energy saving type when the shutter blade is opened.
[0009]
In the present invention, a rotor having four magnetic poles, a first magnetic pole excited by a first coil, a second magnetic pole excited by a second coil, and excited by the first and second coils. A step motor driving method including a stator including a third magnetic pole, wherein a current is supplied to the first coil and the second coil, and the first coil and the second coil. It is possible to include a step motor driving method that switches between supplying a current to one of the coils and driving the rotor. According to this method, the step motor can be driven in a power saving manner when necessary.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a main part of the step motor according to the embodiment. The step motor 1 includes a rotor 2 that can be rotated in both directions disposed in the center, and a stator 3 that is disposed so as to face the outside of the rotor 2. The rotor 2 has a circular cross section and a cylindrical shape. The stator 3 is formed in an integral shape with a substantially U-shaped plane, and is arranged in a state in which the rotor 2 is accommodated in the internal space. In FIG. 1, the step motor 1 is shown in a state where the open side of the U-shape of the stator 3 faces upward.
[0011]
The rotor 2 has a four-pole configuration including two N-poles and two S-poles. The rotor 2 is a permanent magnet in which the same magnetic poles are magnetized at positions facing each other, and is set so as to be rotatable around the shaft 21 in both directions. Both ends of the stator 3 having the U-shape are formed so as to face the peripheral surface of the rotor 2. Each of these becomes the first magnetic pole 11 and the second magnetic pole 12. A third magnetic pole 13 is disposed at an intermediate position between the first magnetic pole 11 and the second magnetic pole 12.
[0012]
A first coil 4 is wound between the first magnetic pole 11 and the third magnetic pole 13, and a second coil 5 is wound between the second magnetic pole 12 and the third magnetic pole 13. The first magnetic pole 11 is excited when the first coil 4 is energized, and the second magnetic pole 12 is excited when the second coil 5 is energized. On the other hand, the third magnetic pole 13 is excited by both the first coil 4 and the second coil 5. Therefore, the excited state of the third magnetic pole 13 appears as an apparent state that is a combination of the energized states of the first coil 4 and the second coil 5.
[0013]
The step motor 1 includes a current control circuit 25 as current supply switching means. A current for exciting the first coil 4 and the second coil 5 is supplied from the current control circuit 25. The current control circuit 25 supplies current to the first coil 4 and the second coil 5 to perform two-phase excitation, and the current control circuit 25 supplies current to one of the first coil 4 and the second coil 5. And a current switching function for switching between the case of performing one-phase excitation. This switching function is executed based on a request signal on the side of an electronic device such as a camera to which the step motor 1 is applied. In the two-phase excitation pattern in which current is supplied to the first coil 4 and the second coil 5, the first magnetic pole 11 and the second magnetic pole 12 are excited. Can do. On the other hand, in the one-phase excitation pattern in which a current is supplied to one of the coils 4 and 5, one of the first magnetic pole 11 and the second magnetic pole 12 is excited, so that power consumption can be suppressed. The two-phase excitation pattern and the one-phase excitation pattern executed by the current control circuit 25 are as follows.
[0014]
In the two-phase excitation pattern, a current for exciting both the first coil 4 and the second coil 5 is supplied from the current control circuit 25, and the driving state of the rotor 2 is switched by switching the current supply direction for each coil. Is controlled. In this pattern, there are a state in which the first magnetic pole 11 and the second magnetic pole 12 are both excited by the same magnetic pole and a state in which they are excited by different magnetic poles. At this time, when the first magnetic pole 11 and the second magnetic pole 12 are both excited by the same magnetic pole, the magnetic field that appears as a result of the third magnetic pole 13 becomes stronger than these. On the other hand, when the first magnetic pole 11 and the second magnetic pole 12 are excited to different magnetic poles, the magnetization at the third magnetic pole 13 cancels out and becomes a non-magnetized state.
[0015]
In the one-phase excitation pattern, a current for exciting either the first coil 4 or the second coil 5 is supplied from the current control circuit 25, and the driving state of the rotor 2 is controlled by switching the current supply direction. Is done. In the case of this one-phase excitation pattern, only the first magnetic pole 11 side or the second magnetic pole 12 side is excited and switched to the opposite magnetic pole by changing the current supply direction. The third magnet 13 in this one-phase excitation pattern is excited by a magnetic pole that is a counter electrode of the excited first magnetic pole 11 or second magnetic pole 12.
[0016]
Furthermore, with reference to FIGS. 2-4, the mode at the time of the rotor 2 of this step motor 1 rotating is demonstrated in detail. FIG. 2 shows a case of a two-phase excitation pattern, in which the rotor 2 is rotated by exciting the first coil 4 and the second coil 5. FIGS. 3 and 4 show the above-described one-phase excitation pattern, in which only one of the first coil 4 and the second coil 5 is excited to rotate the rotor 2. . 3 particularly shows a case where the first coil 4 is excited, and FIG. 4 shows a case where the second coil 5 is excited. The current supply to the coils 4 and 5 shown in FIGS. 2 to 4 is performed by the current control circuit 25 shown in FIG. 1, but the illustration is omitted in these drawings. In FIGS. 3 and 4, only the energized coil is shown for easy understanding.
[0017]
A state when the rotor 2 of the step motor 1 rotates will be described with reference to FIG. FIG. 2 shows the above-described two-phase excitation pattern, in which the first coil 4 and the second coil 5 are excited to rotate the rotor 2 clockwise (in the clockwise direction) at a step angle of 45 °. Shows when to do. FIG. 2A shows a state where the coils 4 and 5 are not energized. FIGS. 2B to 2E show the time series in which the current supplied to the coils 4 and 5 is controlled to rotate the rotor 2 clockwise. In FIG. 2A, the coils 4 and 5 are not energized and the first magnetic pole 11 and the second magnetic pole 12 are not excited, but the N and S magnetic poles are opposed to the first and second magnetic poles 11 and 12, respectively. Retained.
[0018]
FIG. 2B shows a case where the first and second coils 4 and 5 are energized from the state of FIG. 2A and both the first magnetic pole 11 and the second magnetic pole 12 are excited to the S pole. Yes. At this time, the N pole is doubled and excited in the third magnetic pole 13. Next, FIG. 2C shows a case where the excitation state of the first magnetic pole 11 is maintained at the S pole from the state of FIG. 2B and the second magnetic pole 12 is excited at the opposite N pole. Yes. At this time, since the N pole and the S pole are excited in the third magnetic pole 13, they cancel each other and become a non-magnetized state. Similarly, FIG. 2D shows a case where both the first magnetic pole 11 and the second magnetic pole 12 are excited to the N pole from the state of FIG. At this time, in the third magnetic pole 13, the S pole is doubled and excited. Next, FIG. 2E shows a case where the excitation state of the first magnetic pole 11 is maintained at the N pole from the state of FIG. 2D and the second magnetic pole 12 is excited to the opposite S pole. . At this time, since the N pole and the S pole are excited in the third magnetic pole 13, they cancel each other and become a non-magnetized state.
[0019]
As described above, as the magnetization state of each of the magnetic poles 11 to 13 on the stator 3 side changes sequentially, the rotor 2 rotates 45 degrees clockwise as shown in the figure. 2 shows the rotor 2 in a position where the first and second coils 4 and 5 are energized and the rotation of 45 ° is completed. In the two-layer excitation pattern shown in FIG. 2, a relatively strong magnetic field can be applied to the rotor 2, so that the rotor 2 can be rotated at a high speed. The first and second magnetic poles 11 and 12 can be accurately positioned at the opposing positions.
[0020]
FIG. 3 shows a case where the rotor 2 is rotated by a step angle of 90 ° in the clockwise direction by one-phase excitation in which only the first coil 4 is excited. FIG. 3A shows a state where the coils 4 and 5 are not energized. FIGS. 3B to 3E show the time series in which the current supplied to the coil 4 is controlled to rotate the rotor 2 clockwise by 90 °. In the case of FIG. 3, the magnetic pole generated in the first magnetic pole 11 is reversed by switching the current supplied to the first coil 4 in the reverse direction. At this time, the magnetic pole generated in the third magnetic pole 13 is a magnetic pole opposite to the first magnetic pole. Further, since the second magnetic pole 12 is not excited by the coil, it becomes an integral magnetic pole with the third magnetic pole 13.
[0021]
3A is the same as FIG. 2A in which the first magnetic pole 11 and the second magnetic pole 12 are not excited, and the N and S magnetic poles of the rotor 2 are the first and second magnetic poles, respectively. The magnetic poles 11 and 12 are held at opposite positions. Next, FIG. 3B shows a case where the first coil 4 is energized from the state of FIG. 3A and the first magnetic pole 11 is excited to the S pole. At this time, the third magnetic pole 13 and the second magnetic pole are excited to the N pole. In FIG. 3C, the excitation state of the first magnetic pole 11 is switched from the state of FIG. 3B to the N pole, and the third magnetic pole 13 and the second magnetic pole 12 are excited to the opposite S pole. Shows the case. Similarly, FIG. 3D shows a case where both the first magnetic poles 11 are excited to the S pole from the state of FIG. At this time, the third magnetic pole 13 and the second magnetic pole 12 are excited to the N pole. Next, in FIG. 3E, the first magnetic pole 11 is switched to the N pole from the state of FIG. 3D, and the third magnetic pole 13 and the second magnetic pole 12 are excited to the opposite S pole.
[0022]
As described above, as the magnetization state of each of the magnetic poles 11 to 13 on the stator 3 side changes sequentially, the rotor 2 rotates 90 ° in the clockwise direction as shown in the figure. 3 shows the rotor 2 in the position where the first coil 4 is energized and the rotation of 90 ° is completed. In the case of the one-phase excitation shown in FIG. 3, in all the states shown in FIGS. 3A to 3E, the two magnetic fields on the rotor 2 side face the first magnetic pole 11 and the second magnetic pole 12, respectively. Therefore, accurate positioning can be executed. In addition, in the example shown in FIG. 3, the rotor 2 is rotated by 90 ° in the clockwise direction with the second coil 5 rested, so that there is a significant merit that the rotor 2 can be driven with power saving.
[0023]
FIG. 4 shows another pattern of single-phase excitation, in which only the second coil 5 is excited to rotate the rotor 2 counterclockwise by a step angle of 90 °. FIG. 4 shows an operation that is just the reverse of that in FIG. Also in the case shown in FIG. 4, as the magnetization state of each of the magnetic poles 11 to 13 on the stator 3 side changes sequentially, the rotor 2 rotates 90 ° in the counterclockwise direction as shown in the figure. Also in the case shown in FIG. 4, the rotor 2 can be rotated counterclockwise while stopping the rotor 2 with high accuracy while saving power while the first coil 4 is rested.
[0024]
As described above, the step motor 1 causes the rotor 2 to generate a strong magnetic attractive force between the rotor 2 by exciting the first and second magnetic poles in two phases by switching the current by the current control circuit 25. It is possible to switch between a case where the rotor is driven quickly and a case where either one of the first magnetic pole and the second magnetic pole is excited by one phase to drive the rotor 2 in an energy saving manner. Therefore, when such a step motor 1 is applied to an electronic device such as a camera, for example, accurate driving and power saving can be achieved.
[0025]
FIG. 5 is a view showing a stator having a preferable shape for use in the step motor 1. In FIG. 5, the same reference numerals are given to the parts corresponding to the parts shown in FIGS. 1 and 2. The first magnetic pole 11 and the second magnetic pole 12 of the stator 3 are formed in a vertically long shape so as to face the circumferential surface of the rotor (not shown) and correspond to the length in the longitudinal direction of the rotor. The stator 3 includes arm portions 31 and 32 on both sides, and the arm portions 31 and 32 are connected to a base portion 35. A third magnetic pole 13 is formed at the center of the base 35. The third magnetic pole 13 is also formed in a vertically long shape similar to the first magnetic pole 11 and the second magnetic pole 12.
[0026]
In the stator 3, coils 4 and 5 for exciting the first to third magnetic poles are wound around the arm portions 31 and 32. In order to position the coils 4 and 5, projections 33 and 34 are formed at the rear ends of the arm portions. By providing the protrusions 33 and 34 as described above, a structure that can reliably position the coils 4 and 5 wound around the arm portions 31 and 32 is realized. In addition, the recessed parts 37-39 are formed in the upper part of each magnetic pole 11-13. The step motor 1 shown in the present embodiment is modularized by setting cases (not shown) on the upper and lower sides thereof. These recesses 37 to 39 are used for positioning when setting the case.
[0027]
Further, with reference to FIGS. 6 to 9, an example in which the step motor 1 is employed as a shutter drive unit of a camera and a drive mechanism is configured will be described below. In the case of a camera, it is desirable that the step motor be driven quickly when closing the shutter blades so as not to miss a photo opportunity. On the other hand, no speed is required when returning the shutter blades. Therefore, this drive mechanism uses the step motor 1 to drive quickly by two-phase excitation when closing the shutter, and to drive relatively slowly by one-phase excitation when returning the shutter, thereby reducing power consumption.
[0028]
FIG. 6A is a diagram schematically illustrating a state in which the step motor 1 is disposed with respect to the shutter substrate 50 in a plan view. As will be described later, the shutter substrate 50 includes a lens opening 51 for photographing. On the front side of the shutter substrate 50, three sectors 60, 65, and 70 are arranged along the substrate surface. These sectors are the first shutter blade 60, the second shutter blade 65, and the diaphragm blade 70 from the shutter substrate 50 side. A step motor 1 is disposed on the back side of the shutter substrate 50.
[0029]
Although the position of the hole cannot be confirmed in FIG. 6A, the first shutter blade 60 has a hole that engages with the protrusion 61 provided on the substrate 50 and a hole that engages with the engagement pin 27 extending from the rotor 2. I have. Similarly, the second shutter blade 65 includes a hole that engages with a protrusion 66 provided on the substrate 50 and a hole that engages with an engagement pin 27 extending from the rotor 2. The aperture blade 70 includes a hole that engages with a protrusion 71 provided on the substrate 50 and a hole that engages with an engagement pin 27 extending from the rotor 2. Each of the first shutter blade 60, the second shutter blade 65, and the aperture blade 70 swings with its own locus along with the rotation operation of the engagement pin 27 described later.
[0030]
An arm portion 26 extending in the radial direction is connected to the rotor 2 of the step motor 1 disposed on the back side of the substrate 50. An engagement pin 27 extending from the end of the arm 26 to the opposite side through an opening 55 provided on the shutter substrate 50 side is connected. The holes provided in each of the first shutter blade 60, the second shutter blade 65, and the aperture blade 70 are engaged with the engaging pin 27 that protrudes to the front side. Therefore, when the rotor 2 of the step motor 1 rotates, the engaging pin 27 rotates in conjunction with this, and the first shutter blade 60, the second shutter blade 65, and the aperture blade 70 follow a predetermined locus. Swing.
[0031]
FIG. 6B is a view showing the movement locus CR of the engagement pin 27. The engagement pin 27 can rotate 360 ° with the rotation of the rotor 2, but the opening 55 formed in the substrate 50 has a fan shape, and a member 29 for restricting the movement of the arm 26 is disposed. . Therefore, in this example, the engagement pin 27 is set to rotate within the predetermined range RE.
[0032]
A case in which the shutter drive mechanism having the above-described configuration is operated will be described with reference to FIGS. FIG. 7 shows a state in which the photographing lens opening 51 provided on the substrate 50 is fully opened. FIG. 8 shows a state in which the lens opening 51 for photographing provided on the substrate 50 is fully closed.
[0033]
In the present drive mechanism, when driving from the open state shown in FIG. 7 to the closed state shown in FIG. 8, the current control circuit 25 of the step motor 1 excites the coils 4 and 5 in two phases, so that the shutter is quickly released. The blade can be closed. On the contrary, when driving from the closed state shown in FIG. 8 to the open state shown in FIG. 7, the current control circuit 25 excites one of the coils 4 and 5 for one-phase to open the shutter blade. To drive. In this case, the movement of the shutter blades is relatively slow, but power consumption is suppressed because there is no influence on photographing. Note that the current control circuit 25 is driven based on a shutter drive signal supplied from a camera-side control circuit (not shown).
[0034]
FIG. 9 is a diagram showing the relationship between the pulse waveform of the coil of the step motor that drives the shutter and the open / close state of the shutter blades. Here, for comparison, the case where the step motor 1 is driven by the conventional type is shown on the left, and the case where it is driven by the power saving type according to the present embodiment is shown on the right. In the case of a conventional step motor, as shown in the left of FIG. 9, when the shutter blade is closed by two-phase excitation, it is driven by two-phase excitation even when it is opened. That is, when closing the shutter blades, both the first coil and the second coil are set to H to close the shutter blades at high speed. When opening the shutter blades, both the first coil and the second coil are set to L to open the shutter blades. However, when opening the shutter blades, in order not to damage the blades at the time of activation, first, the coil on one side is energized in the reverse direction H and then energized in the direction L of opening the shutter blades. In any case, two-phase excitation is employed when the shutter blades are opened.
[0035]
On the other hand, the power saving type shown on the right closes the shutter blades at high speed by setting both the first coil and the second coil to H when closing the shutter blades. However, when opening the shutter blade, only the second coil is excited by one phase to open the shutter blade. As described above, the shutter driving mechanism employing the step motor 1 described above switches between a fast operation of the rotor 2 when speed is required and an operation that emphasizes suppression of power consumption when speed is not required. Can do. Therefore, the driving mechanism can reduce power consumption while maintaining the shutter speed required for the camera. 7 and 8 exemplify the case where the diaphragm blade is driven as a sector together with the shutter blade, but it is of course possible to drive only the shutter blade. In FIG. 9, the left side is described as the conventional type. However, in the present driving mechanism, the conventional type can be driven as necessary. Further, in the power saving type on the right side of FIG. 9, the first coil is not energized, but it goes without saying that the reverse may be possible.
[0036]
The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment, and various modifications can be made within the scope of the gist of the present invention described in the claims.・ Change is possible.
[0037]
【The invention's effect】
As described above, according to the present invention, the current supply switching means can switch between the two-phase excitation case and the one-phase excitation case. It can be provided as a drive mechanism for a camera that can be used separately from the emphasis form. Such a camera drive mechanism can reduce power consumption by utilizing the time when the rotational speed of the rotor is not required.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a main part of a step motor according to an embodiment.
FIG. 2 is a diagram showing a case where the rotor of the step motor according to the embodiment is rotated by two-phase excitation.
FIG. 3 is a diagram showing a case where the rotor of the step motor according to the embodiment is rotated clockwise by one-phase excitation.
FIG. 4 is a diagram showing a case where the rotor of the step motor according to the embodiment is rotated counterclockwise by one-phase excitation.
FIG. 5 is a view showing a stator having a preferable shape for use in a step motor.
6A is a diagram schematically showing a state in which the step motor of FIG. 1 is arranged with respect to the shutter substrate in plan view. FIG. (B) is a view showing the movement locus CR of the engagement pin.
FIG. 7 is a view showing a state in which a photographing lens opening provided on a substrate is fully opened.
FIG. 8 is a view showing a state where a photographing lens aperture provided on a substrate is fully closed.
FIG. 9 is a diagram showing a relationship between a pulse waveform of a coil of a step motor for driving a shutter and an open / close state of a shutter blade.
[Explanation of symbols]
1 step motor 2 rotor 3 stator 4 first coil 5 second coil 11 first magnetic pole 12 second magnetic pole 13 third magnetic pole 25 current control circuit 60 first shutter blade 65 second shutter blade

Claims (4)

A rotor having four magnetic poles, a first magnetic pole excited by a first coil, a second magnetic pole excited by a second coil, and a third magnetic pole excited by the first and second coils Current supply switching for switching between the case of supplying the stator and the case of supplying a current to the first coil and the second coil and the case of supplying a current to one of the first coil and the second coil A step motor comprising means;
A sector that is moved by the step motor between a position for closing the imaging aperture formed on the substrate and a position for opening the imaging aperture;
The current supply switching means supplies current to the first coil and the second coil when the sector is in the closing position, and when the sector is in the opening position, the first coil and the second coil. A drive mechanism for a camera, wherein a current is supplied to one of the two coils. The rotor has a cylindrical shape, the stator has a U-shaped cross section, the stator is disposed so as to face the outer peripheral surface of the rotor, and the first magnetic pole and the The camera driving mechanism according to claim 1, wherein a second magnetic pole is set, and the third magnetic pole is set at a center position of the stator. The camera driving mechanism according to claim 1, wherein the sector includes a shutter blade. A rotor having four magnetic poles, a first magnetic pole excited by a first coil, a second magnetic pole excited by a second coil, and a third magnetic pole excited by the first and second coils A step motor driving method including a stator including:
The rotor is driven by switching between supplying a current to the first coil and the second coil and supplying a current to one of the first coil and the second coil. And a stepping motor driving method.

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