JP2002034222A - Motor utilizing magnetic flux's phenomenon of convergence - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor that allows the attainment of high efficiency and is satisfactory in starting capability. SOLUTION: The motor includes a rotor 10 provided with disks 10c, made of a substantially circular plate-like magnetic material and having a plurality of projections 10a and permanent magnets 20 sandwiched between the disks, and bypassing portions Mp as passages for magnetic flux are formed between the disks 10c. A plurality of electromagnets 30, placed between the rims of the disks 10c, are supplied with exciting current from a controller 50 at specified timings, so that the polarity of the ends thereof on the side opposite the disks 10c is different from the polarity from the permanent magnets 20. When there is no passage of current, the magnetic flux of the permanent magnets 20 circulates through the bypassing portions Mp in a closed state, and the circulation of magnetic flux will not occur between them and the surrounding electromagnets. When excitation current is supplied to any of the electromagnets, however, magnetic flux entering and exiting the magnetic poles of the permanent magnets 20 is attracted into the electromagnets which are excited with different polarities and magnetic attraction force is produced between them to produce a rotational driving force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor using a magnetic flux of a permanent magnet, and more particularly to a method of converging a magnetic flux generated inside a magnetic material mounted on the permanent magnet only in a direction effective for generating a rotational driving force. The present invention relates to an electric motor capable of achieving high efficiency and high torque.

[0002]

2. Description of the Related Art Conventionally, mechanical output of electric energy,
For example, various electric motors have been developed as conversion systems capable of extracting torque. In these conventional motors, an electromagnet is used for one or both of a stator and a rotor, and the electromagnet generates a rotating magnetic field to follow the rotor (for example, an induction motor) or a permanent magnet. A rotor provided so as to be capable of polarity reversal control in a stator magnetic field is rotatably arranged, and a rotating force is obtained by interaction of magnetic flux between the rotor and the stator (for example, a general DC motor). is there.

[0003] For such a conventional motor, various attempts have been made to increase the energy conversion efficiency by using a magnetic flux generated from a permanent magnet. The inventors have
In particular, by appropriately controlling the distribution of the magnetic flux generated by the permanent magnet, the magnetic force acting against the output torque is reduced as much as possible, thereby increasing the output torque and reducing the electromagnetic energy to mechanical energy. In order to achieve higher conversion efficiency, prototypes of torque generators with various configurations have been developed.

[0004] For example, Japanese Patent Application Laid-Open No.
No. 9559 proposes a power generating device capable of increasing energy conversion efficiency by adding a permanent magnet to a rotor. In the power generator according to this proposal, a ring-shaped permanent magnet magnetized in the axial direction is disposed on both ends in the axial direction of the rotatable output shaft that is rotatably mounted, and is closely attached to the ring-shaped permanent magnet. Then, plate-shaped magnetic bodies provided with three notches and magnetic teeth alternately on the outer periphery are fixed to be in phase with each other. The permanent magnet and the plate-shaped magnetic body are coaxial with the rotation output shaft and constitute a rotor that rotates together with the rotation output shaft. With such a configuration, in the non-energized state,
The electromagnet facing the magnetic teeth of the plate-shaped magnetic body is simply a magnetic body in the magnetic field of the permanent magnet, and the rotor is stationary. From this state, when the electromagnets located at the boundary between the notch of the plate-shaped magnetic body and the magnetic teeth are simultaneously excited, the magnetic field of the permanent magnet and the magnetic field of the electromagnet act on each other, and the magnetic flux passing through the plate-shaped magnetic body is generated. It is instantaneously converged on the electromagnet side. This allows
The rotor is attracted to the excited electromagnet side and receives a rotating torque in a direction to increase the width of the magnetic flux. Then, by sequentially exciting the electromagnets positioned in the rotation direction of the magnetic tooth portion, the rotation of the rotor can be maintained. In addition, at this time, there is almost no magnetic flux behind the rotation direction of each magnetic flux, so to say, a blank area of the magnetic flux occurs, so that the magnetic attraction force from the rear non-exciting electromagnet that hinders the rotational movement of the rotor is reduced. Is to be reduced as much as possible.

Further, as a device developed by the present inventors for the same purpose, there is a torque generating device described in Japanese Patent Application Laid-Open No. 10-32967. In this device, a plurality of radial rotor salient poles each having a rotor salient pole made up of a base of a permanent magnet and a magnetic member are provided around the outer periphery of a substantially disk-shaped rotor core. These rotor salient poles are intended to obtain torque by sequentially exciting the stator salient poles, each of which is an electromagnet, by sequentially exciting them. At this time, the magnetic flux passing through the magnetic material forming the rotor salient poles is converged toward the excited stator salient poles in the forward direction of rotation, and the non-excited stator located in the rear of the respective rotor salient poles in the rotational direction. It was considered that magnetic attraction that hindered rotation hardly acts between the salient poles.

[0006]

However, when the performance such as the energy conversion efficiency and the generated torque was verified through various prototypes including the above-described apparatus, a certain improvement in performance was recognized, but the performance of the magnetic member was not improved. It has been found that there is a possibility that the magnetic flux does not converge as expected, and that sufficient efficiency cannot be improved in some cases. This tendency is considered more remarkable in the case of the latter torque generator in which the volume of each magnetic salient pole is small.

Further, since a permanent magnet is incorporated in the rotor, when no electromagnet is energized, an attractive force acts between each permanent magnet and a specific electromagnet located close to the rotor. While the rotor is in a strongly restrained state, at the time of starting, even if a predetermined electromagnet is supplied with a current to excite it, the convergence of the magnetic flux as described above is insufficient. Can not release the restraint state,
It was also confirmed that the starting of the rotor may be difficult.

The present invention has been made to solve the problems found in the development process as described above while paying attention to the importance of using a combination of a permanent magnet and a magnetic material, which has been newly clarified. An object of the present invention is to provide a permanent magnet electric motor which can obtain high efficiency and high torque by effectively utilizing the magnetic energy of a permanent magnet and has excellent startability.

[0009]

In order to achieve the above object, an electric motor according to the present invention comprises at least one pair of a magnetic body and a plurality of radial projections provided along an outer peripheral edge thereof. An output member, magnetizing means arranged to magnetize the output members with different polarities from each other, and arranged so as to be substantially spanned between respective outer peripheral edges of the output member, one end of which is provided. The other end portion is disposed at an outer peripheral edge of the one output member at intervals along the outer peripheral edge of the other output member, and each of them has a magnetic interaction with each of the output members. A plurality of electromagnets, at least one magnetic flux bypass unit connected between the output members, and a support unit that supports the output member so as to be rotatable in a circumferential direction inside the plurality of electromagnets; ,
Each of the electromagnets facing each outer peripheral edge of the output member has a different polarity from the output member side polarity provided by the magnetizing means, so that the end facing each output member has a different polarity. And an exciting current supplying means for supplying an exciting current at a predetermined timing, and when no exciting current is supplied to any of the electromagnets, the magnetic flux from each magnetic pole of the magnetizing means connects between the output members. Closed through the magnetic flux bypass means, no magnetic flux is magnetized between the surrounding electromagnets, and when an exciting current is supplied to any electromagnet, the magnetic flux from each magnetic pole of the magnetizing means is It is characterized in that it is drawn into an electromagnet excited to different polarities, generates a magnetic attraction force between the two, and generates a rotational driving force.

Preferably, each of the output members is made of a substantially disk-shaped magnetic material, and is fixedly juxtaposed to the support member so as to sandwich the magnetizing means formed in a substantially cylindrical shape. And a sleeve made of a substantially cylindrical magnetic material disposed along the outer peripheral edge of each output member so as to surround the output member and the magnetized member. Are formed in the sleeve, and the sleeve is provided with rectangular window-shaped openings each having a predetermined width at intervals in the direction of the outer peripheral side thereof, and the sleeve is sandwiched between the openings. A configuration is adopted in which the sleeve peripheral side portion is used as the magnetic flux bypass means.

The magnetizing means may be a permanent magnet or an electromagnet whose magnetic force can be adjusted.

[0012] Further, each of the electromagnets is sequentially supplied with a predetermined current by the excitation current supply means so as to be excited so that each of the electromagnets continuously attracts a protrusion disposed on the periphery of the output member. And

According to the electric motor of the present invention having the above-described configuration, when none of the electromagnets is excited, the magnetic flux entering and exiting the magnetic pole of the magnetizing means becomes (one magnetic pole of the magnetizing means) → ( Magnetization is performed in a path of (one output member) → (magnetic flux bypass means) → (the other output member) → (the other magnetic pole of the magnetizing means). That is, the magnetic flux entering and exiting the magnetizing means constitutes a closed magnetic circuit through the output member and the magnetic flux bypass means connected between them, and the non-excited electromagnet close to the outer peripheral edge of the output member No magnetic interaction occurs between them.

However, when a current is supplied to any of the electromagnets from the exciting current supply means and the magnet is excited, the magnetic flux from the magnetizing means, which has been closed through the output member and the magnetic flux bypass means, is released, and each output magnet is released. In the member, it sufficiently converges in each region connecting between the excited electromagnet and the magnetizing means. The output member can be continuously rotated by sequentially switching the exciting electromagnet in the rotation direction according to the rotation of the output member. That is, in the present invention, by providing the magnetic flux bypass means, while the electromagnet is not energized, the magnetic flux from the magnetizing means does not generate any magnetic force that restrains the output member with respect to the electromagnet, Once a predetermined electromagnet is energized and excited, the closed magnetic flux passing through the magnetic flux bypass means is immediately opened and the magnetic flux converges inside the output member as described above, and the magnetic flux generates a driving force. Concentrate on the electromagnet you are trying to do.

Further, since the magnetized member is disposed between the output members, the magnetic flux generated by the magnetized member can be used by being superimposed on the magnetic flux generated from the exciting electromagnet, so that the same rotational torque can be obtained. In this case, the required input power is greatly reduced.

[0016]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a side sectional view schematically showing a schematic configuration of an electric motor according to an embodiment of the present invention. In this figure, in order to clarify the basic configuration and operation of the present apparatus, parts that are not essential to the description of the present invention, such as the housing and the frame of the apparatus, are omitted as appropriate. I have.

As shown in FIG. 1, the electric motor according to the present embodiment mainly includes a rotor 10 for generating a rotational driving force, and a plurality of electromagnets 30 arranged so as to surround the rotor. The rotor 10 includes a pair of rotor disks 10c, a rotating shaft 40 for firmly contacting the disks 10c, and a substantially cylindrical permanent magnet 20 interposed between the two disks 10c so as to surround the rotating shaft 40. ,
A sleeve 10b provided so as to be fitted on the outer periphery of the disk 10c. The sleeve 10b and the disk 10c are formed of a magnetic material that allows a magnetic flux to pass. At end portions of the outer peripheral side of the sleeve 10b corresponding to the periphery of each disk 10c, four projections 10a each having a central angle of 60 ° are provided at regular intervals in the radial direction so as to surround the disk 10c. The protrusion 10a may be provided integrally with the sleeve 10b, may be provided separately from the sleeve 10b, or provided integrally with the disk 10c, as described below with reference to the embodiment of the present application. Various configurations, such as a configuration, can be adopted as necessary. FIG. 2 is a schematic perspective view of the rotor 10.

FIG. 3 shows a plan view and a side sectional view of the sleeve 10b in the present embodiment. The sleeve 10b is formed in a substantially thin cylindrical shape, and four openings W are provided at equal intervals on the outer peripheral side. In other words, four rectangular windows are formed on the outer peripheral side of the sleeve 10b at a central angle of 30 ° and open over the entire longitudinal length between the disks 10c. The portion sandwiched between the adjacent openings W is left so as to constitute a bypass Mp as magnetic flux bypass means. The shape and number of the opening W and the bypass Mp may be determined in consideration of various conditions such as the density of the magnetic flux for bypassing this portion and the magnetic flux emitted by the electromagnet 30 when energized.

The two disks 10c, 10c of the rotor 10
A plurality of electromagnets 30 extend at predetermined intervals so as to straddle between the outer peripheral portions of c. Each of the electromagnets 30 is formed by winding an exciting coil 36 around an intermediate portion of a substantially U-shaped core, and both ends 32 and 34 of the core project from the sleeve 10b of the rotor 10, respectively. Projection 1
0a is disposed so as to be close to and opposed to 0a. In the present embodiment, as described later with respect to the operation, 1
Two electromagnets 30 are arranged side by side so as to surround the rotor 10 at a pitch of 30 °. The rotating shaft 40 is supported by a bearing (not shown) so that the rotor 10 is rotatable inside the electromagnet 30 arranged in a ring.

As described above, in the rotor 10, between the two disks 10c arranged in parallel,
A permanent magnet 20 is provided. In this embodiment, the left disk 10c side in the figure is fixedly connected to the south pole so as to be located substantially coaxially with the center axis of the disk-shaped disk 10c. Of course, the arrangement of the magnetic poles may be opposite to that of the present embodiment, and is only relative.
In this embodiment, each end of the permanent magnet 20 and the disk 10c of the rotor 10 made of a magnetic material are configured to be in close contact with each other as separate members. It may be configured as an integral permanent magnet formed in a piece shape.

The control device 50 is connected to an appropriate power supply and controls the coils 3 provided on the twelve electromagnets 30 respectively.
6, which sequentially supplies an exciting output current to the motor 6, and generally includes a current switching device or element such as a relay, a transistor, or a thyristor, and a control circuit for controlling ON / OFF of the switching element or the like. . The control device 50 appropriately rectifies the power supply current and supplies the power supply current to each coil 36 as a signal having a predetermined output frequency and output current. In the electric motor according to the present invention, since the rotor 10 is basically driven synchronously with the sequential excitation control of the electromagnets 30, an open loop configuration may be used from the viewpoint of drive control. However, in order to detect the rotation angle of the rotor 10, the rotor 10 may be appropriately used by using various existing sensors such as an optical sensor or a rotary encoder combined with a light shielding plate (not shown) having a predetermined notch shape. Ten speed controls can be performed. In the present embodiment, a rotation sensor 60 for detecting the rotation angle of the rotor 10 is provided, and its output signal is
It is input to a control circuit of the control device 50 and is used as a trigger signal for controlling on / off of the current switching element and the like according to the rotation angle of the rotor 10, for example.

Next, the operation of the electric motor according to the embodiment of the present invention having the above configuration will be described with reference to FIGS. Note that, in these figures, the hatched portions schematically show the regions where the magnetic flux from the permanent magnet 20 or the excited electromagnet 30 is distributed. First, FIG. 4 shows a state in which no exciting current is supplied from the control device 50 to the coil 36 of any of the electromagnets 30 and none of the electromagnets 30 is excited, that is, a power-off state. In this state, the magnetic flux emitted from the N pole of the permanent magnet 20 is magnetized to the opposite S pole via the bypass portion Mp provided on the sleeve 10b of the rotor 10.
Therefore, the magnetic flux entering and exiting the permanent magnet 20 is generated by the bypass portion M of the sleeve 10 b provided in the rotor 10.
The non-excited electromagnet 30 disposed around the rotor 10 because it is confined in the rotor 10 through the p
No magnetic interaction between them. That is, in this state, the rotor 10 can freely rotate with the rotation shaft 40 as a support shaft, and no restraining force that adversely affects the startability is applied.

Next, as shown in FIG. 5, out of the twelve electromagnets 30, four of the electromagnets 30a, 30d, 30g, and 30j are connected to the control device 50.
To excite the magnetic poles of the electromagnets 30 so that the magnetic poles of the electromagnets 30 have different polarities from the magnetic poles of the permanent magnets 20 on the rotor 10 facing each other. At this time, in the non-energized state shown in FIG. 4, the magnetic flux that has been magnetized from the N pole of the permanent magnet 20 to the S pole through the bypass portion Mp provided on the sleeve 10 b of the rotor 10 has different magnetic poles. The electromagnets 30a, 30d, 30g, and 30j, which are excited to have polarities, converge, and a rotational torque acts on the rotor 10 clockwise by the magnetic attraction. (Indicated by thick arrows in the drawings. Hereinafter, the same applies to FIGS. 6 and 7.) Before the start, the magnetic flux entering and exiting the permanent magnet 20 is confined in the rotor 10 as described above.
When an exciting current is supplied to a predetermined electromagnet 30 at the time of starting, the magnetic flux is immediately converged on each magnetic pole of the excited electromagnet 30, and a magnetic attractive force acts on the rotor 10, thus impairing the startability of the rotor 10. Such a magnetic flux behavior does not occur.

FIG. 6 shows the rotor 1 following the state of FIG.
0 indicates a state of rotating clockwise while receiving a magnetic attraction force from the electromagnet 30. The convergence state of the magnetic flux in each disk 10c is determined by the magnetic poles of the permanent magnet 20 and the ends 32a, 32d, 32g of the electromagnet 30 being excited.
The state shown in FIG. 5 is the same as the state shown in FIG. 5 in that the projections 10a of the rotor 10 are located in front of the excitation direction. Each end 32a, 32d, 3 of the electromagnet 30
Only the magnetic attraction force from 2g, 32j and 34a, 34d, 34g, 34j is received, and there is no magnetic interaction with other non-exciting electromagnets 30c or the like that hinders rotation. In other words, after starting, the end 3 of each electromagnet 30 in the non-excited state until the state shown in FIG. 6 is reached.
The inside of the magnetic body of the rotor 10 facing the portions 2 and 34 is a blank area (a portion other than the hatched portion in the illustrated rotor 10) in which there is substantially no magnetic flux. From this, it is possible to improve the efficiency as well as the startability as described above. However, in the state shown in FIG. 6, since the end of each exciting electromagnet 30 and the protrusion 10a of the rotor 10 have reached the position where they are radially opposed, the magnetic attraction force in this state acts exclusively in the radial direction. It can be seen that it cannot contribute to the rotation drive of the rotor 10.

Here, as shown in FIG. 7, the non-excited electromagnets 30b, 30e, and 30h whose front edges in the rotational direction of the respective protrusions 10a of the rotor 10 are adjacent to the respective exciting electromagnets in the rotational direction. , 30k, the electromagnet 30 which has been excited until then
a, 30d, 30g, and 30j, stopping supply of current to the adjacent electromagnet 30 which has been non-excited until then.
A current is supplied to b, 30e, 30h, and 30k to excite them. This state is equivalent to the initial state shown in FIG. 5, and each rotor projection 10a is provided with the ends 32b, 32e, and 32 of the exciting electromagnet positioned forward in the clockwise direction.
h, 32k, and 34b, 34e, 34h, and 34k receive magnetic attraction by the magnetic flux converging between the magnetic poles of the permanent magnet 20 and continuously generate clockwise rotation torque. At this time, the behavior of the magnetic flux in the disk 10c is, as described with reference to FIGS.
Each magnetic pole of the permanent magnet 20 and the ends 32b, 32e, 32h, 32k, and 34b, 34b, and 3 of the newly excited electromagnet 30
4e, 34h, 34k, the magnetic flux converged and demagnetized to the non-excited electromagnets 30a, 30d, 30g, 30j disappears. Hereinafter, each of the electromagnets 3 is controlled by the control device 50.
By supplying the exciting current to 0 in the above-described procedure, the rotor 10 can continuously generate a rotating torque.

In the embodiment of the present invention described above, when the rotation speed of the rotor 10 is controlled, each of the electromagnets 3
The timing of switching the exciting current to 0 is determined by the number of electromagnets 30 arranged around the rotor 10, that is, the number n of poles on the stator side, and needs to be switched every (360 / n) ゜. Therefore, in this embodiment, since the number of poles on the stator side is n = 12, (360/12) =
The electromagnet 30 to be excited may be switched every 30 °. The direction in which the electromagnet 30 to be excited is switched may be determined according to a desired rotation direction.

In the above description, the exciting current is switched when the front end in the rotation direction of the protrusion 10a of the rotor 10 reaches a position close to each non-exciting electromagnet in front of the exciting electromagnet. Had a configuration. However, more strictly, a method of sequentially analyzing the change in the magnetic flux distribution when the rotor 10 rotates by using the finite element method is adopted, or the output characteristic is changed using the excitation switching timing for the electromagnet 30 as a parameter. By performing measurement comparison, it is possible to find not only an increase in output torque and an improvement in energy conversion efficiency, but also an optimum excitation current switching timing in consideration of other factors such as torque fluctuation suppression. Then, the setting condition of the sensor may be adjusted so that the output signal of the rotation sensor 60 for detecting the rotation angle of the rotor 10 satisfies the optimization condition.

[0028]

As described above in detail, according to the electric motor of the present invention having the above-described structure, the magnetic flux entering and exiting the magnetizing means in the non-energized state is connected to the output member and the output member. Since the magnet is closed in a closed state without any magnetic interaction with the electromagnet provided around the output member via the magnetic flux bypass means, the output member can freely rotate without receiving any restraining force. It is in a movable state. Then, if an exciting current is supplied to a predetermined one of the electromagnets to excite it, the magnetic flux from the magnetizing means, which has been magnetized in the closed state, is immediately converged on the newly excited electromagnet. Thus, the starting can be performed smoothly by the magnetic attraction force received from the exciting electromagnet.

Further, the output member receives only the magnetic attraction force from the exciting electromagnet, and no magnetic force that hinders rotation due to the convergence phenomenon of the magnetic flux acts between the output member and other non-exciting electromagnets. As a result, the output efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a configuration of an electric motor according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of a rotor of the electric motor according to the embodiment of the present invention.

FIG. 3 is a view showing a sleeve used for a rotor of the electric motor according to one embodiment of the present invention.

FIG. 4 is a first diagram illustrating an operation of the electric motor according to the embodiment of the present invention.

FIG. 5 is a second view showing the operation of the electric motor according to the embodiment of the present invention.

FIG. 6 is a third diagram showing the operation of the electric motor according to the embodiment of the present invention.

FIG. 7 is a fourth diagram illustrating the operation of the electric motor according to the embodiment of the present invention;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Rotor 10a Protrusion part (of rotor 10) 10b Sleeve (of rotor 10) 10c Rotor disk (output member) 20 Permanent magnet (magnetization means) 30 Electromagnet 40 Rotary shaft (support means) 50 Excitation control device (excitation current control means) Mp bypass part (magnetic flux bypass means) W opening part (of sleeve 10b)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H002 AA02 AA03 AB07 AC06 AE06 AE07 AE08 5H621 BB01 BB02 GA01 GA04 GA16 GA17 GB14 HH01 HH09 JK02 JK05 5H622 AA03 CA02 CB04 CB05 CB06 PP01 PP03 PP11 PP16

Claims (5)

[Claims] At least one pair of output members formed of a magnetic material and having a plurality of radial projections along an outer peripheral edge thereof, and a magnetization disposed so as to magnetize the output members with mutually different polarities. Means, and is disposed so as to be substantially spanned between the respective outer peripheral edges of the output member, one end of which is disposed on the outer peripheral edge of the one output member, and the other end of which is the outer peripheral edge of the other output member. A plurality of electromagnets that are arranged at intervals along and are adapted to magnetically interact with the output members, and at least one magnetic flux bypass means connected between the output members. A supporting means for supporting the output member rotatably in the circumferential direction inside the plurality of electromagnets; and each of the electromagnets facing each outer peripheral edge of the output member has a respective output. Facing the member Excitation current supply means for supplying an excitation current to each electromagnet at a predetermined timing so that the section has a different polarity from the output member side polarity provided by the magnetizing means, and the excitation current is supplied to any of the electromagnets. In the non-rotating state, the magnetic flux from each magnetic pole of the magnetizing means is closed through the magnetic flux bypass means connecting between the output members, and no magnetic flux is generated between the magnetic members and surrounding electromagnets. When an exciting current is supplied to any one of the electromagnets, the magnetic flux from each magnetic pole of the magnetizing means is drawn into the electromagnets excited to different polarities to generate a magnetic attraction force between the two to generate a rotational driving force. 2. The output member is made of a substantially disk-shaped magnetic material, and is fixedly juxtaposed to the support member so as to sandwich the magnetizing means formed in a substantially cylindrical shape. A sleeve made of a substantially cylindrical magnetic material is provided along the outer peripheral edge of each output member so as to surround the output member and the magnetized member, and a predetermined number of sleeves are provided on both outer peripheral edges in the axial direction of the sleeve. Radial projections are formed, and the sleeve is provided with rectangular window-shaped openings each having a predetermined width at an interval in the direction of the outer peripheral side thereof, and the sleeve is sandwiched between the openings. The electric motor according to claim 1, wherein a peripheral side portion of the sleeve is the magnetic flux bypass unit. 3. The magnetizing means is a permanent magnet.
Or the electric motor according to 2. 4. The electric motor according to claim 1, wherein said magnetizing means includes an electromagnet configured to adjust its magnetic force. 5. A method according to claim 1, wherein each of said electromagnets is supplied with a predetermined current by said excitation current supply means so as to be successively attracted to a projection disposed on a peripheral edge of said output member, and is excited. Item 5. The electric motor according to items 1 to 4.