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Direct-current motor
| Details |
Inventors: Harada, Hiroyuki; Tanaka, Takeshi; Tanino, Toshihiro;
Assignee: Asmo Co., Ltd. (Shizuoka-ken, JP)
Primary Examiner: Nguyen; Tran
Assistant Examiner:
Attorney, Agent or Firm: Crompton, Seager & Tufte, LLC
The armature of a direct-current motor is formed by an armature core and armature coils. The core includes teeth, which are arranged at a pitch of a predetermined angle. The coils are wound about every group of selected teeth of a predetermined number. Two magnets face each other with the armature in between. Each magnet includes main portion, an extended portion, which extends from the main portion, and a first weak flux part. The first weak flux part is located in the vicinity of the border of the extended portion and the main portion. The first weak flux part extends along one pitch of the teeth. The flux of the first weak flux part gradually increases along the rotation direction of the armature. The motor also includes a commutator, which has segments. The segments are connected to each coil. A pair of brushes can contact each segment. The brushes supply current to the coils through the segments. During commutation, each brush establishes a short circuit in an adjacent pair of the segments, thereby changing the direction of current flowing through the coil. When commutation is started, the advancing end of the first tooth in one of the teeth groups, the first tooth being located at the most advanced position in the group in the rotation direction of the armature, is aligned with the first weak flux part of one of the magnets. |
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DETAILED DESCRIPTION Accordingly, it is a first objective of the present invention to provide a direct-current motor that prevents sparks from occurring by locating each brush at an appropriate position relative to the corresponding magnet that has a magnetic flux changer (weak flux part).
A second objective of the present invention is to provide a direct-current motor that reduces cogging torque, thereby operating smoothly with low noise.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a direct-current motor is provided.
The motor includes an armature core, a plurality of armature coils, a plurality of magnets, a commutator, and a pair of brushes.
The core has a plurality of teeth.
The teeth are arranged at a pitch of a first predetermined angle.
Each coil is wound about a different group of teeth having a predetermined number of teeth.
Each tooth is located at the most advancing position in the rotation direction in one of the teeth groups.
The armature core and the armature coils form an armature.
The magnets face one another with the armature in between.
Each magnet includes a main portion, an extended portion, a first weak flux part.
The extended portion extends from the main portion.
The first weak flux part is located in the vicinity of the border of the extended portion and the main portion.
The first weak flux part extends along one pitch of the teeth, and the flux of the first weak flux part gradually increases along the rotation direction of the armature.
The commutator has a plurality of segments.
The segments are connected to each coil.
The brushes can contact each segment.
The brushes supply current to the coils through the segments.
During commutation, each brush establishes a short circuit in an adjacent pair of the commutator segments, thereby changing the direction of current flowing through the coil.
When commutation is started for a group of teeth, the advancing end of the first tooth in that teeth group, the first tooth being located at the most advanced position in the group in the rotation direction of the armature, is aligned with the first weak flux part of one of the magnets
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Generators or Motors 
