Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-09-28
2004-02-10
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S254100, C310S263000
Reexamination Certificate
active
06690099
ABSTRACT:
This application is based on Application No. 2001-7924, filed in Japan on Jan. 16, 2001, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automotive alternator and particularly to an automotive alternator in which cooling of a stator is improved by making cooling airflows flow through cooling airflow ventilation channels formed by coil end groups of a stator winding and tooth portions of a stator core.
2. Description of the Related Art
FIG. 22
is a cross section showing a conventional automotive alternator,
FIG. 23
is a perspective showing a stator used in the conventional automotive alternator,
FIG. 24
is a schematic diagram explaining a method for manufacturing a conventional stator core, and
FIG. 25
is a plan showing the conventional stator core.
In
FIGS. 22 and 23
, the conventional automotive alternator includes: a case
3
constituted by an aluminum front bracket
1
and an aluminum rear bracket
2
; a shaft
6
disposed inside the case
3
, a pulley
4
being secured to a first end of the shaft
6
; a Lundell-type rotor
7
secured to the shaft
6
; cooling fans
5
secured to first and second axial end portions of the rotor
7
; a stator
8
secured to the case
3
so as to envelop the rotor
7
; slip rings
9
secured to a second end of the shaft
6
for supplying electric current to the rotor
7
; a pair of brushes
10
sliding on surfaces of the slip rings
9
; a brush holder
11
accommodating the brushes
10
; a rectifier
12
having a rectifier heat sink
12
a,
the rectifier
12
being electrically connected to the stator
8
for converting alternating current generated in the stator
8
into direct current; and a regulator
18
mounted to a regulator heat sink
17
fitted onto the brush holder
11
, the regulator
18
adjusting the magnitude of the alternating voltage generated in the stator
8
.
The rotor
7
is constituted by: a field winding
13
for generating magnetic flux on passage of an electric current; and a pair of first and second pole cores
20
and
21
disposed so as to cover the field winding
13
, magnetic poles being formed in the first and second pole cores
20
and
21
by magnetic flux generated in the field winding
13
. The pair of first and second pole cores
20
and
21
are made of iron, each has a plurality of first and second claw-shaped magnetic poles
22
and
23
having a generally trapezoidal outermost diameter surface shape disposed on an outer circumferential edge portion at even angular pitch in a circumferential direction so as to project axially, and the first and second pole cores
20
and
21
are fixed to the shaft
6
facing each other such that the first and second claw-shaped magnetic poles
22
and
23
intermesh.
The stator
8
is constituted by: a cylindrical stator core
15
in which slots
33
extending parallel to an axial direction are arranged at an even angular pitch in a circumferential direction; and a stator winding
16
installed in the slots
33
of the stator core
15
. The stator winding
16
is constituted by three wave-winding phase portions each formed by installing a conductor wire
29
, functioning as an electrical conductor composed of a copper wire material having a circular cross section coated with electrical insulation, into a wave shape in every third slot
33
. The wave-winding phase portions are each installed in the stator core
15
such that the slots
33
in which each wave-winding phase portion is installed are offset by one slot from those of each of the other wave-winding phase portions. In addition, the wave-winding phase portions are each formed by winding the conductor wire
29
into a distributed winding. The stator
8
is held between the front bracket
1
and the rear bracket
2
so as to form a uniform air gap between outer circumferential surfaces of the first and second claw-shaped magnetic poles
22
and
23
and an inner circumferential surface of the stator core
15
.
Moreover, the number of magnetic poles in the rotor
7
is twelve, and there are thirty-six slots
33
formed in the stator core
15
. In other words, the slots are formed at a ratio of one per phase per pole. The stator winding
16
is formed into a three-phase alternating-current winding by forming the three wave-winding phase portions into an alternating-current connection (a Y connection, for example).
A method for manufacturing the stator core
15
will now be explained with reference to FIG.
24
.
First, a long magnetic steel plate
30
is supplied to a pressworking machine (not shown), and formed into tooth portions
30
a
and a base portion
30
b.
Then, the magnetic steel plate
30
is supplied to a core manufacturing device (not shown). Here, the magnetic steel plate
30
is bent and wound up into a helical shape by intermeshing pins
34
in gaps
30
c
defined by the tooth portions
30
a,
and the base portion
30
b.
as shown in FIG.
24
. The magnetic steel plate
30
is laminated to a predetermined thickness and then cut. Outer circumferential portions of the magnetic steel plate wound up in this manner are welded to obtain the stator core
15
shown in FIG.
25
. Here, the tooth portions
30
a
and the base portion
30
b
are each stacked up in the wound magnetic steel plate
30
in the direction of lamination.
As shown in
FIG. 25
, the stator core
15
manufactured in this manner includes: a cylindrical base portion
32
; tooth portions
31
each extending from an inner circumferential surface of the base portion
32
toward an axial center; and the slots
33
, which are defined by the base portion
32
and adjacent pairs of the tooth portions
31
. The tooth portions
31
are disposed at an even angular pitch on the inner circumferential surface of the base portion
32
.
In the conventional automotive alternator constructed in this manner, an electric current is supplied from a battery (not shown) through the brushes
10
and the slip rings
9
to the field winding
13
, generating a magnetic flux. The first claw-shaped magnetic poles
22
on the first pole core
20
are magnetized into North-seeking (N) poles by this magnetic flux, and the second claw-shaped magnetic poles
23
on the second pole core
21
are magnetized into South-seeking (S) poles.
At the same time, the pulley
4
is driven by an engine and the rotor
7
is rotated by the shaft
6
. A rotating magnetic field is applied to the stator core
15
due to the rotation of the rotor
7
, generating an electromotive force in the stator winding
16
. Then, the alternating electromotive force generated in the stator winding
16
is converted into direct current by the rectifier
12
and the magnitude of the output voltage thereof is adjusted by the regulator
18
, recharging the battery.
Now, the field winding
13
, the stator winding
16
, the rectifier
12
, and the regulator
18
are constantly generating heat during power generation, and in an automotive alternator having a rated output current in the 100 A class, the amount of heat generated at rotational frequencies at which the temperature is high is 60 W, 500 W, 120 W, and 6 W, respectively.
Thus, in order to cool the heat generated by power generation, front-end and rear-end air intake apertures
1
a
and
2
a
are disposed through axial end surfaces of the front bracket
1
and the rear bracket
2
, and front-end and rear-end air discharge apertures
1
b
and
2
b
are disposed through radial side surfaces of the front bracket
1
and the rear bracket
2
so as to face coil end groups
16
f
and
16
r
of the stator winding
16
.
Thus, the cooling fans
5
are rotated and driven together with the rotation of the rotor
7
, and cooling airflow channels are formed in which external air is sucked inside the case
3
through the front-end and rear-end air intake apertures
1
a
and
2
a,
flows axially towards the rotor
7
, is then deflected centrifugally by the cooling fans
5
, thereafter crosses the coil end groups
16
f
and
16
r,
and is discharged outside throu
Asao Yoshihito
Oohashi Atsushi
Mitsubishi Denki & Kabushiki Kaisha
Nguyen Tran
Sughrue & Mion, PLLC
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