DC brush motor

Details DC brush motor DC brush motor

2000-09-18

2003-05-13

Lam, Thanh (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S089000, C310S233000, C310S239000

Reexamination Certificate

active

06563245

ABSTRACT:

This application is based on and claims priority under 35 U.S.C. §119 with respect to Japanese Patent Application No. 11(1999)-262603 filed on Sep. 16, 1999, the entire content of which is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention generally relates to a motor. More particularly, the present invention pertains to a DC brush motor used as a driving source in applications such as a vehicular window regulator, power operated seat, and ABS (anti-skid brake system).
BACKGROUND OF THE INVENTION
The axial dimension of a DC brush motor depends on the length of the armature made up of a coil winding and a core, the length of the brush or commutator, the length of the bearing, and the gaps that are required between adjacent members forming the motor.
FIG. 11
illustrates an arrangement which makes it possible to shorten the axial length of a DC brush motor. In this motor construction, the out put side of a shaft
61
is supported in a rotatable fashion with respect to a casing
62
and a cover
73
by way of respective bearings
63
a
,
63
b
. The bearing
63
b
and a commutator
65
are positioned at opposite sides of an armature
64
. To shorten the axial length of the DC brush motor, the bearing
63
b
and a portion of the commutator
65
are placed inside a coil winding
66
of the armature
64
. A brush
67
and a brush supporting member
68
are disposed between one end of the armature
64
and the output side cover
73
.
FIG. 12
illustrates a motor similar to that disclosed in Japanese Patent Laid-Open Publication No. Hei. 10 (1998)-248225. In this motor, a commutator
65
is disposed inside an armature
64
and a brush
67
is disposed inside the armature
64
so as to be movable in parallel with a shaft
61
. The brush
67
is accommodated within a plurality of brush holders
68
b
which project in the axial direction of the armature
64
toward a disc-shaped main body
68
a
. The brush
67
is urged by a spring
69
to be in contact with a contact portion
65
a
of the commutator
65
a.
FIG. 13
illustrates another motor similar to that disclosed in Japanese Patent Laid-Open Publication No. Hei. 10 (1998)-174360. This electric motor is used as a driving source for an automotive ABS system. The motor includes a shaft
61
having opposite ends rotatably supported by respective bearings
63
a
,
63
b.
An output transmitting member
70
is positioned at a side of the bearing
63
a
, and a bearing
72
is provided on the output transmitting member
70
for converting rotational movement of the shaft
61
into reciprocating movement of a plunger
71
.
With the motor construction shown in
FIG. 11
, the motor still possesses an axial length necessary for accommodating the brush
67
and the brush supporting member
68
, thus making it difficult to make the motor smaller or thinner.
With the motor construction shown in
FIG. 12
, although the commutator
65
and the brush
67
can be inside the range defined or limited by the axial length of the armature
64
, the bearing
63
a
cannot be placed inside the armature
64
due to the existence of the disc-shaped main body
68
a
between the bearing
63
a
and the brush
67
. As a result, limitations are placed on the ability to make the motor smaller. In addition, with this structure, the contact portion or segment
65
a
is sector-shaped and is placed at just the outer side of the shaft
61
which is a narrow portion, thus making it quite difficult if not impossible to establish a sufficient area of the segment
65
a
, resulting in higher brush current density and thereby raising a problem which increases the brush friction.
With the structure shown in
FIG. 13
, the bearing
72
is placed next to the inside of the bearing
63
a
so that the flexing of the shaft
61
is lessened when compared to placing the bearing
72
next to the outside of the bearing
63
a.
However, in this construction, the bearing
72
has to be isolated from the bearing
63
b
in such a manner that the difference between the two bearings is greater than the sum of the axial lengths of the armature
64
and the commutator. As a result, the span between the bearings
63
b
,
72
is relatively larger, and so a problem arises in that the vibration reduction effect associated with the reduced flexing of the shaft
61
becomes insufficient.
SUMMARY OF THE INVENTION
The present invention provides a DC brush motor that includes an armature having a recessed or concave portion, a pair of bearings rotatably supporting the armature, a brush and a commutator. The brush, the commutator, and one of the bearings located nearer to the brush is accommodated in the recessed portion of the armature so as to be axially positioned within the axial length range of the armature. The axial length of the motor is thus shorter than that of a motor constructed so that the bearings, the brush, and the commutator are positioned outside the armature.
According to another aspect of the invention, a DC brush motor includes an armature, a commutator rotatable together with the armature, and having a brush contact portion oriented in the radially inward direction, and a brush extending in the radially outward direction to contact the brush contact portion of the commutator. With this construction, the accommodating portion in which the brush is accommodated is shorter in the axial extent as compared to a construction in which the brush is positioned to be movable in the axial direction of the armature.
According to a further aspect of the invention, A DC brush motor includes an armature having a cup-shaped or concave portion, a pair of bearings rotatably supporting the armature, and a commutator rotatable together with the armature. The commutator has a brush contact portion oriented radially inwardly, and a brush extends radially outwardly to contact the brush contact portion of the commutator. The brush, the commutator, and one of the bearings located nearer to the brush are accommodated in the cup-shaped or concave portion of the armature so as to be axially positioned within the axial length range of the armature.
The bearings located farther from the brush is at least partly accommodated in the armature so that the bearing located farther from the brush is axially located at least partly in the axial length range of the armature. The core of the armature can be in the form of a molding made of soft magnetic powder material. This increases the flexibility in design of the core shape as compared to an armature made of stacked iron plates (steel plates). In addition, the core possesses improved specific resistance compared to the stacked core, thus lowering the eddy current loss considerably and improving the motor efficiency.
The armature includes a shaft supported by the bearings, wherein the shaft has an eccentric portion formed on an output shaft portion. The eccentric portion is provided with a transmission bearing to transmit rotational movement of the output shaft portion to a driving portion which reciprocates. When the output shaft portion rotates, the resulting rotation is transmitted by way of the transmission bearing mounted on the eccentric portion of the output shaft portion to the driving portion to causes reciprocating movement of the driving portion. Due to the relatively short span between the pair of bearings supporting the shaft of the armature, the flexing of the shaft is relatively small when a radial force is applied to the shaft by way of the transmission bearing. In addition, the transmission bearing is placed inside the bearing which supports the armature. This reduces the flexing of the shaft when a radial force is applied to the shaft by way of the transmission bearing.


REFERENCES:
patent: 3870914 (1975-03-01), Walker
patent: 5250862 (1993-10-01), Uzawa
patent: 5434463 (1995-07-01), Horski
patent: 5528096 (1996-06-01), Orii et al.
patent: 5614775 (1997-03-01), Horski et al.
patent: 5821662 (1998-10-01), Kajino et al.
patent: 5866961 (1999-02-01), Suzuki et al.
patent: 5949174 (1999-09-01), Moss et al.
patent: 2062973 (1981-

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