JP3304456B2 - Field magnets for small motors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tape recorder, a CD
The present invention relates to a field magnet that constitutes a small motor used for driving audio equipment and other equipment such as players, and is particularly excellent in general versatility and mass productivity, and has been improved in incorporation into a housing. The present invention relates to a field magnet.

[0002]

2. Description of the Related Art FIG. 3 is a partial sectional side view showing an example of a small motor to which the present invention is applied. In FIG. 3, reference numeral 1 denotes a housing, which is formed of a metal material such as soft iron into a bottomed hollow cylindrical shape, and has, for example, a hollow cylindrical field magnet 2 fixed to the inner peripheral surface. Reference numeral 3 denotes an end plate, which is formed of, for example, a thermoplastic resin material so as to be fitted into the opening of the housing 1. Then 4
Is a rotor, and an armature 5 facing the magnet 2
And a commutator 6, which are rotatably supported by bearings 7, 8 provided on the housing 1 and the end plate 3, respectively.

Reference numeral 9 denotes a brush arm, which is formed of a conductive material in a plate shape, includes a brush 10 which is slidably engaged with the commutator 6, and is provided in the end plate 3. An input terminal 11 electrically connected to the brush arm 9 is provided in the end plate 3. The input terminal 11 is connected to the armature 5 from an external DC power supply via the brush arm 9, the brush 10, and the commutator 6. Power can be supplied.

With the above configuration, when a current is supplied to the armature 5, the armature 5 existing in the magnetic field formed by the magnet 2 fixed to the inner peripheral surface of the housing 1.
, The rotor 4 can be rotated, and various devices connected to the rotor 4 can be driven.

[0005] The field magnet 2 constituting the small motor can be formed by a powder metallurgy molded sintered body such as a ferrite magnet.
There is a means formed by a rubber magnet as described in JP-A-565-565 and the like. That is, as shown in a perspective view in FIG. 4, a rectangular sheet formed of a mixture of ferrite powder and rubber is wound into a hollow cylindrical shape to form a field magnet 2.

[0006]

The conventional magnet 2 has an energy product of a low value of 1.2 to 2.0 MGOe. To improve the driving torque of a small motor, the volume of the magnet 2 must be increased. If it is not possible to cope with it, the size of the small motor will inevitably increase, and various devices using the small motor as a drive source must also be increased in size. However, the space allowed for mounting a small motor in these various devices is limited, and it is impossible to increase the size of the small motor.

On the other hand, in recent years, rare-earth magnets having a large energy product have been frequently used, and are increasingly used as field magnets for small motors. However, since the rare earth magnet has a large price and energy product as compared with the ferrite magnet, the thickness of the magnet 2 in FIG. Below).

Forming such a thin sheet into a hollow cylindrical shape and assembling it into the housing 1 shown in FIG. 3 is extremely complicated, and greatly reduces workability.
Further, since the wall thickness is small, it is difficult to ensure roundness when wound, and when the housing 1 is assembled into the housing 1, the inner surface of the housing 1 and the outer surface of the magnet 2 are in close contact with each other. However, there is a problem that the magnetic resistance is increased and motor characteristics are degraded.

Further, the above-mentioned structure in which the field is formed by the rare-earth magnets has the same output as the case in which the field is formed by the ferrite-based magnets. 4 are different from each other, the components cannot be shared, and the production efficiency is lowered.

In order to solve the above problem, the present applicant has already filed an application for a device having the contents shown in FIG. In the magnet 2 shown in FIG. 5, a predetermined region in the central portion in the magnetization direction indicated by an arrow is formed by a magnet having a high energy product, for example, a rare earth magnet 21, and the other region is a magnet having a low energy product. , For example, formed by a ferrite magnet 22.

With the above configuration, the workability has been improved, the components have been shared, and the motor output has been increased. However, it has been found that there are still the following problems. That is, since the magnets 21 and 22 are made of different materials and the outer shape of the magnet 21 is complicated as shown in FIG. 5, the production of the molding die is not only complicated and expensive, but also the mass productivity is low. There is a point.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems existing in the prior art and to provide a magnet for a field motor of a small motor which can be used in common and has excellent mass productivity.

[0013]

According to a first aspect of the present invention, there is provided a field magnet for a small motor, which is fixed to an inner peripheral surface of a housing of the small motor to form a field. The vicinity of the rotor-side inner peripheral surface of a predetermined region in a cross section of a plane including the motor axis is formed by a magnet having a large energy product, and the other region is formed by a magnet having a small energy product , and
Magnets with large energy products are placed all around the inner peripheral surface.
It formed in a hollow cylindrical shape which, employing the technical means that.

According to a second aspect of the present invention, there is provided a field magnet for a small motor, which is fixed to an inner peripheral surface of a housing of the small motor and forms a field, in a predetermined cross section of a plane including a motor axis. The region near the rotor-side inner peripheral surface is formed by a magnet having a large energy product, and the other region is formed by a resin material.
The technical means that a magnet having a large product was formed in a hollow cylindrical shape arranged on the entire inner peripheral surface was adopted.

[0015] soluble by the above-mentioned invention, a mixture consisting mainly of the bonding material a magnet and a ferromagnetic material powder
It can be formed to have flexibility . In this case, as the ferromagnetic material powder, a magnet having a large energy product is, for example, a rare-earth magnet such as an Sm-Co-based or Nd-Fe-B-based magnet. It is preferable to use ferrites such as Sr ferrite and Ba ferrite.

As the bonding material, rubber and resin materials can be used. In this case, it is necessary to select a material that can mix a relatively large amount of ferromagnetic material powder and can maintain flexibility. As the rubber, natural rubber, neoprene rubber, nitrile rubber, butyl rubber, polyisobutylene, hyvalon, chlorinated polyethylene and the like can be used.

On the other hand, when the resin material is thermoplastic,
Nylon resin, polypropylene, polyethylene, ethyne / vinyl acetate copolymer, modified polyphenylene oxide and the like. In the case of thermosetting, phenol resin, epoxy resin, unsaturated polyester and the like are used. However, it is preferable to use a nylon resin in terms of mechanical strength, magnetic properties, mass productivity, cost, and the like.

As the magnet forming means, injection molding and compression molding can be applied, but it is preferable to use extrusion molding means.

[0019]

According to the above construction, the outer dimensions of the field magnet can be formed substantially in the same manner as a normal magnet, thereby improving workability and using a large amount of expensive rare earth magnet. , And the manufacturing cost can be reduced in combination with the improvement in mass productivity.

[0020]

FIG. 1 is an explanatory view showing an embodiment of the present invention.
(A) is a perspective view, (b) is an exploded perspective view, and the same parts are denoted by the same reference numerals as in FIGS. 3 to 5. In FIG. 1, magnets 21 and 22 are made of Nd—Fe—B-based and Sr ferrite-based magnetic powder and nylon resin, respectively.
For example, it is molded by mixing at a weight ratio of 90:10. In this case, the magnet 22 has, for example, an outer diameter of 22.8.
mm, 20 mm in axial length, 2.0 mm in thickness, formed in a hollow cylindrical shape, and 1.1 mm thick, 12 mm in axial length approximately at the center of the inner peripheral surface
Is formed by burying the magnet 21 integrally. The magnetic energy products of the magnets 21 and 22 are each 6MGOe
And 1.4MGOe.

In order to form the field magnet 2 as described above, the magnets 21 and 22 formed in a sheet shape as shown in FIG. Or formed by so-called two-color molding commonly used in injection molding means. Then, the sheet-shaped molded body may be cut into a predetermined size and wound into a hollow cylindrical shape.

The magnet 2 shown in FIG. 1A is fixed in the housing 1 shown in FIG. 3, and a rotor 4 having an outer diameter of 18 mm and an axial length of 12.5 mm is assembled. When the magnet 2 is magnetized, the amount of magnetic flux is 6.6 × 10
^-5 Wb was obtained. This is because the field magnet 2 is replaced with the conventional S
The amount of magnetic flux when only r ferrite magnet is used
It was confirmed that the increase was about 15% with respect to 5.7 × 10 ⁻⁵ Wb.

FIG. 2 is an end view showing a modification of the magnet 2 shown in FIG. That is, the cross-sectional shape of the magnet 21 indicated by hatching in FIG. 2 can be selected from various geometric shapes, and the shape and dimensions are set in consideration of the characteristics required for a small motor. be able to.

In the present embodiment, an example in which the magnet 21 having a high energy product is held or supported by the magnet 22 having a low energy product has been described. Can be expected. As the resin material in this case, the same material as the bonding material forming the magnets 21 and 22 can be used, and the molding means is also the same.

[0025]

[0026]

Since the present invention has the configuration and operation as described above, the following effects can be obtained. (1) The amount of expensive rare earth magnets used can be reduced to a necessary minimum, and material costs can be reduced. (2) Even a rare-earth magnet having a small thickness can be installed at a predetermined position with high dimensional accuracy and workability can be greatly improved. (3) Since the external dimensions can be formed in the same manner as the field magnet of the normal specification, the components of the small motor can be shared, and the manufacturing cost can be reduced in combination with (1).

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention, wherein (a) is a perspective view and (b) is an exploded perspective view.

FIG. 2 is an end view showing a modification of the magnet 2 shown in FIG.

FIG. 3 is a partial cross-sectional side view showing an example of a small motor to which the present invention is applied.

FIG. 4 is a perspective view showing a magnet 2 in FIG.

FIG. 5 is a perspective view showing a magnet 2 in the improved device.

[Explanation of Signs] 2,21,22 Magnet

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02K 1/17 H02K 23/04 H02K 15/03

Claims (3)

(57) [Claims] 1. A field magnet for a small motor, which is fixed to an inner peripheral surface of a housing of the small motor and forms a magnetic field, wherein a magnet in a predetermined area in a cross section of a plane including a motor axis is disposed on a rotor side. The vicinity of the peripheral surface is formed by a magnet having a large energy product, and the other region is formed by a magnet having a small energy product.
A magnet for a field of a small motor, wherein the magnet is formed in a hollow cylindrical shape arranged on the entire inner peripheral surface . 2. A field magnet for a small motor, which is fixed to an inner peripheral surface of a housing of the small motor and forms a magnetic field, wherein a magnet in a predetermined area in a cross section of a plane including a motor axis is disposed on a rotor side. The surrounding area is formed by a magnet with a large energy product, the other area is formed by a resin material ,
And the magnet with the large energy product is all around the inner peripheral surface.
A magnet for a field of a small motor, wherein the magnet is formed in a hollow cylindrical shape. 3. The magnet for a field of a small motor according to claim 1, wherein the magnet is made of a mixture containing a ferromagnetic material powder and a binder material as main components. .