JPH06284668A - Brushless motor - Google Patents

Abstract

PURPOSE:To facilitate manufacture and to reduce cogging while employing a rotor magnet composed of segment magnets by filling the gaps between segment magnets arranged annularly with a magnetic resin material thereby forming the rotor magnet. CONSTITUTION:The brushless motor comprises a stator 6 and a rotor magnet 8 rotary supported coaxially with the stator 6. In the rotor magnet 8, segment magnets 36 are arranged annularly through predetermined gaps 37 filled with a magnetic resin material. Since the segment magnet 36 is formed integrally, it can be formed accurately without requiring any sticking work. Furthermore, since the gaps 37 are filled with magnetic resin, flux from the segment magnet 36 does not diverge and thereby cogging is suppressed between the rotor magnet 8 and the stator 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a small DC brushless motor having an output of 100 watts or less.

[0002]

2. Description of the Related Art A small direct current motor mounted on an office automation equipment such as a dry copying machine or a small printer comprises a stator fixed to a bracket and a rotor opposed to the stator and coaxially rotatably supported. ing. On the rotor, a rotor magnet magnetized with a required number of magnetic poles is fixed to the yoke of the rotor. Then, when the required electric power is applied to the stator, the rotor is rotationally driven by the electromagnetic action of the stator and the rotor magnet.

As the rotor magnet, a magnet made of a ferrite material formed in a segment shape is usually used. These are arranged and fixed in a ring shape along the yoke of the rotor for the required number of sheets, whereby the required number of magnetic poles is obtained.

[0004]

However, in the brushless motor having such a structure, since the segment magnet is used for the rotor, the following problems occur in forming the rotor magnet. That is, it is necessary to attach segment magnets in an annular shape along the yoke of the rotor. At this time, in order to evenly dispose at a constant interval in the circumferential direction, it has to be performed accurately by a positioning jig or the like, and the work is complicated.

Further, a gap is not a little generated between the adjacent magnets, and the presence of this gap portion promotes an increase in reluctance torque with the stator, resulting in an increase in cogging and a cause of uneven rotation. Was there.

Further, in a brushless motor, an index magnet for detecting rotation and FG (frequency power generation)
In order to integrally attach a multi-pole magnet or the like for a rotor magnet to the rotor magnet, it is necessary to further fix and position the magnet.

The present invention has been made in view of the above problems existing in the prior art. The first problem is that a rotor magnet composed of segment magnets is used. It is an object of the present invention to provide a brushless motor which is easy to manufacture while using and can reduce cogging. Secondly, another magnet for rotation detection and FG detection signal generation
A brushless motor that can be easily and accurately provided on a rotor magnet.

[0008]

To achieve the above object, the first means in the brushless motor of the present invention is
A brushless motor comprising a stator and a rotor magnet rotatably supported coaxially with the stator; the rotor magnet comprises segment magnets annularly arranged with a predetermined gap in the circumferential direction. The gap is formed by interposing a magnetic resin material.

As a second means, the magnetic resin material forming portion is provided at an end portion in the axial direction of the rotor magnet, and the resin material forming portion has an N pole and an S pole. There is provided a brushless motor in which the magnetic poles are alternately magnetized in different directions or required magnetic poles are magnetized.

[0010]

According to the first means of the brushless motor according to the present invention, the segment magnets arranged annularly in the circumferential direction in the rotor magnet are integrally formed of a magnetic resin material. For this reason, it is possible to form and arrange the segment magnets with high precision without the need for attaching the individual segment magnets. A magnetic resin material is interposed between the adjacent segment magnets, so that the magnetic flux from each segment magnet is closed and does not diverge. This reduces cogging caused by the rotor magnet and the stator.

According to the second means, since the magnetic resin material forming portion is provided at the end portion of the rotor magnet in the axial direction, a predetermined magnetic pole or a required number of magnetic poles is provided in the resin material forming portion. Can be magnetized. Therefore, it is not necessary to specially attach such a magnetizing magnet and to position it. For this reason, it is possible to easily and accurately magnetize without the need for additional work.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a brushless motor according to the present invention will be described with reference to FIGS. First, FIGS. 1 to 3 show, for example, a brushless motor that rotationally drives a drum of a laser printer, FIG. 1 is a sectional view showing the whole thereof, and FIGS. 2 and 3 are perspective views developed in the axial direction. 1 to 3, the member 3 is a fixed frame that is attached to an apparatus (not shown), and a thin steel plate is used. Tongue-shaped cut-and-raised parts 22 are formed at four corners of the fixed frame 3 by plastic working, and the cut-and-raised parts 22 are fixed to the device through holes 43 formed therein. The cut-and-raised portion 22 substantially increases the wall thickness for mounting the fixed frame 3.

A cylindrical portion 5 is fixed to the fixed frame 3. The cylindrical portion 5 is made of aluminum, brass, or the like. A flange portion 11 protruding outward is provided on the outer peripheral portion of the cylindrical portion 5.
Are provided integrally. The fixed frame 3 is externally fitted to the side surface of the collar portion 11, is caulked, and is fixed integrally. The collar portion 11 is provided with three screw holes 21, and the stator 6 described later is fixed by screwing. The printed circuit board 4 is mounted on the fixed frame 3,
It is fixed by a mounting screw 23 at a bent portion 25 provided at one end of the fixed frame 3.

The stator 6 is fitted on the outer peripheral portion 45 of the cylindrical portion 5. The stator 6 includes a core formed by stacking thin electromagnetic steel plates, and an armature coil in which a required winding is wound around the core. The inner peripheral portion 20 bored in the central portion of the stator 6 is fitted into the outer peripheral portion 45 of the cylindrical portion 5, and is screwed into the screw hole 21 of the collar portion 11 by the mounting screw 17, whereby the stator 6 is fixed. To be done.
Specifically, the stator 6 is fixed to the fixed frame 3 (the flange portion 11 of the cylindrical portion 5) via the coupling member 38 and the printed circuit board 4.

As shown in FIG. 4, the connecting member 38 is made of an insulating resin material. Here, in FIG.
Is a plan view and (b) is a cross-sectional view as seen from XX ′ in (a). As is clear from FIGS. 3 and 4, the coupling member 38 is formed integrally with the annular base portion 42, and the protruding portion 3 is formed.
9 and the engaging piece 40, and all three of them are arranged at equal intervals in the circumferential direction. Similarly, on the inner circumference side of the annular base portion 42, three groove portions 41 are equally arranged in the circumferential direction.

The protrusion 39 formed on the annular base 42 is
It is formed so as to project in one direction of the axis 46 and corresponds to the through hole 18 formed in the stator 6. Further, the engagement piece 40 is formed so as to project outward in the radial direction, and its end portion hangs down (to the other side in the direction of the axis 46) and is provided corresponding to the hole portion 26 of the printed circuit board 4. . The tip of the engaging piece 40 is formed in a substantially tapered shape, and is engaged and fixed in the hole 26 by elastic bending of the engaging piece 40 itself. Further, the groove portion 41 forms an insertion portion of the mounting screw 17 used when fixing the stator 6 to the collar portion 11.

Therefore, the connecting member 38 is interposed between the stator 6 and the printed circuit board 4 and performs the following operation. That is, the stator 6 and the printed circuit board 4 are electrically insulated and positioned in the circumferential direction and the axis 46 direction. The connecting member 38 is used to temporarily hold the stator 6 and the printed circuit board 4 when the brushless motor is assembled. For temporary holding, the stator 6 and the printed circuit board 4 are temporarily assembled in advance. At that time, the projection 39 of the coupling member 38 is inserted into and held in the through hole 18 of the stator 6 and is also engaged. The piece 40 is engaged with and held by the hole 26 of the printed circuit board 4 by elastic bending. Then, in this state, it is fixed to the fixed frame 3 by the mounting screw 17 described above.
By positioning the stator 6 and the printed circuit board 4 in the circumferential direction, the commutation timing of the stator 6 can be accurately performed.

That is, the connecting member 38 is an assembly assisting member used for fixing the stator 6 and the printed circuit board 4 to the fixed frame 3. After these are fixed together, they have a function as an insulating member for maintaining the electrical insulation between the stator 6 and the printed circuit board 4.

A pair of bearings 9 and 10 are mounted on the inner peripheral portion 44 of the cylindrical portion 5. The rotor 2 is rotatably supported via the bearings 9 and 10. The rotor 2 includes a shaft 1, a rotor yoke 7 integrally fixed to the shaft 1, and a rotor magnet 8 provided on an inner peripheral portion of an annular wall 29 of the rotor yoke 7. The shaft 1 is fitted and fixed to a base portion 12 provided on the horizontal portion 30 of the rotor yoke 7, and the base portion 12 and the rotor yoke 7 are fixed by a mounting screw 13.

As shown in FIG. 2, in the rotor magnet 8, magnets 36 made of a ferrite material formed in a segment shape are annularly arranged with a required number of magnetic poles (8 poles in the illustrated example). It is arranged to face the stator 6 in the radial direction. The segment-shaped magnets 36 are arranged at equal intervals in the circumferential direction, and a magnetic resin material is interposed (filled) in each adjacent gap 37.
As the resin material, for example, polyamide resin or the like is used, and a magnetic material such as ferrite is mixed therein. A resin material forming portion 35 made of the same resin material is provided in an annular shape at one end of the rotor magnet 8. These are provided by integrally molding the segment magnet 36 with the above resin.

Therefore, there is no need to attach the segment magnets 36, and there is no need to arrange the magnets in the circumferential direction at equal intervals. Further, since the resin material with which the gap 37 is filled has magnetism, the magnetic flux between the magnetic poles does not diverge, so that the cogging torque with respect to the stator 6 can be reduced. Further, in the resin material forming portion 35, north poles and south poles are alternately magnetized in the circumferential direction, and the axis 4
FG pattern 2 on the printed circuit board facing in 6 directions
Corresponds to 4. Therefore, the rotor 2 formed integrally
In addition, it can be easily magnetized separately from the rotor magnet 8.
There is no need to attach a separate FG-dedicated magnet as in the conventional case.

The bearing 9 is provided with a preload spring 14 in contact with a step portion 32 formed on the inner peripheral portion 44 of the cylindrical portion 5. Further, the bearing 10 includes the retaining ring 15 fitted on the shaft 1 and the step portion 31 of the cylindrical portion 5 so that the preload spring 1
The preload by the action of 4 is added.

Next, FIG. 5 is a sectional view showing another embodiment of the brushless motor of the present invention. The brushless motor shown in FIG. 5 is basically the same as the already described brushless motor, and only the differences will be described. The brushless motor of this embodiment is provided with a reduction gear inside. In FIG. 5, a rotation detector 61 is mounted on the printed circuit board 52 so as to correspond to the axial direction of the rotor magnet 69. Therefore, the rotation detector 61 outputs a detection signal in accordance with the rotation of the rotor magnet 69. The rotor magnet 69 has substantially the same configuration as the configuration shown in FIG. 2 which has already been described.
Is magnetized. That is, this resin material forming portion 99
The N pole or the S pole is magnetized at one location in the circumferential direction, and a predetermined detection signal is output to the rotation detector 61 in response to the rotation of the rotor magnet 69.

The fixed frame 50 includes the rotor magnet 6
A cylindrical portion 73 that rotatably supports the gear 9, peripheral walls 51 and 54 that define a gear accommodating space, and a collar portion 53 that corresponds to the printed circuit board 52 are integrally formed. Bearings 67 and 68 are interposed in the cylindrical portion 73 of the fixed frame 50 to rotatably support the motor shaft 56. A gear portion 70 is formed on the output side of the motor shaft 56. A gear portion 58 of the output shaft 57 is provided in mesh with the gear portion 70. Output shaft 57
Both ends of the bearing are rotatably supported by bearings 59 and 60.

The bearing 60 is the flat portion 7 of the fixed frame 50.
4 is fitted and attached to the receiving portion 62 provided on the No. 4. Since the receiving portion 62 is formed integrally with the fixed frame 50, the number of parts can be reduced, and the assembly error such as the axis deviation can be minimized. Further, the bearing 59 is fitted and mounted on the flange plate 51 that is fixed by being bonded to the fixed frame 50. The retaining ring 64 fitted in the outer ring portion of the bearing 59 prevents the bearing 59 from coming off. In the brushless motor of this embodiment, the outer ring outer peripheral portion 63 itself of the bearing 59, which is a bearing on the output shaft side, is fitted into the device on the other side to be mounted, so-called a spigot. For this reason, it is not necessary to perform special spigot processing on the conventional flange portion, and therefore the labor of processing is saved.

Electronic components (not shown) are mounted on the printed circuit board 52, but the heat radiating action of the fixed frame 50 itself is utilized for the electronic components with particularly high heat generation. That is, the collar portion 5 formed integrally with the fixed frame 50
3, the electronic component 65 is fixed, and its lead wire 66 is connected to the printed circuit board 52. Therefore, since it is not necessary to use a heat dissipation means such as a heat sink on the printed circuit board, the number of parts can be reduced and the motor can be downsized.

Although the embodiment of the brushless motor according to the present invention has been described above in detail, the invention is not limited to this.
Modifications are free within the scope of the present invention. For example, in the present embodiment, the structure of the rotor magnet 8 has been described as a so-called outer rotor motor type in which the rotor 2 is arranged coaxially outside the stator 6 in the radial direction. The rotor is also applied to the motor type. Therefore, the segment magnets can be integrally formed and used with the resin material having magnetism as well. Further, the rotor 2 can be freely designed even if it has a large length in the longitudinal direction, or conversely it has a flat shape. In addition, it goes without saying that the number of magnetic poles and the shape of segment magnets can be freely selected.

[0028]

Since the brushless motor of the present invention has the above-mentioned structure, it has the following effects. That is,
It is possible to obtain a brushless motor that is easy to manufacture and that reduces cogging while using a rotor magnet composed of segment magnets. Further, it is possible to obtain a brushless motor in which another magnet for detecting a rotation or for generating a detection signal such as FG can be easily and accurately provided in the rotor magnet.

[Brief description of drawings]

FIG. 1 is a sectional view showing an entire brushless motor according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a part of the brushless motor appearing in FIG. 1 in a developed manner.

FIG. 3 is a perspective view showing a part of the brushless motor appearing in FIG. 1 in a developed manner.

FIG. 4 shows one of the components used in FIG. 1, (a) is a plan view, and (b) is a sectional view thereof.

FIG. 5 is a sectional view showing an entire brushless motor according to a second embodiment of the present invention.

[Explanation of symbols]

 1 Shaft 2 Rotor 3 Fixed Frame 4 Printed Circuit Board 5 Cylindrical Part 6 Stator 7 Rotor Yoke 8 Rotor Magnet 38 Coupling Member

Claims (2)

[Claims] 1. A brushless motor comprising a stator and a rotor magnet which is rotatably supported coaxially with the stator, wherein the rotor magnet has segment magnets formed in an annular shape with a predetermined gap in the circumferential direction. A brushless motor, wherein the brushless motor is disposed and formed with a magnetic resin material interposed in the gap. 2. The magnetic resin material forming portion is provided at an end portion in the axial direction of the rotor magnet, and the magnetic material forming portion has N poles and S poles alternately in the circumferential direction, or The brushless motor according to claim 1, wherein required magnetic poles are magnetized.