U.S. patent application number 10/161608 was filed with the patent office on 2003-02-06 for disc-type commutator for electric rotating machine.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Ebihara, Jiro, Ito, Akiyasu, Ohta, Hajime.
Application Number | 20030025421 10/161608 |
Document ID | / |
Family ID | 19067495 |
Filed Date | 2003-02-06 |
United States Patent
Application |
20030025421 |
Kind Code |
A1 |
Ebihara, Jiro ; et
al. |
February 6, 2003 |
DISC-TYPE COMMUTATOR FOR ELECTRIC ROTATING MACHINE
Abstract
A disc-type commutator is mounted on a rear end surface of an
armature of an electrical rotating machine. Plural commutator
segments are radially arranged around a rotating shaft, separated
from one another by radially extending commutator gaps. A width of
the commutator gap is gradually widened along a radial direction of
the commutator, so that foreign particles, such as swarfs or brush
dusts, entered in the commutator gap are removed by a centrifugal
force generated in rotation of the armature. Further, the width of
the commutator gap may be gradually widened along its depth
direction so that the width becomes wider at its open end that at
its closed end.
Inventors: |
Ebihara, Jiro; (Nukata-gun,
JP) ; Ohta, Hajime; (Anjo-city, JP) ; Ito,
Akiyasu; (Anjo-city, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
DENSO CORPORATION
1-1, Showa-cho
Kariya-city
JP
448-8661
|
Family ID: |
19067495 |
Appl. No.: |
10/161608 |
Filed: |
June 5, 2002 |
Current U.S.
Class: |
310/237 |
Current CPC
Class: |
H01R 39/06 20130101;
H02K 13/10 20130101; H02K 13/006 20130101 |
Class at
Publication: |
310/237 |
International
Class: |
H02K 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 3, 2001 |
JP |
2001-236170 |
Claims
What is claimed is:
1. A disc-type commutator for an electric rotating machine
comprising: an insulating disc fixed to a rotating shaft of the
electric rotating machine; a plurality of commutator segments
disposed in contact with the insulating disc, each commutator
segment being aligned to extend in a radial direction thereby
forming a disc-shaped commutating surface which is perpendicular to
an axial direction of the rotating shaft; and a segment gap formed
between side surfaces of neighboring commutator segments, one end
of the segment gap in the axial direction being open to the
commutating surface and the other end being closed by the
insulating disc, wherein: a width of the segment gap in a rotating
direction of the commutator is gradually widened along a radial
direction of the commutator so that the width is the narrowest at a
radial inside and the widest at an radial outside of the
commutator.
2. A disc-type commutator for an electric rotating machine
comprising: an insulating disc fixed to a rotating shaft of the
electric rotating machine; a plurality of commutator segments
disposed in contact with the insulating disc, each commutator
segment being aligned to extend in a radial direction thereby
forming a disc-shaped commutating surface which is perpendicular to
an axial direction of the rotating shaft; a segment gap formed
between side surfaces of neighboring commutator segments, one end
of the segment gap in the axial direction being open to the
commutating surface and the other end being closed by the
insulating disc, wherein: the segment gap at its end closed by the
insulating disc is gradually widened toward the commutating surface
by slanting the side surfaces of the commutator segment with
respect to the axial direction of the rotating shaft.
3. The disc-type commutator as in claim 1, wherein: the width of
the segment gap at the radial outside of the commutator is more
than twice of the width at the radial inside.
4. The disc-type commutator as in claim 1, wherein: the segment gap
at its end closed by the insulating disc is gradually widened
toward the commutating surface by slanting the side surfaces of the
commutator segment with respect to the axial direction of the
rotating shaft.
5. The disc-type commutator as in claim 2, wherein: a forward side
surface of the commutator facing a rotating direction of the
commutator is slanted more than a backward side surface with
respect to the axial direction of the rotating shaft.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based upon and claims benefit of
priority of Japanese Patent Application No. 2001-236170 filed on
Aug. 3, 2001, the content of which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a disc-type commutator for
an electric rotating machine.
[0004] 2. Description of Related Art
[0005] A disc-type commutator mounted on an axial end of an
armature of an electric rotating machine such as a fuel pump motor
or a starter motor has been known hitherto. There are two types of
disc-type commutator. One is a separate type which is made
separately from armature conductors and mounted on an armature end
surface. The other is a unitary type which is made integrally with
armature conductors. In those disc-type commutators, commutator
segments are arranged in a radial direction on an axial end surface
of an armature, and segment gaps between commutator segments are
open to the axial end surface that constitutes a commutating
surface. A width of the segment gap is made as narrow as possible
to effectively utilize the commutating surface and to reduce a
current density on the commutating surface.
[0006] By using the disc-type commutator, it is possible to shorten
an axial length of an armature, compared with an armature using an
cylinder-type commutator. However, there has been a problem in the
conventional disc-type commutator. That is, swarfs generated in a
process of machining the commutating surface enter into the segment
gaps that are open to the commutating surface, and it is difficult
to remove those swarfs from the segment gaps. Further, brush dusts
and other foreign particles entered into the segment gaps during
operation of the rotating machine are not easy to remove from the
segment gaps. When the cylinder-type commutator is used, such dusts
or foreign particles can be removed by a centrifugal force
generated by rotation of the armature. It is difficult, however, to
remove the foreign particles from the segment gaps of the disc-type
commutator. If such foreign particles remain in the segment gaps, a
proper insulation between segments cannot be maintained, or
abnormal abrasion of brushes may occur. This may result in
malfunction of the commutator.
SUMMARY OF THE INVENTION
[0007] The present invention has been made in view of the
above-mentioned problem, and an object of the present invention is
to provide an improved disc-type commutator in which foreign
particles entered into the segment gaps are easily removed.
[0008] The disc-type commutator is composed of an insulating disc
and plural commutator segments radially disposed on the insulating
disc, forming a commutating surface. The commutator segments are
separated from one another by segment gaps formed between
neighboring commutator segments. The disc-type commutator is
mounted on a rear end surface of an armature of an electric
rotating machine so that the commtator surface is positioned
perpendicularly to a rotating axis of the armature. Conductors
forming an armature coil disposed in slots of an armature core are
electrically connected to the commutator segments. One end of the
segment gaps in the axial direction is open to the commutating
surface and the other end is closed by the insulating disc.
[0009] A width of the segment gap in a rotational direction of the
armature is narrow at the radial inside of the commutator and
gradually widened toward the radial outside. The width may be made
more than twice wider at the radial outside than at the radial
inside. Swarfs entered into the segment gaps in a process of
machining the commutating surface and foreign particles such as
brush dusts entered during operation of the rotating machine are
easily removed from the segment gaps by a centrifugal force
generated by rotation because the segment gaps are widened at the
radial outside.
[0010] Further, the width of the segment gap is gradually widened
along the axial direction, so that the segment gap is the narrowest
at its closed end contacting the insulating disc and the widest at
its end open to the commutating surface. The segment gap may be
widened symmetrically with respect to the axial direction, or
asymmetrically widened by making a forward side surface of the
commutator segement facing the rotational direction slanted more
than a backward side surface.
[0011] According to the present invention foreign particles such as
swarfs or brush dusts entered into the segment gaps can be easily
removed, and thereby commutator functions are properly maintained
for a long time.
[0012] Other objects and features of the present invention will
become more readily apparent from a better understanding of the
preferred embodiment described below with reference to the
following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a perspective view showing an armature using a
disc-type commutator of the present invention;
[0014] FIG. 2 is a plan view showing part of the disc-type
commmutator shown in FIG. 1, viewed from a commutating surface;
[0015] FIG. 3 is an enlarged plan view showing part of the
disc-type commutator shown in FIG. 2;
[0016] FIG. 4 is a cross-sectional view showing a segment gap
formed in the disc-type commutator, taken along line IV-IV shown in
FIG. 3; and
[0017] FIG. 5 is a cross-sectional view showing a modified form of
the segment gap.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0018] A preferred embodiment of the present invention will be
described with reference to FIGS. 1-4. An armature 1 is composed of
a shaft 3, an armature core 11 having plural slots 12, conductors
13 disposed in the slots 12, and a disc-type commutator 2 mounted
on a rear side of the armature. The rear side and the front side
are indicated by arrows in FIG. 1. In each slot 12, two conductors,
an inner conductor and an outer conductor, are disposed. The inner
conductor is positioned at an inside portion of the slot 12 and the
outer conductor is positioned, laminated on the inner conductor, at
an outside portion of the slot 12. Each of the inner and outer
conductors 13 has a rectangular cross-section.
[0019] The outer conductor 13 disposed in one slot 12 is connected
to the inner conductor 13 disposed in another slot 12 which is
apart from the former slot by a predetermined number of slots (a
slot pitch) via a connecting conductor. In other words, the outer
conductor and the inner conductor are connected to each other
through a connecting conductor, forming a pair of conductors in a
U-shape. The number of the pairs of the conductors is the same as
the number of slots 12. The connecting conductors are disposed at
the front end surface of the armature 1, forming an coil end. An
end of the outer conductor 13 extends to the rear surface of the
armature 1 and is connected to an outer end of a commutator segment
21. Similarly, an end of the inner conductor 13 extends to the rear
surface of the armature 1 and is connected to an inner end of the
commutator segment 21. Preferably, the outer conductor 13 and the
commutator segment 21 are integrally formed.
[0020] As shown in FIG. 1, the disc-type commutator 2 is mounted on
the rear side surface of the armature 1. The disc-type commutator 2
is composed of an insulating disc 22 and commuator segments 21
arranged on the insulating disc 22 so that each commutator segment
21 extends in a radial direction, separated from one another by a
segment gap 23. The number of the commutator segments 21 is equal
to the number of the armature slots 12. After the disc-type
commutator 2 is attached to the rear end of the armature 1, an end
collar 4 made of an insulating material is installed on the shaft 3
so that the inner end portions of the commutator segments 21 are
pushed toward the armature core 11. Thus, the disc-type commutator
2 is mounted on the armature 1. Further details of the armature
structure will not be described here because the armature 1 having
the disc-type commutator 2 is generally a know type.
[0021] The rear surface of the disc-type commutator 2 is shown in
FIG. 2. The rear surface of the commutator 2 is machined after the
commutator 2 is mounted on the armature 1 to set the thickness (a
dimension in the axial direction) of the segments 21 to a
predermined dimension and to smoothen the surface. By this
machining a smooth surface functioning as a commutating surface
(hatched area in FIG. 2) is formed. In the machining process,
swarfs enter into the segement gaps 23 together with machining
oil.
[0022] The segment gaps 23 are shaped in the following manner, so
that the swarfs entered into the segment gaps 23 are easily
removed, and brush dusts and foreign particles entering into the
segment gaps 23 during actual use of the commutator 2 do not remain
in the segment gaps 23. As shown in FIG. 3, the segment gap 23 is
not formed in a uniform width. The segment gap 23 having a width
"b" at its inner portion is gradually enlarged so that its width
becomes "a" at its outer portion. In this particular embodiment,
the width "a" is made larger than two times of width "b".
[0023] The swarfs and oil entered into the segment gaps in the
surface machining process can be removed by rotating the armature 1
after the armature 1 is completed, because the swarfs and oil are
moved along the gradually widened segment gaps 23 by the
centrifugal force and are removed from the outer periphery of the
commutator 2. Alternatively, water or air is blown at a high speed
to the commutator surface in a direction from its inside to
outside. Since the segment gaps 23 are widened toward the outside,
the swarfs and oil can be easily removed. Further, foreign
particles such as brush dusts entering into the segments gaps 23 in
operation of the rotating machine are automatically removed by a
centrifugal force generated by rotation.
[0024] The segment gap 23 may be formed in a shape shown in FIG. 4.
The segment gap 23 is gradually widened along the axial line of the
commutator 2. That is, a width "t" of the segment gap 23 is narrow
at its bottom end contacting the insulating disc 22 and is
gradually widened toward the commutating surface 210. Since the
segment gap 23 is widened at its open end, the swarfs entered into
the segment gap 23 can be easily removed by rotating the armature 1
or blasting water or air at a high speed. Foreign particles
entering into the segment gaps 23 during operation of the rotating
machine can be automatically removed. The swarfs or the foreign
particles are removed in direction D when the armature 1 rotates in
a direction shown with an arrow in FIG. 4. The shapes of the
segment gap 23 shown in FIGS. 3 and 4 may be applied to the
commutator independently from each other, or both may be applied at
the same time.
[0025] The shape of the segment gap shown in FIG. 4 may be modified
to the form shown in FIG. 5. The segment gap 23 is widened
symmetrically with respect to the axial direction perpendicular to
the commutating surface in the example shown in FIG. 4. In FIG. 5,
however, the segment gap 23a is asymmetrically widened with respect
to the axial direction. That is, a forward side surface 211 of the
commutator segment 21a facing a rotational direction is slanted
more, with respect to the axial line, than a backward surface 212.
The swarfs or the foreign particles in the segment gaps 23a can be
removed in direction D. In this manner, the segment gap 23a can be
widened while minimizing the commutating surface 210 sacrificed by
the widened gap.
[0026] The present invention is equally applicable to the disc-type
commutator in which the commutator segments 21 are formed
integrally with the conductors 13 and to the disc-type commutator
which is made separately from the conductors 13.
[0027] While the present invention has been shown and described
with reference to the foregoing preferred embodiment, it will be
apparent to those skilled in the art that changes in form and
detail may be made therein without departing from the scope of the
invention as defined in the appended claims.
* * * * *