Commutator motor

Details Commutator motor Commutator motor

1999-08-06

2001-05-22

Ramirez, Nestor (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S234000, C310S204000, C310S206000

Reexamination Certificate

active

06236137

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a commutator motor comprising a commutator having a hollow cylindrical insulating resin portion and a plurality of segments on an outer circumferential portion of the insulating resin portion with the spaces between each being held by the insulating resin portion.
2. Description of the Related Art
FIG. 16
is a cross-section of a conventional commutator motor
100
. The commutator motor
100
comprises: a cylindrical yoke
101
; permanent field magnets
102
secured inside the yoke
101
; a shaft
104
disposed inside the yoke
101
by means of bearings
103
so as to be able to rotate freely; an armature
105
secured to the shaft
104
; a commutator
106
secured to an end portion of the shaft
104
; and brushes
108
held by brush holders
107
contacting the surface of the commutator
106
by the elastic force of springs (not shown).
The armature
105
comprises: a core
109
having a plurality of slots
110
extending longitudinally; and windings
111
constructed by winding wire into the slots
110
by a lap winding method.
The above hollow, cylindrical commutator
106
is provided with a plurality of copper segments
112
arranged with even pitch, and mica (not shown) disposed between the segments
112
for electrically insulating adjacent segments
112
.
In the above
4
-pole lap-wound commutator motor
100
, an electric current is supplied to the windings
111
from outside by means of the brushes
108
contacting the segments
112
, whereby the armature
105
rotates together with the shaft
104
due to electromagnetic action.
In a commutator motor
100
of the first construction above, mica is interposed between the segments
112
, forcing the commutator motor
100
to be enlarged. For that reason, there are commutator motors aiming to reduce size by eliminating the mica.
FIG. 17
is a front cross-section of a commutator motor
113
of a commutator motor of a second construction. As shown in
FIG. 18
, the commutator
113
is formed by integrating an insulating resin portion
114
and an annular portion
115
composed of copper by insertion molding, then cutting a plurality of spaces
116
longitudinally in the outer surface of the annular portion
115
. In other words, the commutator
113
is formed such that spaces
116
are formed between the segments
117
and the segments
117
are arranged with even pitch circumferentially.
In a commutator motor of the second construction above, all of the segments
117
of the commutator
113
are held by the insulating resin portion
114
, but when the cutting precision is insufficient, irregularities occur in the width W of the segments
117
and in the dimensions L of the spaces between the segments
117
. Then, as shown in
FIG. 19
, for example, where three segments
117
should normally contact the first brush
108
A and the third brush
108
C and two segments
117
should normally contact the second brush
108
B and the fourth brush
108
D, for just an instant only two segments
117
a
,
117
x
(the first and twenty-second) contact the first brush
108
A. As a result, where the number of coils
118
in this case should normally be evenly distributed at four for each of the first to fourth circuits
119
a
to
119
d
between the first to fourth brushes
108
A to
108
D, a different number arises. That is to say, the first coil
118
a
to the fifth coil
118
e
are interposed in the first circuit
119
a
, making five interposed coils
118
. Consequently, where the current A flowing through the first circuit
119
a
should normally have the same value as the current B flowing through the third circuit
119
c
, a different value arises. As a result, a problem has been that the balance of electromagnetic attraction acting on the armature
105
is lost, giving rise to excitation in the armature
105
and generating operating noise.
Besides requiring highly precise cutting of the annular portion
115
in order to avoid problems of deviation in the commutation timing resulting from the above sort of irregularities in cutting precision, as shown in
FIG. 20
, in order to prevent the brushes
108
from shifting around the circumference of the commutator
113
, the clearance between the brushes
108
and the brush holders
107
is made as small as possible, and for that reason friction arises between the brushes
108
and the brush holders
107
, and so a problem has been that in order to overcome that frictional force and place the brushes
108
in contact with the segments
117
, the force pressing against the brushes
108
must be large, increasing torque loss.
SUMMARY OF THE INVENTION
The present invention aims to solve the above problems and an object of the present invention is to provide a commutator motor enabling reductions in operating noise, as well as reducing the force pressing on the brushes and reducing torque loss.
To this end, according to the present invention, there is provided a commutator motor comprising: a yoke; a magnetic field portion secured to the inner wall of the yoke; a shaft disposed within the yoke so as to be able to rotate freely; an armature secured to the shaft having windings constructed by winding wire by a lap-winding method into slots formed on the outer circumferential surface of a core so as to extend longitudinally; a commutator secured to the shaft including a hollow cylindrical insulating resin portion and a plurality of segments held on an outer circumferential portion of the insulating resin portion with spaces between adjacent segments being held by the insulating resin portion; a plurality of brushes contacting the surface of the commutator; and a equalizing member electrically connecting segments which are to have the same electric potential.


REFERENCES:
patent: 3535776 (1970-10-01), Luca
patent: 4396850 (1983-08-01), Herr
patent: 4490637 (1984-12-01), Van De Griend
patent: 6057623 (2000-05-01), Tanka et al.
patent: 6057626 (2000-05-01), Tanaka et al.
patent: 56-149565 (1955-04-01), None
patent: 59-86847 (1984-06-01), None
patent: 1-120767 (1989-08-01), None

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