JPH11136883A - Dc motor with brush - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC motor with a brush which can attain high motor efficiency, long life of the brush and a commutator, and high cooling performance. SOLUTION: A DC motor with a brush is provided with a stator yoke 3 consisting of a plurality of yoke parts 3a constituted by layering steel plates so as to form a magnetic path, and a yoke jointing part 3b where a neutral band part is positioned with the yoke parts 3a joined thinly at its inside respectively, a permanent magnet 4 fitted at respective recessed parts 3c between the yoke parts 3a, and an armature 10 facing the inner periphery surface of the stator yoke 3 through an air-gap. The DC motor is constituted so that the yoke jointing part 3b may be formed beside the permanent magnet 4 and separated from the outer periphery surface of the armature 10, a groove part 16 may be formed at a part between the yoke jointing part 3b of the stator yoke 3 and the armature outer periphery surface, and a non-magnetic heat transfer material 17 may be fitted at the groove part 16. It is thus possible to prevent generation of braking torque even in a small type DC motor, thereby improving motor efficiency and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless DC motor having a stator yoke comprising a plurality of yoke portions formed by stacking steel plates and a yoke connecting portion connecting the yoke portions. It is about.

[0002]

2. Description of the Related Art A conventional brushed DC motor is shown in FIG.
And it is comprised as shown in FIG. In the figure,
1 is a DC motor, 2 is a stator, and comprises a stator yoke 3 and a permanent magnet 4 such as an alnico magnet or a ferrite magnet. The stator yoke 3 includes a plurality of yoke portions 3a that form a magnetic path formed by laminating steel plates, and a yoke connecting portion 3b in which the yoke portions 3a are thinly connected on the inner side and a neutral band portion is located. It is composed of 3c is a concave portion formed between the yoke portions 3a. The permanent magnet 4 is provided in the recess 3
c. Reference numeral 5 denotes a load-side bracket, and reference numeral 6 denotes a non-load-side bracket, which are mounted on the axial end surface of the stator yoke 3, respectively, and rotatably rotate the rotating shaft 9 via a load-side bearing 7 and a non-load-side bracket bearing 8. It is supported. An armature 10 includes an armature core 11 and an armature core coil 12 wound around the armature core 11. The armature 10 is mounted on the rotating shaft 9 so as to face the inner peripheral surface of the stator yoke 3 via a gap. A brush holding device 13 is attached to the non-load side bracket 5 and has a brush 14 slidably mounted therein. 1
A commutator 5 is attached to the rotating shaft 9 and is in contact with the brush 14. As described above, in the conventional DC motor, the stator yoke 3 has a structure in which, for example, four yoke portions 3a are connected by the yoke connection portion 3b formed as long as possible so that the magnetic flux does not easily pass, Yoke 3a
The permanent magnet 4 is inserted into the concave portion 3 formed therebetween, and the permanent magnet 4 is sandwiched between the yoke portions 3a to ensure dimensional accuracy, reduce the number of parts, and improve productivity. ing.

[0003]

However, such a conventional brushed DC motor has the following problems. (1) Since the cross-sectional shape of the stator yoke 3 on the armature side is circular and the gap with the stator yoke 3 is uniform, the magnetic flux distribution is
As shown in FIG. 5, the neutral band A is much narrower than the rectifying band B. In particular, in the case of a motor having a structure in which brushes, armatures and the like have no dimensional margin, such as a small DC motor, the neutral band A Does not end the rectification, a portion C that becomes an ineffective magnetic flux is generated, and an induced voltage is generated in the rectification coil. This causes a braking torque by short-circuiting between the brushes, thereby increasing the no-load loss torque and reducing the efficiency of the motor. (2) Since a part of the field magnetic flux which should be converted to the output torque becomes the braking torque, the permanent magnet is not sufficiently utilized, and the rectification is performed in a state where the induced voltage is generated. And shorten the life of the commutator. (3) Due to the laminated steel plate structure, heat flow in the longitudinal direction is hindered by the effect of the insulating layer on the surface of the steel plate, resulting in poor cooling performance. Therefore, an object of the present invention is to provide a brushed DC motor having good motor efficiency, long life of brushes and commutators, and good cooling performance.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to a plurality of yoke portions forming a magnetic path formed by stacking steel plates, and each of the yoke portions is thinly connected inside. A stator yoke comprising a yoke connecting portion in which a sex belt portion is located; a permanent magnet attached to each recess between the yoke portions; and an electric machine opposed to an inner peripheral surface of the stator yoke via a gap. In the brushed DC motor having the armature, the yoke connecting portion is formed near the permanent magnet away from the armature outer circumferential surface, and the yoke connecting portion of the stator yoke and the armature outer circumferential surface. A groove is formed in a portion between the grooves, and a non-magnetic heat transfer material is attached to the groove. By the above-mentioned means, even in a small DC motor, no braking torque is generated, and the motor efficiency is improved. In addition, since all the magnetic flux can be used to generate output torque, there is no waste in the use of permanent magnets, and since rectification ends in the neutral band,
Extends brush and commutator life. In addition, since a non-magnetic and highly heat-conductive material is inserted into the groove of the stator yoke, heat radiation from the armature, particularly in the longitudinal direction, is improved, and the cooling performance of the DC motor is improved.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a front sectional view of a DC motor showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a magnetic flux distribution of the DC motor of the present invention. The same reference numerals as those in FIGS. 3 to 5 denote the same or corresponding members, and a description thereof will be omitted. As shown in FIG. 1, the brushed DC motor 1 of the present invention separates the yoke connecting portion 4 where the neutral band portion is located from the outer peripheral surface of the armature core 12 and is located near the permanent magnet 6. A groove 16 is formed in a portion between the yoke connecting portion 4 of the stator yoke 2 and the outer peripheral surface of the armature core 12.
Is formed, and a heat transfer material 17 such as a non-magnetic aluminum material having high heat conductivity is attached to the groove portion 16. The heat transfer material 17 is placed as close as possible to the armature 10, which is a heat source, and is mounted over the entire area in the axial direction. The cross-sectional shape is formed in a trapezoidal shape in consideration of easy installation.
Further, by bringing the load-side axial end face into close contact with the load-side bracket 5, heat from the armature 10 is transmitted to the load-side bracket 5 well. Further, the width of the yoke 3a is set to such an extent that the magnetic flux is not saturated,
The yoke connecting portion 3b is formed as thin as possible as long as mechanical strength and dimensional accuracy can be ensured. In such a configuration, since the yoke connecting portion 3b where the neutral band portion is located secures a sufficient magnetic air gap with respect to the armature 10, as shown in FIG. The magnetic flux distribution is wider than the rectification band B, and no induced voltage is generated in the rectification coil. Therefore, no braking torque is generated, and the efficiency of the electric motor is improved. Moreover, since all the magnetic flux can be used for generating the output torque, there is no waste in using the permanent magnet. In addition, since rectification ends in the neutral band A,
No induced voltage is generated in the rectifying coil, and the life of the brush 14 and the commutator 15 is extended. Further, the armature 10
A non-magnetic, highly heat-conductive heat transfer material 17 is inserted in the entire axial direction of the groove 16 facing the outer peripheral surface of the armature with a gap therebetween, so that the heat generated by the armature 10 is Not only the portion 3a but also the heat transfer material 17 from the entire axial direction,
As a result, the amount of heat radiation from the armature 10, which is a heat source, increases, and the DC motor is cooled well. In addition,
Since the load-side axial end face is in close contact with the load-side bracket 5, heat from the armature 10 is transmitted well to the load-side bracket 5, and cooling is further performed well. The heat transfer material 17 may be integrated with the load-side bracket 5, and in this case, there is an effect that the dimensional accuracy, the number of parts is reduced, and the productivity is improved.

[0006]

As described above, according to the present invention, the following effects can be obtained. (1) No braking torque is generated by circulating current, motor efficiency is improved, and all magnetic flux can be used for output torque generation, so there is no waste in using permanent magnets. (2) Since the commutation is completed in the neutral band, the life of the brush and the commutator is extended. (3) Since a non-magnetic heat conductive material having high thermal conductivity is inserted into the groove of the stator yoke, heat radiation from the armature, particularly in the longitudinal direction, is improved, and the cooling performance of the DC motor is improved. I do.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a DC motor showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a magnetic flux distribution of the DC motor of the present invention.

FIG. 3 is a front sectional view of a DC motor showing a conventional technique.

FIG. 4 is a side sectional view of a DC motor showing a conventional technique.

FIG. 5 is an explanatory diagram showing a magnetic flux distribution of a conventional DC motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC motor, 2 stator, 3 stator yoke, 3a yoke part, 3b yoke connection part, 3c recess, 4 permanent magnet, 5 load side bracket, 6 non-load side bracket, 7 load side bearing, 8 anti-load Side bearing, 9 rotating shaft, 10 armature, 11 armature core, 12 armature coil, 13 brush holding device, 14 brush, 15 commutator, 16 groove, 17 heat transfer material

Claims (1)

[Claims] 1. A stator comprising: a plurality of yoke portions each serving as a magnetic path formed by laminating steel plates; and a yoke connection portion where each of the yoke portions is thinly connected inside and a neutral band portion is located. A yoke, a permanent magnet attached to each recess between the yoke portions, and an armature facing the inner peripheral surface of the stator yoke via a gap, wherein the yoke connection portion Is formed near the permanent magnet away from the armature outer peripheral surface, and a groove is formed in a portion between the yoke connecting portion of the stator yoke and the armature outer peripheral surface,
A brushless DC motor, wherein a nonmagnetic heat transfer material is attached to the groove.