JP2003333773A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend the duration of a life by reducing the number of part items and assembling man-hours while reducing the size and weight of a brushless motor. <P>SOLUTION: The brushless motor comprises a stator 1 and a cylindrical rotor 2 for covering the stator. The stator 1 comprises a pair of plate-shaped stator pole pieces 11, a pair of annular stator coils 13 that are arranged in the pieces, and a bearing member 14 that externally fixes the pieces and the coils. The bearing member 14 is made of an iron-sintered metal and functions as a magnetic path, and of which the inside hole is a bearing hole 14d for rotatably supporting a rotating shaft 21. The cylindrical rotor 2 comprises an annular magnet 22 that surrounds a pole 11c of the plate-shaped stator pole piece 11 at a small interval, a cylindrical body 23 that supports the magnet at its internal peripheral surface, and the rotating shaft 21 that is fixed to the center of an end disc plate 23a via an eccentric spindle 6. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-sized motor that can be used as a small vibration motor, a fan motor, etc., and in particular, a small and lightweight brushless motor suitable for being used for such an application inside an electronic device or the like. Regarding

[0002]

2. Description of the Related Art In order to notify an incoming call in place of an acoustic alarm on a mobile phone or PHS, to notify a user of time with an electronic notebook or other mobile device, or to experience vibration in a game machine controller. For the purpose, a small vibration motor is widely used as a vibration source. In this type of conventional vibration motor, a semicircular eccentric weight is attached to the output shaft of a small motor with a brush, and vibration is generated by rotational movement of the centrifugal force generated by the eccentric weight.

Further, in precision electronic equipment and the like suitable for carrying, elements that dislike high temperatures are used, and a small fan for forcibly radiating those elements is often required. Needless to say, such a small fan is configured with a corresponding small motor as a drive source.

A small vibration motor as the vibration source,
A small motor such as a small fan motor as a blast source is required to have stable performance for a long period of time. Mobile phones, electronic organizers, and various mobile tools that use these small motors are required to be small and lightweight due to the convenience of mobile phones and design requirements. Furthermore, these small motors are required for the operation of such devices. It is an auxiliary part that plays an important role, and it is necessary to try to extend its service life.

For example, in the case of a vibration motor in which an eccentric weight is added to the rotary shaft of a small motor, an eccentric weight is added to the outside of both bearings in a rotary shaft supported by two conventional bearings. Therefore, the structure is such that the bearing near the eccentric weight is used as a fulcrum to generate vibration on the rotary shaft. This corresponds to simply connecting the eccentric weight to the rotating shaft originally designed to support the balanced load.

Therefore, an eccentric force is applied to the bearing farther from the eccentric weight, and the wear of the bearing portion is increased, so that the life of the motor is shortened as compared with the case where the bearing is used for a balanced load.
In order to prevent such shortening of the service life and to prolong the service life, it is necessary to employ stronger bearings and rotary shafts, which tends to increase manufacturing costs and weight.

[0007]

SUMMARY OF THE INVENTION In consideration of the above-mentioned problems of the prior art, the present invention provides a brushless motor which can reduce the number of parts and the number of assembling steps, can be made compact and lightweight, and can have a long life. The challenge is to provide.

[0008]

According to a first aspect of the present invention, an annular stator coil is arranged so that its own magnetic pole is inserted between the respective magnetic poles of the annular stator coil which rises from the respective end sides thereof and extends along the circumferential side thereof. A pair of plate-shaped stator pole pieces, the current supplied to the annular stator coil is controlled according to the rotational position of the cylindrical rotor, which will be described later. A stator configured to generate a moving magnetic field by changing the polarity, and a cylindrical rotor that surrounds the outer peripheral portions of the magnetic poles of the pair of plate-shaped stator pole pieces, and has a required inner peripheral surface. A cylindrical rotor whose portions are alternately magnetized in the circumferential direction with opposite polarities, and a bearing member that rotatably supports the rotating shaft of the cylindrical rotor, and a pair of plate-shaped fixing members that are mounted on the bearing member. Fixed part of the child magnetic pole piece, the annular stator coil, and the pair of plate-shaped stators The bearing member also functions as a yoke forming a part of in the magnetic circuit between the pole pieces, in a brushless motor configured.

Therefore, according to the brushless motor of the first aspect of the present invention, as described above, the bearing member literally functions as a bearing member and also functions as a fixing portion of the two plate-shaped stator pole pieces. Furthermore, since it functions as a yoke that forms a part of the magnetic circuit between the annular stator coil and the two plate-shaped stator pole pieces, the number of constituent parts is reduced by that amount, and as a matter of course, assembly is performed. The man-hour is also reduced,
As a result, miniaturization has become possible. Further, because of the structure, the bearing member can have a long contact area, and as a result, even if the bearing member is used as a motor for a vibration motor, abnormal wear such as uneven wear of the rotating shaft and the bearing is reduced. Therefore, the life can be extended.

Further, the annular stator coil (field coil)
Since a flat coil can be obtained by reducing the number of windings or the winding thickness of the coil, it is possible to form the plate-shaped stator pole pieces and the cylindrical rotor that surrounds them in a thin shape. And the size can be reduced.
Thus, as described above, not only the assembly man-hours are reduced by reducing the number of parts, but also the overall length is shortened to form an ultra-thin flat motor, which is incorporated into a small and lightweight precision electronic device suitable for carrying. Can be any suitable.

According to a second aspect of the present invention, in the brushless motor according to the first aspect of the present invention, the bearing member is made of an iron-based sintered metal.

Therefore, according to the brushless motor of the second aspect of the present invention, since the bearing member is made of the ferrous sintered metal, the bearing member can be impregnated with oil to be used as a good bearing member. It also effectively functions as a magnetic path coupled to the plate-shaped stator pole piece.

According to a third aspect of the present invention, in the brushless motor according to the first or second aspect of the present invention, a protrusion is formed on an inner surface of an eccentric weight fixed to the central axis of the cylindrical rotor, and the protrusion is This is configured as a vibration motor by engaging with a locking hole opened on the end face of the cylindrical rotor facing this.

Therefore, according to the brushless motor of the third aspect of the present invention, the eccentric weight can be easily and surely attached to the cylindrical rotor to form the vibration motor.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail based on examples with reference to the drawings.

<Embodiment 1> FIG. 1 is a side sectional view showing an example in which an eccentric weight is added to the brushless motor of Embodiment 1 to constitute a vibration motor, and FIG. 2 (a) shows two stators. FIG. 2B is a perspective view showing a combined structure of a plate-shaped stator pole piece and two annular stator coils, and FIG. 2B shows a bearing member that also serves as a fixing portion and a magnetic path of the two plate-shaped stator pole pieces. 2 is a perspective view of FIG.
(c) is a perspective view of two annular stator coils, Fig. 3 (a) is a vertical side view of two plate-shaped stator pole pieces combined in a facing state, and Fig. 3 (b) is two plates. 3C is a longitudinal sectional view of a bearing member that also serves as a fixed portion of a magnetic pole piece of a stator and a magnetic path. FIG. 3C is a side view showing a rotary shaft of a cylindrical rotor. It is a control circuit that controls the current flowing through the individual annular stator coils.

The brushless motor of the first embodiment is shown in FIG.
As shown in FIG. 3, the stator 1 and the cylindrical rotor 2 that is mounted on the stator 1 are configured.

As shown in FIGS. 1 and 2 (a) and 2 (b), the stator 1 has a pair of plate-shaped stator pole pieces 11 and 11 facing each other at their base portions 11b and 11b in an orthogonal state. And a pair of annular stator coils 13 and 13 arranged inside the insulating sheet 12 and the plate-shaped stator pole pieces 11 and 1.
1 and mounting holes 11a, 1 of the annular stator coils 13, 13
The bearing member 14 is inserted through 1a, 13a, and 13a, and is basically configured with a bearing member 14 that fixes the both members.

The plate-shaped stator pole piece 11 is made of a rectangular plate-shaped magnetic material having a central portion as a base portion 11b, and two end portions in the length direction thereof are bent so that two magnetic poles 11c face each other. 11c, and the mounting hole 11a is opened in the central portion of the base portion 11b as described above. The two facing magnetic poles 11c and 11c are processed so as to have a partial arc shape when viewed from the tip side. Further, the pair of plate-shaped stator pole pieces 11, 11 are
b, 11b with two annular stator coils 13,
After arranging 13 minutes, the outer surfaces of the annular stator coils 13 and 13 are made to face each other in an orthogonal state, and the mutual magnetic poles 11c and 11c are inserted between the mutually opposite magnetic poles 11c and 11c. Be located on the side.

As described above, the two annular stator coils 13 and 1 are provided between the pair of plate-shaped stator pole pieces 11 and 11.
In the case of inserting 3, as shown in FIG. 1, between the base portions 11b and 11b of the plate-shaped stator pole pieces 11 and the end faces of the annular stator coils 13 and 13 and the annular stator. It goes without saying that the insulating sheet 12 should be arranged between the inner periphery of the mounting hole 13a of the coil 13 and the outer periphery of the bearing member 14.

As shown in FIG. 2 (a), the mounting hole 11a opened in the base portion 11b of the plate-shaped stator pole piece 11 extends from the base portion 11b in the longitudinal direction of both magnetic poles 11c, 11c. A locking projection 11d is formed to project at an angle of 45 degrees, and the annular stator coils 13 and 1 are provided in the mounting hole 11a.
When the bearing member 14 is inserted together with the three mounting holes 13a, 13a, the bearing member 14 can be locked in the locking groove 14a formed along the lengthwise direction on the outer circumference thereof. As shown in FIGS. 1 and 2 (a), the pair of plate-shaped stator pole pieces 11 and 11 are made to face each other with their base portions 11b and 11b orthogonal to each other. Mutual locking protrusions 11d, 1 formed in the mounting holes 11a, 11a of the pieces 11, 11.
1d is located at the same angular position, and can be fitted and locked in the locking groove 14a of the bearing member 14.

As shown in FIGS. 1, 2 (a) and 2 (c), the annular stator coils 13 and 13 are provided with mounting holes 13a and 13a at the centers of the plate-shaped stator pole pieces 11 and 11, respectively. The annular stator coils 13 and 13 are literally a pair of annular coils formed by winding an insulated conductor with a mounting hole 13a having a large diameter corresponding to the thickness of the insulating sheet 12.
Is connected to a power source so that field currents flow in opposite directions to each other, and is switched so that only one of the field currents flows at an appropriate timing according to the rotational position of the cylindrical rotor 2. A moving magnetic field is formed.

As described above and as shown in FIGS. 1 and 2 (a), the annular stator coils 13 and 13 are arranged inside the pair of plate-shaped stator pole pieces 11 and 11 which face each other. Is arranged via the insulating sheet 12. As a mounting procedure, the bearing member 14 is exteriorly mounted via the insulating sheet 12, and then the pair of plate-shaped magnetic pole pieces 11, 11 are
As described above, the bases 11b, 11b are exteriorly faced while facing each other.

The bearing member 14 is made of a sintered metal formed mainly of iron powder, and is made of a material such as that shown in FIGS. 1, 2 (b) and 3 (b).
As shown in FIG. 5, the bearing body 14b has a cylindrical shape and a mounting collar 14c formed immediately before one end thereof, and the outer peripheral portion of the bearing body 14b has the annular stator coil 1
3, 13 and the pair of plate-shaped stators serving as fixing portions for fixing the magnetic pole pieces 11, 11, and the inner hole portion thereof constitutes a slide bearing for rotatably supporting the rotating shaft 21 of the cylindrical rotor 2. It is a hole 14d.

On the outer peripheral portion of the bearing main body 14b, as described above and as shown in FIGS. 1 and 2B, the plate-shaped stator pole pieces 11, 11 are attached along the length direction thereof. Hole 11a
A locking groove 14a for locking the locking projection 11d is formed. Further, at least the bearing hole portion 14d of the bearing member 14
Further, oil is impregnated in the portion adjacent thereto and the lubrication necessary for the rotation of the rotary shaft 21 is performed.

Therefore, the bearing member 14 functions as a bearing for rotatably supporting the rotary shaft 21, and at the same time, a fixing means for fixing the pair of plate-shaped stator pole pieces 11, 11 and the annular stator coils 13, 13. And further functions as a yoke forming a part of a magnetic circuit between the pair of annular stator coils 13 and 13 and the pair of plate-shaped stator pole pieces 11.

As shown in FIGS. 1, 1 (b) and 3 (b), the mounting flange 14c of the bearing member 14 projects in the circumferential direction immediately before one end of the bearing body 14b. As shown in FIG. 1, a metal base 3, a circuit board 4 and the like are fixedly attached thereto. The circuit board 4 is provided with an electronic component 5 for a control circuit, which will be described later, which is necessary for performing on / off control of the field current.

As shown in FIG. 1, the cylindrical rotor 2 has a pair of plate-shaped stator pole pieces 11, 11 of the stator 1.
Of the magnetic poles 11c, 11c ... With a minute gap, a cylindrical body 23 rotatably supporting the annular magnet 22 on its inner peripheral surface, and a central portion of the end disk portion 23a of the cylindrical body 23. The rotary shaft 21 is fixed via the eccentric weight 6.

The annular magnet 22 is continuously magnetized so that the inside thereof has N poles and S poles alternately at a predetermined pitch in the circumferential direction. The annular magnet 22 of this embodiment is obtained by kneading magnetic powder containing iron oxide as a main component with a plastic material or a rubber material, and rolling and molding in a magnetic field to adjust the balance.

The rotary shaft 21 is made by quenching a small-diameter steel material and performing finishing treatment such as polishing. As described above and shown in FIG. 1, the rotary shaft 21 is inserted into the bearing hole portion 14d of the bearing member 14, and its inner end is brought into contact with the inner end of the bearing hole portion 14d. As described above, the annular magnet 22 has the rotating shaft 21 whose inner end is the bearing hole portion 14
Even when it is inserted until it comes into contact with the inner end of d, the magnetic poles 11c, 11c of the plate-shaped stator magnetic pole pieces 11, 11 of the stator 1 are not completely in the facing state, but are slightly displaced in the front direction. Shall be kept.

As described above, the rotary shaft 21 is inserted into the bearing hole portion 14d of the bearing member 14 and is rotatably supported by the bearing hole portion 14d. It has not been. However, when a field current flows through the annular stator coils 13, 13, magnetic attraction is generated between the magnetic poles 11c, 11c ... Of the plate-like stator magnetic pole pieces 11, 11 and the annular magnet 22 of the cylindrical rotor 2. A force acts, whereby a thrust force acts in a direction in which the rotary shaft 21 of the cylindrical rotor 2 enters the bearing hole portion 14d of the bearing member 14, and the rotary shaft 21 deviates from the bearing hole portion 14d. Will be prevented.

The coupling between the end disc portion 23a of the cylindrical body 23 and the rotary shaft 21 is performed through the eccentric weight 6 as described above. As shown in FIG. 1, the eccentric weight 6 is formed by stacking a plurality of substantially semicircular support weight pieces 6a, 6a, ... In addition, by pressing the vicinity of the middle of the central portion and the outer peripheral portion from the outer surface side to the back surface side and projecting to the back surface side, the supporting weight pieces 6a, 6a ...
The protruding portion 6b of the split weight piece 6a located on the most back surface side is inserted into the coupling hole 23b opened at a corresponding position of the end disk portion 23a of the cylindrical body 23, and is caulked from the inside thereof. Combine and fix.

Therefore, the cylindrical rotor 2 has its cylindrical body 23.
After the eccentric weight 6 is attached to the end disc portion 23a of the above, the rotary shaft 21 attached via the eccentric weight 6 should be inserted into the bearing hole portion 14d of the bearing member 14.

The eccentric weight 6 has a rotating shaft 21 at the center thereof.
And the inner end side disc portion 23a of the cylindrical body 23 on the inner surface side.
It is attached to the rotary shaft 21.
Further, since it is in an eccentric state literally with respect to the end disc portion 23a and is in an unbalanced state, it acts as a vibration source when the rotary shaft 21 rotates.

A DC power source is connected to the annular stator coils 13 and 13 through a control circuit as shown in FIG. The pair of annular stator coils 13, 1
3 is the + side of the power source and transistors Tr1 and Tr2, respectively
Is connected in series with the collector of the cylindrical rotor 2, and the annular magnet 22 of the cylindrical rotor 2 is connected to the base of one of the transistors Tr1.
Is connected to the output of the magnetic detection element (Hall IC) H, and the collector-emitter of the transistor Tr1 becomes conductive or non-conductive due to the change in the voltage between the grounds thereof. The annular stator coil 13 connected to the collector is on / off controlled, and on the other hand, the collector-emitter of the other transistor Tr2 becomes conductive or non-conductive due to the change in the collector-emitter voltage of the transistor Tr1. As a result, the annular stator coil 13 connected to the collector is on / off controlled.

In FIG. 4, r1 is a limiting resistor for bias current of the magnetic detection element H, r2 is a limiting resistor for base current of the transistor Tr1, and r3 is a limiting resistor for base current of the transistor Tr2.

Therefore, the annular stator coils 13, 13 are
Depending on the rotational position of the annular magnet 22 arranged on the inner surface of the cylindrical body 23 of the cylindrical rotor 2, the collector-emitter of one of the corresponding transistors Tr1 or Tr2 becomes conductive, and the corresponding transistor Tr1 is turned on. Or Tr
A current will flow through it connected in series to the second collector.

That is, depending on the rotational position of the annular magnet 22, a field current flows in either of the annular stator coils 13 and 13, and the plate-shaped stator pole piece 1 which is mounted on the field current flows.
1 and 11 are excited. The magnetic poles 11c, 11c ... Of the two plate-shaped stator pole pieces 11, 11 are excited to have mutually opposite polarities, and the annular stator coils 13, 13 generate mutually opposite magnetic fields. Since the magnets are arranged so as to be generated, when the annular magnet 22 rotates, a current alternately flows through the annular stator coils 13 and 13 with it, and further, with this, the plate-shaped stator pole piece 11 , 11
The polarities of the magnetic poles 11c, 11c ...
As a result, a moving magnetic field is generated, and the annular magnet 22 is attracted and repulsed between the magnetized portion and the magnetic flux generated from the magnetic poles 11c, 11c of the plate-shaped stator magnetic pole pieces 11, 11 to generate torque. The cylindrical rotor 2 is generated and rotated, and the cylindrical rotor 2 including the cylindrical body 23 holding it is rotated accordingly.

Therefore, according to the brushless motor of the first embodiment, the bearing member 14 functions as a bearing that rotatably supports the rotary shaft 21 of the cylindrical rotor 2, and at the same time, the pair of plate-shaped fixed members are fixed. It also functions as a fixing means for fixing the child magnetic pole pieces 11, 11 and the annular stator coils 13, 13 and, in addition, the pair of annular stator coils 13, 13
And a function as a yoke that forms a part of the magnetic circuit between the pair of plate-shaped stator pole pieces 11 and 11, which reduces the number of parts and the number of assembling steps, and is small and lightweight while being long. It is possible to extend the life.

When the brushless motor of the first embodiment is connected to a DC power source, it is rotated as described above, thereby causing an eccentric rotary motion by the eccentric weight 6 attached to the cylindrical rotor 2, It goes without saying that it can generate the necessary vibration.

<Embodiment 2> FIG. 5 is a partially cutaway side sectional view showing an example in which a fan is attached to the cylindrical rotor of the brushless motor of Embodiment 2 to form a fan motor.

The brushless motor of the second embodiment is basically different only in that a fan 7 is attached instead of the eccentric weight 6 of the brushless motor of the first embodiment. There are some other differences, but they are all due to the fact that the fan 7 is attached instead of the eccentric weight 6.

Since the structure of the stator 1 side is exactly the same as that of the first embodiment, only the cylindrical rotor 2 side will be described. The fan 7 is attached to the outer periphery of the cylindrical body 23 that constitutes the cylindrical rotor 2. The fan 7 is supported by a cylindrical portion 7a attached to the outer periphery of the fan 7 and an end supporting disk 7b continuous to the end of the cylindrical portion 7a.
The fan 7 is attached to the outer periphery of the cylindrical rotor by coating a on the cylindrical body 23. Fan 7 to be attached
Number, shape, pitch, etc. of the brushless motor,
It can be determined in consideration of the purpose of use.

The rotary shaft 2 is provided in the center hole of the end supporting disk 7b.
1 is fixedly installed, and the rotary shaft 21 is rotatably inserted into the bearing hole 14d of the bearing member 14. Since it is not necessary to attach the eccentric weight 6 to the rotary shaft 21, it is shorter than that of the first embodiment. In addition, the cylindrical body 23 of the cylindrical rotor 2
Is coupled to the rotary shaft 21 via the cylindrical portion 7a supporting the fan 7 and the end supporting disc 7b as described above,
The end disc portion 23a is omitted.

On the inner circumference of the cylindrical body 23, the ring magnet 2 is provided.
Attach 2. The ring magnet 22 is exactly the same as that of the first embodiment and is attached in the same manner.

Therefore, the brushless motor of the second embodiment also uses the same bearing member 14 as that of the first embodiment. In the most important aspect, the brushless motor operates exactly like that of the first embodiment and has the same effect. .

Further, according to the brushless motor of the second embodiment, if this brushless motor is connected to a DC power source, it is rotated,
By this, the fan 7 attached to the cylindrical rotor 2
Needless to say, it is possible to generate the air blowing effect by.

<Third Embodiment> FIG. 6 is a front view of a stator of a brushless motor according to a third embodiment.

The brushless motor of the third embodiment is obtained by modifying the stator 1 of the first embodiment by one. In the brushless motor of the first embodiment, the pair of plate-shaped stator pole pieces 11, 11 are arranged so that their base portions 11b face each other in an orthogonal state. As shown in FIG. 5, the two are opposed to each other while being displaced from the orthogonal state by the angle α.

As a result, in the brushless motor of the third embodiment, it is possible to reliably specify the rotation direction and increase the starting torque. Except for this, the same operation as in Example 1 and the same effects are obtained.

[0051]

As described above, according to the brushless motor of the present invention, the bearing member literally functions as the bearing of the rotary shaft and also functions as the fixing portion of the pair of plate-shaped stator pole pieces. And, since the annular stator coil and the pair of plate-shaped stator pole pieces are configured to also serve as a yoke forming a part of the magnetic circuit between the pair of plate-shaped stator pole pieces, the number of component parts is reduced accordingly. Naturally, the number of assembling steps is also reduced, and as a result, it is possible to reduce the size. Further, because of the structure, the bearing member can have a long contact area, and as a result, even if the bearing member is used as a motor for a vibration motor, abnormal wear such as uneven wear of the rotating shaft and the bearing is reduced. Therefore, the life can be extended.

According to the second brushless motor of the present invention,
Since the bearing member is made of iron-based sintered metal,
It can be impregnated with oil to be used as a good bearing member, and can effectively function as a yoke that constitutes a part of the magnetic circuit.

According to the third brushless motor of the present invention,
The eccentric weight can be simply and surely attached to the cylindrical rotor to form the vibration motor.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an example in which an eccentric weight is added to the brushless motor of the first embodiment to constitute a vibration motor.

FIG. 2A is a perspective view showing a combined structure of two plate-shaped stator pole pieces and two annular stator coils in the stator. FIG. 3B is a perspective view of a bearing member that also serves as a fixing portion of two plate-shaped stator pole pieces and a magnetic path. (c) is a perspective view of two annular stator coils.

FIG. 3A is a vertical cross-sectional side view of two plate-shaped stator pole pieces combined in a facing state. FIG. 3B is a vertical cross-sectional view of a bearing member that also serves as a fixing portion and a magnetic path of two plate-shaped stator pole pieces. (c) is a side view showing the rotation axis of the cylindrical rotor.

FIG. 4 is a control circuit for controlling a current flowing through two annular stator coils of the brushless motor of the first embodiment.

FIG. 5 is a partially cutaway side sectional view showing an example in which a fan is attached to a cylindrical rotor of a brushless motor of a second embodiment to form a fan motor.

FIG. 6 is a front view of a stator of a brushless motor according to a third embodiment.

[Explanation of symbols]

1 stator 11 Plate-shaped stator pole pieces 11a Plate-shaped stator pole piece mounting hole 11b Base of plate-shaped stator pole piece 11c Magnetic pole of plate-shaped stator pole piece 11d locking protrusion 12 Insulation sheet 13 Annular stator coil 13a Mounting hole for annular stator coil 14 Bearing member 14a locking groove 14b Bearing body 14c Mounting collar 14d bearing hole 2 Cylindrical rotor 21 rotation axis 22 annular magnet 23 cylindrical body 23a End disk portion of cylindrical body 23b A coupling hole opened in the end disc portion of the cylindrical body 3 base 4 circuit board 5 electronic components 6 Eccentric weight 6a Split weight piece 6b protrusion 7 fans 7a Cylindrical part 7b End support disc Tr1 and Tr2 transistors H Magnetic detection element (Hall IC) r1 Bias current limiting resistance of magnetic detection element r2, r3 base current limiting resistor of transistor

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5D107 AA09 AA11 AA12 BB08 CC09                       DD09                 5H002 AA08 AB06 AC08 AE08                 5H607 AA11 AA12 BB01 BB07 BB14                       BB17 CC03 DD03 DD08 DD17                       EE40 FF04 FF12 GG01 GG09                       JJ02 KK03                 5H621 BB09 JK19

Claims (3)

[Claims] 1. An annular stator coil and a pair of plate-shaped stator pole pieces arranged so that their own magnetic poles are inserted between respective magnetic poles of the annular stator coil which rise from the respective end sides and extend along the circumferential side of the annular stator coil. The current supplied to the annular stator coil is controlled according to the rotational position of the cylindrical rotor, which will be described later, and changes the polarities of the magnetic poles of the pair of plate-shaped stator magnetic pole pieces to generate a moving magnetic field. And a cylindrical rotor that surrounds the outer peripheral portion of the magnetic poles of the pair of plate-shaped stator magnetic pole pieces, and the required portions of the inner peripheral surface thereof have alternating polarities in the circumferential direction. A cylindrical rotor that is magnetized, a bearing member that rotatably supports the rotating shaft of the cylindrical rotor, and a fixed portion of a pair of plate-shaped stator pole pieces that is mounted on the bearing member, and the annular member. Of the magnetic circuit between the stator coil and the pair of plate-shaped stator pole pieces The bearing member also functions as a yoke that forms a part, in construction the brushless motor. 2. The brushless motor according to claim 1, wherein the bearing member is made of an iron-based sintered metal. 3. A projection is formed on the inner surface of an eccentric weight fixedly mounted on the central axis of the cylindrical rotor, and the projection is formed into a locking hole opened on an end surface of the cylindrical rotor facing the eccentric weight. The brushless motor according to claim 1 or 2, wherein the brushless motor is engaged and configured as a vibration motor.