Electric motor having brushes and commutator of armature

Details Electric motor having brushes and commutator of armature Electric motor having brushes and commutator of armature

2000-03-30

2001-11-20

Nguyen, Tran (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S234000, C310S235000

Reexamination Certificate

active

06320293

ABSTRACT:

CROSS REFERENCE TO RELATED APPLICATION
This application relates to and incorporates herein by reference Japanese Patent Application No. 11-283078 filed on Oct. 4, 1999.
BACKGROUND OF THE INVENTION
The present invention relates an electric motor having power supply brushes and a commutator of an armature.
In conventional direct current motors having power supply brushes, multiple (for instance, four) brushes are used to reduce load current for each brush when high output is required. It is most desired that two same-polarity brushes contact two segments of a commutator at the same time.
It is however difficult in practice to cause the two same-polarity brushes to contact the corresponding segments at the same time. As a result, the timings of contact of the brushes differ. The timing of power supply to the armature is imbalanced when current flows in one of armature windings. This imbalance will cause fluctuation in the motor rotation, vibration, unusual noise and the like.
These fluctuation in the motor rotation, vibration and unusual noise arising secondarily will lessen response characteristics in operation, cause discomfort and the like in the case that the motor is applied, for instance, to home appliances and automotive devices such as an electric power steering device.
In the conventional motor, therefore, the windings are shorted by shorting wires between the same-phase segments to provide strapping connection. This connection reduces the fluctuation in the motor rotation, vibration and unusual noise.
The conventional strapping connection requires a separate special winding process. The winding work increases, because each shorting wire is wound around a slotted core of an armature. The armature and hence the electric motor thus result in high cost. Further, the shorting wire would cause undesirable influence to the armature in respect of inductance and the like, because it is wound a rather long distance.
Further, in the armature with the strapping connection, the conventional brushes which contact the segments of the armature has a narrow segment-contacting surface. The brush has only a width sufficient to bridge at most two segments at the same time. As a result, the brushes of the same polarity cannot contact the same-phase segments at the same time, when the interval between the same-polarity brushes varies. This results in variations in the contact timing.
That is, when one brush contacting a segment leaves from one segment and contacts the next segment, it may happen that the other brush cannot contact another segment which follows a segment which is in the same phase as the one segment contacted by the one brush. In this instance, when the one segment leaves the one segment and contacts the next segment, the voltage applied to from the brush to the next segment cannot be absorbed causing sparks and noises. This is an impediment to prolong the life of the electric motor and to reduce noises.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an electric motor and a commutator of an armature which is capable of reducing motor rotation fluctuation, vibrations and noises as well as prolonging its product life.
According to the present invention, each of same-phase segments of a commutator is shorted by a shorting member, and each power supply brush normally contacts at least two segments. The shorting member may be a conductive plate or wire. As a result, even when one power supply brush of a plurality of power supply brushes of the same polarity respectively contacting the same-phase segments dislocates or jumps not to contact one of the segments, the other power supply brush of the same polarity contacts the other same-phase segment without fail. Thus, current flows to the one same-phase segment through the shorting member.


REFERENCES:
patent: 5760517 (1998-06-01), Stolpmann
patent: 5929579 (1999-07-01), Hsu
patent: 6127759 (2000-10-01), Tanaka et al.
patent: 61-112556 (1986-05-01), None
patent: 7-44810 (1995-05-01), None

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