JPS6142504B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC motor, and more particularly to a DC motor having a field formed of ferrite permanent magnets.

Generally, a DC motor having a field formed of ferrite permanent magnets has ferrite permanent magnets 21, 22, 23, and 2 on the inner surface of a cylindrical stator yoke 1, as shown in the cross section of FIG. 1, for example.
4 is fixed as a field, and the inside of the field is connected to the armature 4.
is configured to rotate.

In the structure shown in FIG. 1, the armature current 5 flowing through the windings of the armature 4 causes the magnetic circuit 6 to
Magnetic flux Φ ₁ Φ ₂ is generated in a and 6b, but when the current increases to a certain degree or more, the magnetic flux Φ generated by the armature current 5 becomes excessive, and even if the armature current 5 disappears, the ferrite There is a problem in that a so-called demagnetization effect occurs in which the magnetic flux of the permanent magnet 21 decreases from the previous state, which has an adverse effect. In order to solve this problem, it is conceivable to increase the thickness of the ferrite permanent magnet 21, but this is unfavorable in terms of field dimension design and increases cost. Due to the poor machinability of the ferrite permanent magnet, it is difficult to make the gap precision uniform between the inner peripheral surface of the field pole and the outer peripheral surface of the armature, resulting in uneven magnetic flux distribution in the air gap. If the magnetic flux is locally demagnetized by the reaction magnetic flux, the magnetic flux distribution in the air gap becomes non-uniform, resulting in a problem that rotational ripples of the armature occur.

Therefore, a structure as shown in FIG. 2 has been proposed in order to reduce the demagnetization effect of the field permanent magnet due to the armature current without increasing the thickness of the ferrite permanent magnet. That is, in FIG. 2, relatively thick pole shoes 31, 32, 33 made of a ferromagnetic material are attached to the inner peripheral surfaces of ferrite permanent magnets 21, 22, 23, 24 attached to the inner peripheral surface of the cylindrical yoke 1. , 34 are fixed to form a field structure. This pole show 31,3
By providing 2, 33, and 34, a large portion of the armature reaction magnetic flux Φ ₃ becomes the pole shoe 3.
1, the armature reaction magnetic flux Φ passes through the magnetic path 6c containing the ferrite permanent magnet 21.
The magnetic flux passing through the ferrite permanent magnet 21 will therefore be reduced and the demagnetizing effect on the ferrite permanent magnet 21 will be reduced. However, since this conventional pole shoe is usually made of soft iron material and has a relatively large thickness in the radial direction, it is effective as a measure to reduce the above-mentioned demagnetization effect _. A portion of the armature winding rectifying regions 71 and 72 of the armature 4 has defects that deteriorate the commutating characteristics of the armature, such as generation of strong rectifying sparks, and furthermore, extrusion molding and cutting Another problem is that the manufacturing cost is high.

Therefore, as shown in FIG. 3, a DC motor having a field structure aimed at reducing both the aforementioned demagnetization effect and the armature reaction magnetic flux passing through the commutating region has already been proposed. There is. That is, in FIG. 3, ferrite permanent magnets 4 are fixedly arranged in equal parts on the inner peripheral surface of the cylindrical stator yoke 1.
1, 42, 43, and 44 are provided with a pair of notched shoulders 49 for reducing the width in the circumferential direction of the inner circumferential surface on the side facing the armature 4, and the inner circumferential surface thereof has a thickness of 1 mm.
Thin iron plate 45, 4 made of soft iron with a thickness of about 2 mm
6, 47, and 48 are bonded to each other so as to cover the entire inner peripheral surface. By forming the armature in this way, _the magnetic flux Φ 4 of the armature reaction magnetic flux Φ of the armature 4 passes through the thin iron plate 41, that is, the magnetic circuit 6d.
is reduced from the magnetic flux Φ ₃ passing through the thick iron plate 31 shown in FIG. 2, and the magnetic flux passing through the rectifying regions 71 and 72 is reduced. Further, the width of the iron plate 45 in the circumferential direction is narrower at the shoulder portion 49 than the width of the permanent magnet 41, so that both ends of the iron plate 45 in the circumferential direction are separated from the rectifying regions 71 and 72 by that amount. Therefore, the armature reaction magnetic flux passing through the rectifying regions 71 and 72 is formed so as to be further reduced. By forming the field in this way,
The conventional DC motor shown in Figure 3 is designed to reduce damage caused by armature reaction magnetic flux, which deteriorates the rectification characteristics of the armature winding, and also to reduce the demagnetizing effect of the ferrite permanent magnets. be. Further, the thin iron plates 45, 46, 47, and 48 have the advantage that they can be manufactured at low cost by press molding.
The present invention provides rectifying regions 71, 7 in this field structure.
This is intended to further reduce the armature reaction magnetic flux passing through 2 and improve the rectification characteristics.

In other words, in a DC motor with a field formed using ferrite permanent magnets, by devising and improving the field structure, the demagnetizing effect of the ferrite permanent magnets can be reduced, and the commutating characteristics of the armature can be greatly improved. The object of the present invention is to provide a DC motor that can be manufactured at low cost.

According to the present invention, in a DC motor that uses ferrite permanent magnets as field magnetic poles and has a thin iron plate adhesively fixed to the inner peripheral surface of the ferrite permanent magnet facing the outer peripheral surface of the armature, the thin iron plate is fixed in the axial direction. A DC motor is provided, which is characterized by having a long hole.

Embodiments of the present invention will be described in detail below with reference to FIGS. 4 to 8 of the accompanying drawings.

FIG. 4 is a longitudinal cross-sectional view of a DC motor according to the present invention;
5 is a cross-sectional view taken along the line A-A in FIG. 4, FIG. 6 is a perspective view of the ferrite permanent magnet 41 and iron plate 51 shown in FIG. 4, and FIG. Perspective view of the state in which the iron plates 51 are combined, No. 8
The figure shows an iron plate 70 in another embodiment according to the present invention.

In FIG. 4, a stator yoke 1 is sandwiched between cover plates 63 and 64, and ferrite permanent magnets 41 to 44 are fixed to the inside of the stator yoke 1. The inside of the ferrite permanent magnets 41 to 43, that is, the inner circumferential surface facing the armature 4, has a plurality of through holes made of soft iron with a thickness of about 1 mm to 2 mm and extending in the axial direction according to the present invention. Iron plates 51 to 54 are adhesively fixed to the inner peripheral surface so as to cover the entire surface. The armature 4 is fixed to the rotor shaft 60 inside the iron plates 51 to 54 through the inner peripheral surface of the iron plate and a constant gap, and the armature 4 and the bearings 61 are disposed on the cover plates 63 and 64. 62 so as to be rotatable in forward and reverse directions. Furthermore, in order to supply current to the armature 4, a commutator 69 is provided at the rear end of the armature 4, and brushes 67 and 68 are brought into contact with the commutator 69 and moved to the brush holder 6.
It is supported by the cover plate 64 via 5 and 66.

As shown in FIG. 5, a ferrite permanent magnet 41
44 have a width in the circumferential direction slightly smaller than 90 degrees, and are arranged equally along the inner circumferential surface of the stator yoke 1. Also, these ferrite permanent magnets 41 to 44
In order to reduce the width in the circumferential direction of the inner circumferential surface on the side opposite to the outer circumferential surface of the armature 4, cutout shoulders 47 are provided at both ends of the inner circumferential surface. Iron plates 51 to 54 according to the present invention are adhesively fixed so as to cover the entire surface thereof. As described above, these iron plates 51 to 54 are formed by pressing soft iron with a thickness of about 1 mm to 2 mm, and are provided with a plurality of elongated holes 51a extending in the axial direction as shown in FIG. 6A. be. Therefore, as shown in FIG.
The circumferential cross sections of Nos. 1 to 54 are discontinuous through the elongated holes 51a, and since the elongated holes 51a are spaces, air, which is a paramagnetic material, exists. Therefore, the magnetic circuit 6e of the iron plate 51
The branched magnetic flux _Φ5 of the armature reaction magnetic flux Φ passing through is weakened by the air present in this elongated hole 51a. As a result, this shunt magnetic flux Φ ₅ is transferred to the rectifying region 71,
The magnetic flux passing through 72 is also reduced, and damage that adversely affects the rectification characteristics of the armature winding is greatly reduced.

Figure 6 shows ferrite permanent magnet 41 (Figure 6 A)
FIG. 6 is an exploded perspective view of the steel plate 51 and the iron plate 51 (FIG. 6b), respectively. As shown in the figure, the iron plate 51 has a plurality of elongated through holes 5a parallel to the longitudinal direction (axial direction), and is pressed so that the curvature of its outer circumferential surface matches the curvature of the inner circumferential surface of the ferrite permanent magnet 41. It is simply punched and curved. Therefore, the ferrite permanent magnet 41 and the iron plate 51 can be easily assembled together and fixed by adhesive, as shown in FIG. The other field magnetic poles were manufactured using exactly the same process, and these field magnetic poles were equally distributed in the circumferential direction on the inner circumferential surface of the cylindrical stator yoke 1, as shown in FIGS. 4 and 5. By arranging and fixing with adhesive, the field magnetic pole of the DC motor according to the present invention can be easily formed.

FIG. 8 shows another embodiment of the present invention, in which a long hole 70a provided in an iron plate 70 is formed in a direction oblique to the longitudinal end of the iron plate 70. When a field magnetic pole is formed,
Furthermore, consideration has been given to bringing about a skew effect. The overall shape, material, thickness, etc. of this iron plate 70 are the same as the iron plate 51 of the embodiment shown in FIGS. can do.

According to the DC motor constructed as described above according to the present invention, even if the long holes are provided in a thin iron plate, the thin iron plate can be easily punched and curved by press working etc., so the manufacturing cost can be reduced, and the ferrite It is easy to ensure the accuracy of the air gap between the inner circumferential surface of the permanent magnet and the outer circumferential surface of the armature, and the magnetic flux distribution on the inner circumferential surface of the field magnetic pole becomes uniform.
Therefore, it is possible to reduce the rotational ripple of the armature.

In addition, even if an abnormally large current flows through the armature winding, the magnetic flux due to the armature reaction is shunted through the iron plate, which has the effect of reducing demagnetization of the ferrite permanent magnet. Even if the ferrite permanent magnet is partially demagnetized by the current, the magnetic flux distribution on the inner circumferential surface of the field magnetic pole is made uniform by the action of the iron plate, so it is possible to reduce the rotational ripple caused by the above-mentioned polar demagnetization. can. Although the thin iron plate of the present invention is provided with an elongated hole in the axial direction, the effect of making the magnetic flux distribution uniform on the inner circumferential surface of the field magnetic pole is not as good as that of the conventional one shown in Fig. 3. There is virtually no problem compared to continuous thin iron plates.

Furthermore, since the iron plate of the present invention is thin and has elongated holes, the magnetic flux due to armature reaction is shunted, and the amount of magnetic flux passing through the iron plate is smaller than in the case of the conventional thin iron plate described above. Therefore, it is possible to greatly reduce the damage that deteriorates the rectifying characteristics of the armature winding due to the influence of magnetic flux due to armature reaction, and contributes greatly to improving the rectifying characteristics.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views of conventional DC motors, FIG. 4 is a vertical cross-sectional view of a DC motor according to an embodiment of the present invention, and FIG. 5 is a cross-sectional view taken along line A-A in FIG. 4. Figure 6 is a perspective view of the ferrite permanent magnet (Figure 6 A) and iron plate (Figure 6 B) in Figure 1, and Figure 7 is a perspective view showing the assembled state of the ferrite permanent magnet and iron plate in Figure 1. 8 are diagrams showing an iron plate in another embodiment of the present invention. 1... Stator yoke, 4... Armature, 41,
42, 43, 44... Ferrite permanent magnet, 49
...Notch shoulder, 51, 52, 53, 54, 71
...Soft iron plate (pole shoe), 51a, 71a...
...Elongated hole, 60... Rotor shaft, 61, 62... Bearing, 63, 64... Cover plate, 65, 66... Brush holder, 67, 69... Brush, 69... Commutator.

Claims (1)

[Scope of Claims] 1. In a DC motor in which a ferrite permanent magnet is used as a field magnetic pole and a thin iron plate is adhesively fixed to the inner circumferential surface of the ferrite permanent magnet facing the outer circumferential surface of the armature, the thin iron plate is attached in an axial direction. A DC motor characterized by having a long hole. 2. The DC motor according to claim 1, wherein a plurality of the elongated holes are provided in parallel with the axis. 3. The DC motor according to claim 1, wherein a plurality of the elongated holes are provided obliquely to the axis.