Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-11-15
2001-12-11
Waks, Joseph (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S089000
Reexamination Certificate
active
06329735
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a commutator motor used as a motor for an electric power steering assembly for assisting the steering force of an automotive steering wheel, for example.
2. Description of the Related Art
FIG. 10
is a perspective showing use of a motor for an electric power steering assembly which is a conventional commutator motor. This commutator motor
1
is connected to a gear box
3
mounted to the end of a column
2
.
FIG. 11
is a lateral section of the commutator motor
1
. This commutator
1
includes: a cylindrical yoke
4
; 4-pole magnets
6
disposed opposite each other inside the yoke
4
and held by a magnet holder
5
shown in
FIG. 12
; a shaft
9
supported at one end by a first bearing
8
housed in a bearing housing portion
7
of the yoke
4
so as to rotate freely; an armature
10
secured to the shaft
9
; a commutator
11
secured to one end of the shaft
9
; brushes
13
placed in contact with the surface of the commutator
11
by the elastic force of springs
12
; a brush holder
14
for holding the brushes
13
; a housing
16
integrated with the yoke
4
by a bolt
15
; a bolt
17
securing the brush holder
14
to the housing
16
by means of an elastic body
100
which is rubber; a second bearing
18
secured to a central portion of the housing
16
for supporting the other end of the shaft
9
so as to rotate freely; and a grommet
21
through which a lead wire
20
passes connected by welding to metal fittings (not shown) whose tips are insertion molded into the brush holder
14
.
The armature
10
includes: a core
22
having a plurality of slots extending in the axial direction; and a winding
23
constructed by winding wire into the slots by a lap-winding method.
The magnet holder
5
includes: four stanchion portions having a plurality of protrusions
31
for holding the magnets
6
; and an engaging portion
32
formed on a radially inner portion of the magnet holder for engaging a recess (not shown) in the brush holder
14
.
In a commutator motor
1
of the above construction, the armature
10
is rotated together with the shaft
9
due to electromagnetic action by supplying electric current from the lead wire
20
to the winding
23
by means of the brushes
13
contacting the commutator segments
11
. The torque of the shaft
9
is transmitted to a shaft
24
spline fitted to a boss
19
secured to the shaft
9
, and serves to assist the steering force acting on the steering wheel
25
.
The commutator motor
1
is mounted to a mounting seat
33
close to the vehicle cab, requiring strict noise prevention. Vibrations transmitted from the gear box
3
side are transmitted through the shaft
24
and the housing
16
to the brush holder
14
, which causes the brushes
13
to vibrate, giving rise to brush noise, and the brush holder
14
is also supported on the housing
16
by means of the elastic body
100
in order to prevent the sliding noise of the brushes
13
from being transmitted from the brush holder
14
through the housing
16
to the gear box
3
side or to the yoke
4
. That is to say, the brush holder
14
is rubber mounted.
However, in a commutator motor
1
of the above construction, one problem has been that since the lead wire
20
passes through the grommet
21
and extends outside as shown in
FIG. 13
, the brush holder
14
held by the elastic body
100
may be displaced from center or be tilted relative to the shaft
9
by movement of the lead wire
20
which is connected to the metal fittings inside the brush holder or during installation of the brush holder
14
, making contact between the brushes
13
and the commutator
11
uneven, causing the performance of the commutator motor
1
to deteriorate (for example, rotational frequency and rotational torque may be different in the clockwise and counterclockwise directions), and shortening the working life of the brushes
13
and increasing brush noise. This problem is particularly serious in the case of a motor for an electric power steering assembly which rotates in both directions.
Another problem has been that although the brush holder
14
is supported on the housing
16
by means of the elastic body
100
, because the brush holder
14
is positioned by the engaging portion
32
of the magnet holder
5
, vibrations from outside, for example, may be transmitted to the brush holder
14
through the yoke
4
, the magnets
6
, and the magnet holder
5
, which causes the brushes
13
to vibrate, giving rise to brush noise.
An additional problem has been that because the first bearing
8
is housed in the bearing housing portion
7
of the yoke
4
, if there is any clearance between the bearing housing portion
7
and the first bearing
8
, the first bearing
8
may knock against the inner wall of the bearing housing portion
7
when the armature
10
rotates, giving rise to impact noises, and brush noise may increase due to rattling of the armature
10
.
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 prevention of displacement of a brush holder held in a housing by means of an elastic body, reductions in noise, and further improvements to the effectiveness of the rubber mount for the brush holder.
To this end, according to the present invention, there is provided a commutator motor comprising: a cylindrical yoke; magnets disposed opposite each other inside said yoke; a shaft disposed on the central axis of the yoke so as to rotate freely; an armature secured to the shaft; a commutator secured to one end of the shaft; brushes placed in contact with the surface of the commutator by the elastic force of springs; a brush holder for holding the brushes; and a housing mounted to the yoke, the brush holder being supported on the housing by means of an elastic body, and an elastic member for positioning the central axis of the brush holder so as to be aligned with the central axis of the shaft being disposed between the housing and the brush holder.
REFERENCES:
patent: 3898493 (1975-08-01), Schaffer
patent: 4538085 (1985-08-01), Tanaka
patent: 4629024 (1986-12-01), Buike et al.
patent: 4707630 (1987-11-01), Tomite et al.
patent: 5015897 (1991-05-01), Inagaki et al.
patent: 5810111 (1998-09-01), Takeuchi et al.
patent: 2621750A3 (1988-10-01), None
patent: 2004130A (1979-03-01), None
patent: 2154375A (1985-09-01), None
patent: 7-21085 (1995-05-01), None
patent: 09215254A (1997-08-01), None
Takashima Kazuhisa
Tanaka Toshinori
Yamamoto Kyouhei
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
Waks Joseph
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