JP2002101620A - Dc motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC motor which reduces vibration and noise caused by shrinkage of magnets which are injection-molded when the DC. SOLUTION: A rotor 30 has an inserted material 31 which has a rotor shaft 33 and plastic ferrite magnets 35 which are pushed in and molded on the exterior of the insert material 31 and respectively face the stator 40. A plurality of rectangular wave notches 35a are formed to suppress shrinkage after injection on the outer periphery of the plastic ferrite magnets 35 which respectively face the stator 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC motor, and more particularly, to a DC motor improved to reduce vibration and noise generated when the DC motor is driven due to contraction of an injection-molded magnet.

[0002]

2. Description of the Related Art As shown in FIG. 6, a conventional DC motor includes a rotor 10 and a stator 20 provided outside the rotor 10. The rotor 10 includes an insert 11, a rotor shaft 13 provided on the insert 11, and a plastic ferrite magnet 15.

[0003] Among the manufacturing methods of the rotor 10, there is a method by injection molding. The rotor 10 has an insert 11 in a mold.
Is fixed, and the material of the plastic ferrite magnet 15, that is, the material obtained by mixing the plastic resin and the ferrite powder is inserted into the mold.

An injection molded plastic ferrite magnet 15 does not have magnetism at first, but only takes N and S pole magnetism after following a magnetizing process.

The rotor 10 is provided at a predetermined distance from a stator 20 on which an armature coil (not shown) for generating torque by interacting with a magnetic field generated by a plastic ferrite magnet 15 is wound.

When a voltage is applied to the rotor 10 provided as described above, the N and S poles of the plastic ferrite magnet 15 magnetized by a Hall sensor (not shown) attached to a PCB (not shown). When a voltage is input to the driver output terminal by the internal logic (LOGIC) of the drive IC, a suction and repulsion force acts to rotate the rotor 10 and drive the DC motor. .

[0007] The DC motor as described above has the following problems. That is, the plastic ferrite magnet 15 molded by the insert injection method as described above contracts in a concave shape after injection, as shown by a virtual line in FIG.

If the outside of the plastic ferrite magnet 15 shrinks, it becomes impossible to maintain the gap design specifications between the rotor 10 and the stator 20. Therefore, there is a problem that the surface magnetic flux density of the plastic ferrite magnet 15 is not constant and the overall electric characteristics of the motor become non-uniform.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to reduce the vibration and noise generated when a DC motor is driven due to the contraction of an injection-molded magnet. An object of the present invention is to provide a DC motor capable of reducing sound.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides an insert having a stator, a rotor provided inside the stator, a rotor shaft provided, and an insert. A DC motor characterized by including a plastic ferrite magnet formed outside and having a notch formed on an outer peripheral surface facing the stator.

Here, it is desirable that a plurality of notches are formed in a rectangular wave shape, and that the notches are formed to have a square shape over the upper and lower surfaces of the plastic ferrite magnet.

The notch preferably includes a first notch formed so as to correspond to the magnetic pole boundary between the N pole magnet and the S pole magnet of the plastic ferrite magnet.
In addition, a second notch formed on the N-pole magnet and / or the S-pole magnet of the plastic ferrite magnet may be further included.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. Referring to FIG. 1, a DC motor according to an embodiment of the present invention includes a stator 40 and a rotor 30. The rotor 30 includes an insert 31 on which a rotor shaft 33 is provided, and a plastic ferrite magnet 35 which is pressed and formed on the outside of the insert 31 and faces the stator 40.

The plastic ferrite magnet 35 is formed by an insert injection method in which the insert 31 is stabilized in a mold and the material of the plastic ferrite magnet 35, that is, a material in which a plastic resin and ferrite powder are mixed is pushed into the mold.

The injection-molded plastic ferrite magnet 35 has no magnetism at first, and becomes magnetized with N and S poles only after following the magnetizing process.
Therefore, the plastic ferrite magnet 35 having magnetism is formed by the N-pole magnet 36 and the S-pole magnet 37 which are alternately connected so as to have a substantially donut shape.

Notches 35a are formed on the outer peripheral surface of the plastic ferrite magnet 35 facing the stator 40 to suppress shrinkage after injection. A plurality of notches 35a are formed in a rectangular wave shape. In addition, each notch 35
It is desirable that a be formed to have a square shape over the upper and lower surfaces of the plastic ferrite magnet 35.

Also, as shown in FIG.
Represents a first notch N1 formed to correspond to the magnetic pole boundary line B between the N-pole magnet 36 and the S-pole magnet 37;
An N-pole magnet 36 and a second notch N2 formed on the S-pole magnet 37 are included. Here, the second notch N2 is N
It may be formed only on the pole magnet 36 or the S pole magnet 37.

By forming the notch 35a in this way, the plastic ferrite magnet 35 can be placed in the mold during injection molding.
The flow of the mixture of the plastic resin and the ferrite powder, which is the material of No. 5, becomes smooth, and the shrinkage generated after the injection can be suppressed.

Therefore, the notch 35a formed in the plastic ferrite magnet 35 suppresses the contraction that occurs after the injection, and at the same time, the plastic ferrite magnet 3
5, that is, the gap between the rotor and the stator can be kept constant, and the surface magnetic flux density of the plastic ferrite magnet 35 can be kept uniform.

FIG. 3 shows a main part of a DC motor according to another embodiment of the present invention. The characteristics of the DC motor shown are the N-pole magnet 56 and the S-pole magnet 57.
Notch 5 formed to correspond to magnetic pole boundary line B
5a. That is, in the present embodiment, the plastic ferrite magnet 55 is formed with only the first notch N1 in the above-described embodiment, thereby suppressing the shrinkage of the plastic ferrite magnet 55 after injection.

Hereinafter, as shown in FIG. 1, the operation and effect of the example in which the stator 40 having the slot 41 and the rotor 30 according to an embodiment of the present invention are coupled will be described with reference to FIGS. A description will be given in comparison with the conventional technology with reference to Table 1 below.

FIG. 4 is a graph showing a comparison between the conventional DC motor and the coking torque generated when the DC motor according to the present invention is driven. FIG. 5 is a graph showing frequency conversion of the data shown in the graph of FIG. FIG.

In FIGS. 4 and 5, the conventional example shown by a thick line is an experiment of a conventional DC motor, and the thin line example 1 is an experimental result of a DC motor according to an embodiment of the present invention. Example 2 indicated by a two-dot chain line is a result of an experiment on a DC motor according to another example of the present invention. Also,
Table 1 below summarizes the experimental results of FIGS.

[0024]

[Table 1]

As can be seen from Table 1 and FIGS. 4 and 5,
For comparative example, Kokintoruku about 3.4 * 10 ^- 3 N
・ M and the frequency-converted Cokin torque is about 1.5
* 10 ^- a 3 N · m.

On the other hand, in Experimental Example 1 in which the DC motor according to the embodiment of the present invention was tested, the Cokin torque value was about 1.0.
6 * 10 ^- a 3 N · m, the value of Kokintoruku obtained by frequency conversion of about 0.3 * 10 ^- a 3 N · m. As can be seen, in the experimental example 1, the value of the cokin torque was 53%, and the value of the frequency-converted cokin torque was 80%, as compared with the comparative example.

Further, in Experimental Example 2 were studied DC motor of another embodiment according to the present invention, Kokintoruku value of about 2.2 * 10 - a ^{3 N} · m, the frequency converted Kokintoruku value is about 1.5 * 10 ^- a 3 N · m. Therefore,
Experimental example 2 has a cokin torque value of 35% compared to the comparative example.
It can be seen that similar values were obtained for the frequency-converted Cokin torque values.

The preferred embodiment of the DC motor according to the present invention has been described with reference to the accompanying drawings.
The present invention is not limited to such an example. It is obvious that those skilled in the art can conceive various changes or modifications within the scope of the technical idea described in the claims, and these naturally belong to the technical scope of the present invention. It is understood.

[0029]

As described above in detail, according to the present invention, it is possible to provide a DC motor capable of reducing vibration and noise when the DC motor is driven due to contraction of the injection molded magnet.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing a DC motor according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a portion A of FIG.

FIG. 3 is a plan view schematically showing a main part of a DC motor according to another embodiment of the present invention.

FIG. 4 is a graph showing a comparison between the DC motor shown in FIG. 1 and FIG.

FIG. 5 is a graph showing a frequency conversion of data appearing in the graph shown in FIG. 4 and comparing the data;

FIG. 6 is a plan view schematically showing a conventional DC motor.

FIG. 7 is a side view showing the rotor of FIG. 6;

[Explanation of symbols]

 Reference Signs List 30 Rotor 33 Rotor shaft 35 Plastic ferrite magnet 36, 56 N pole magnet 37, 57 S pole magnet 35a, 55a Notch 40 Stator

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) B29K 103: 06 B29K 103: 06 B29L 31:08 B29L 31:08

Claims (5)

[Claims] 1. An insert having a stator, a rotor provided inside the stator, and having a rotor shaft provided thereon, and a notch formed on an outer peripheral surface of the insert facing the stator. A direct current motor comprising a plastic ferrite magnet formed with a magnet. 2. The DC motor according to claim 1, wherein a plurality of the notches are formed in a rectangular wave shape. 3. The DC motor according to claim 1, wherein the notch is formed to have a square shape over upper and lower surfaces of the plastic ferrite magnet. 4. The method according to claim 1, wherein the notch includes a first notch formed to correspond to a magnetic pole boundary between an N-pole magnet and an S-pole magnet of the plastic ferrite magnet. DC motor as described. 5. The DC motor according to claim 4, wherein the notch includes a second notch formed on an N-pole magnet and / or an S-pole magnet of the plastic ferrite magnet.