Alternator

Details Alternator Alternator

2000-09-20

2002-07-23

Mullins, Burton S. (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S180000, C310S254100, C310S179000

Reexamination Certificate

active

06424073

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an alternator in which alternating voltage is generated in a stator by rotation of a rotor.
2. Description of the Related Art
In recent years, there has been an increasing demand for an automotive alternator that generates more power because of increasing vehicular load, whereas a mounting space therefore is decreasing because of a trend toward a smaller vehicular engine room.
In addition, there has been another increasing demand for reduced noises both inside and outside a vehicle, and engine noises are being decreased to respond to such a demand. A noise of an automotive alternator, which constantly operates to generate power to supply electrical load to a vehicle, has been a problem to be solved in achieving reduced noises. In the automotive alternator rotationally driven over a relatively wide revolution region from low speed to high speed, a wind noise or an electromagnetic noise thereof has been a topic to be tackled. Especially high-frequency wind noises or electromagnetic noises in a low engine speed region to a normal working region have been posing a problem because they sound particularly uncomfortable to the ears, having different frequencies from those of noises of other engine or engine accessories.
FIG. 14
is a sectional view of a conventional automotive alternator (hereinafter referred to simply as “alternator”),
FIG. 15
is a perspective view of a rotor of
FIG. 14
,
FIG. 16
shows a stator of
FIG. 14
(a lead wire and a neutral wire of a stator winding are not shown), and
FIG. 17
is an electrical circuit diagram of the alternator of FIG.
14
.
The alternator includes: a case
3
composed of an aluminum front bracket
1
and an aluminum rear bracket
2
; a shaft
6
rotatably disposed in the case
3
and which has a pulley
4
secured to one end thereof; a Lundell-type rotor
7
secured to the shaft
6
; fans
5
secured to both axial ends of the rotor
7
; a stator
8
secured to an inner wall of the case
3
; a slip ring
9
secured to the other end of the shaft
6
and which supplies electric current to the rotor
7
; a brush
10
that slides in contact with the slip ring
9
; a brush holder
11
accommodating the brush
10
; a first rectifier
12
a
and a second rectifier
12
b
electrically connected to the stator
8
to convert alternating current generated in the stator
8
into direct current; a heat sink
17
fitted on the brush holder; and a regulator
18
adhesively fastened to the heat sink
17
and which adjusts a magnitude of an alternating voltage generated in the stator
8
.
The rotor
7
is equipped with a field winding
13
for generating magnetic flux by passing an electric current, and a pole core
51
covering the field winding
13
in which magnetic poles are produced by the magnetic flux. The pole core
51
has a pair of a first pole core assembly
20
and a second pole core assembly
21
that intermesh with each other. The first pole core assembly
20
and the second pole core assembly
21
are made of iron and have claw-shaped magnetic poles
22
and
23
at their ends. Spaces
50
are formed between adjacent claw-shaped magnetic poles
22
and
23
to prevent magnetic flux from leaking from between the claw-shaped magnetic poles
22
and
23
, and also to function as cooling passages for cooling the field winding
13
.
The stator
8
is provided with a stator core
15
and a stator winding
16
. The stator winding
16
has two windings, namely, a first three-phase stator winding
52
and a second three-phase stator winding
53
, in which conductors are wound onto the stator core
15
with a phase difference of a 30-degree electrical angle.
The stator core
15
shown in
FIG. 18
is formed by punching steel sheet into a comb-like plate with equidistantly arranged teeth, and by winding or laminating the comb-like plate into an annular shape. The stator core
15
has an annular core back
55
, and a plurality of teeth
54
in which a plurality of slots
15
a
and openings
15
b
are formed, the slots
15
a
and the openings
15
b
radially extending inward from the core back
55
and being disposed equidistantly in a circumferential direction.
In this example, the stator core
15
includes the two windings, namely, the first three-phase stator winding
52
and the second three-phase stator winding
53
, and the rotor
7
has sixteen magnetic poles with two three-phase portions corresponding to each pole. There are
96
slots
15
a
, openings
15
b
, and teeth
54
, which are formed at regular pitches of 3.75-degree mechanical angles.
The first three-phase stator winding
52
and the second three-phase stator winding
53
have a front coil end
16
a
and a rear coil end
16
b
respectively projecting from both end surfaces of the stator core
15
. The coil ends
16
a
and
16
b
are composed of a plurality of extending portions
30
a
, which are heat radiating portions. The extending portions
30
a
having the same shape are arranged orderly in a circumferential direction in two rows apart from each other in a radial direction.
FIG. 19
shows a winding structure of a stator winding
56
for one phase of the three-phase stator windings
52
and
53
. In the drawing, dark dots in circles in the slots
15
a
of the stator
15
denote conductors
30
that extend from the front bracket
1
to the rear bracket
2
, and cross marks (x) in the circles in the slots
15
a
of the stator
15
denote the conductors
30
that extend from the rear bracket
2
to the front bracket
1
.
The stator winding
56
for the one phase is formed of the copper conductors
30
, each of which has its outer surface coated with enamel. The conductors
30
of the first three-phase stator winding
52
are wave-wound at every six slots from slot No.
1
to slot No.
91
. In each slot
15
a
, the conductors
30
are radially arranged in four layers in one row. In the stator windings for the remaining two phases of the first three-phase stator winding
52
, the conductors
30
are wave-wound at every six slots from slot Nos.
3
to
93
, and slot Nos.
5
to
95
, respectively, and the conductors
30
are radially arranged in four layers in one row in each slot
15
a.
The conductors
30
of the second three-phase stator winding
53
are wave-wound at every six slots from slot No.
2
to slot No.
92
. In each slot
15
a
, the conductors
30
are radially arranged in four layers in one row. In the stator windings for the remaining two phases of the second three-phase stator winding
53
, the conductors
30
are wave-wound at every six slots from slot Nos.
4
to
94
, and slot Nos.
6
to
96
, respectively, and the conductors
30
are radially arranged in four layers in one row in each slot
15
a.
Furthermore, as shown in
FIG. 17
, the stator windings
56
for the three phases are star-connected to form the first three-phase stator winding
52
, and the additional stator windings
56
for the three phases are also star-connected to form the second three-phase stator winding
53
. The three-phase stator windings
52
and
53
are provided in the slots
15
a
with a phase difference of a 30-degree electrical angle from each other, and are electrically connected to the first rectifier
12
a
and the second rectifier
12
b
, respectively. Direct current outputs of the rectifiers
12
a
and
12
b
are connected in parallel and combined.
In an automotive alternator of the above construction, current is supplied by a battery (not shown) through the brush
10
and slip ring
9
to the field winding
13
so as to generate magnetic flux, whereby the claw-shaped magnetic poles
22
of the first pole core assembly
20
are polarized with north-seeking (N) poles, while the claw-shaped magnetic poles
23
of the second pole core assembly
21
are polarized with south-seeking (S) poles.
The pulley
4
is rotated by an engine, and the rotor
7
rotates together with the shaft
6
. This causes a rotating magnetic field to be imparted to the three-phase stator windings
52
and
53
, and an ele

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