Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-11-30
2003-05-20
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S254100, C310S049540, C310S045000, C310S180000, C310S201000
Reexamination Certificate
active
06566781
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a stator for an automotive alternator, and in particular, relates to a stator for an automotive alternator which is constructed by laminating steel plates.
2. Description of the Related Art
FIG. 6
is a cross section of a conventional automotive alternator,
FIG. 7
is an overall perspective of a stator core in
FIG. 6
, and
FIG. 8
is an overall perspective of a stator in FIG.
6
.
This automotive alternator includes: a case
3
composed of an aluminum front bracket
1
and an aluminum rear bracket
2
; a rotating shaft
6
disposed within the case
3
having a pulley
4
secured to a first end thereof; a Lundell-type rotor
7
secured to the rotating shaft
6
; fans
5
secured to first and second axial end surfaces of the rotor
7
; a stator
8
secured to an inner wall within the case
3
; slip rings
9
secured to a second end of the rotating shaft
6
for supplying electric current to the rotor
7
; a pair of brushes
10
sliding on surfaces of the slip rings
9
; brush holders
11
accommodating the brushes
10
; a rectifier
12
electrically connected to the stator
8
for converting alternating current generated in the stator
8
into direct current; and a regulator
18
fitted over the brush holder
11
for adjusting the magnitude of the alternating voltage generated in the stator
8
.
Air intake openings
3
a
for sucking cooling air into the case
3
and air discharge openings
3
b
for expelling the cooling air to the outside by rotation of the fans
5
are formed in the case
3
.
The rotor
7
includes a rotor coil
13
for generating magnetic flux by passing an electric current, and a pole core
14
disposed so as to cover the rotor coil
13
, magnetic poles being formed in the pole core
14
by the magnetic flux. The pole core
14
is constituted by a first pole core body
21
and a second pole core body
22
which intermesh with each other. The first pole core body
21
and the second pole core body
22
are made of iron and include tapered first and second claw-shaped magnetic poles
23
and
24
.
The stator
8
is constituted by a stator core
15
for passage of a rotating magnetic field from the rotor
7
, and a stator coil
16
constructed by winding wires into the stator core
15
, an output current flowing through the stator coil
16
.
The above stator core
15
is constituted by a base portion
30
having notches
48
on an outer circumferential portion, and a plurality of tooth portions
31
which protrude radially inwards from the base portion
30
. Slots
32
are formed between adjacent tooth portions
31
, and wires are wound continuously into the slots
32
.
FIG. 9
is a diagram showing the stator core
15
during manufacture. The stator core
15
is manufactured from a straight strip-shaped steel plate
35
, which is stamped so as to have a frame portion
37
and a plurality of tooth segments
34
at an even pitch, by laminating and bending the steel plate
35
into a helical shape such that tips of the tooth segments
34
point towards a center. In this example, the stator core
15
is bent and formed by inserting shaping pins
36
into the slots
32
. The laminated steel plate
35
, which has a thickness of 0.5 mm, is integrated by laser welding at eight places on the outer circumferential portion.
In the automotive alternator described above, electric current is supplied from a battery (not shown) through the brushes
10
and the slip rings
9
to the rotor coil
13
, generating magnetic flux. The claw-shaped magnetic poles
23
of the first pole core body
21
are magnetized with north-seeking (N) poles by this magnetic flux, and the claw-shaped magnetic poles
24
of the second pole core body
22
are magnetized with south-seeking (S) poles. At the same time, because the engine is driven by the pulley
4
and the rotor is rotated by the rotating shaft
6
, a rotating magnetic field is applied to the stator core
15
, generating electromotive force in the stator coil
16
. This alternating electromotive force passes through the rectifier
12
and is converted into direct current, the magnitude of the current is adjusted by the regulator
18
, and the battery is recharged.
As described above, the cooling air flow generated by the fans
5
is sucked in through the air intake openings
3
a
formed in the front-end and rear-end brackets
1
and
2
, passing in close proximity to and cooling the rectifier
12
and the regulator
18
which are heat-generating portions at a rear end of the alternator, then passes from a radially inner side to a radially outer side between fan blades
5
a
at both the rear end and a front end, thereby cooling front-end coil ends
16
a
and rear-end coil ends
16
b
of the stator coil
16
before being expelled through the air discharge openings
3
b.
In other words, a high degree of heat is generated but the coil ends of the stator coil
16
whose output performance is affected by high temperatures are constructed so as to be reliably cooled by positioning them between the fan blades
5
a
and the air discharge openings
3
b
on the brackets
1
and
2
.
In the automotive alternator of the above construction, the stator coil
16
has three phases, the rotor
7
has twelve magnetic poles, and the slots
32
are formed at a ratio of one per pole per phase, the total number of slots
32
being thirty-six.
Now, as disclosed in Japanese Patent Laid-Open No. HEI 4-26345, for example, a stator core is known which is formed with slots at a ratio of two per pole per phase with the aim of providing an automotive alternator in which output voltage is improved and voltage fluctuations are reduced by making an overlapping portion between the claw-shaped magnetic poles of the rotor and the tooth portions of the stator core as small as possible to reduce magnetic flux leakage through the tooth portions and reduce ripples in the rectified output voltage. For example, when the number of phases in the stator coil is three and the number of poles in the rotor is twelve, the total number of slots
41
in a stator core
40
is seventy-two, as shown in FIG.
10
.
Because opening portions
42
of the slots
41
become narrow when the number of the slots
41
in the stator core
40
is seventy-two, it is difficult to continuously wind wires of a stator coil from a radially inner side of the stator core
40
through the opening portions
42
.
A technical means for solving such difficulties is disclosed in Japanese Patent No. 2927288.
FIG. 11
is a partial front elevation of a stator
44
in which a stator coil
43
has been mounted to the stator core
40
without difficulty using this technical means even though the number of the slots
41
in the stator core
40
is seventy-two.
This stator coil
43
is constituted by a plurality of electrical conductors
45
, such as the one shown in FIG.
12
. This electrical conductor
45
is constituted by first and second straight portions
46
and a turn portion
47
connecting the straight portions
46
to each other. The first straight portions
46
of the electrical conductors
45
are positioned on a radially inner side being on the opening portion
42
side in a radial direction of first slots
41
to form an inner layer, and the second straight portions
46
of the electrical conductors
45
are positioned on a radially outer side in a radial direction of second slots
41
to form an outer layer.
The electrical conductors
45
are inserted into the slots
41
from a first end surface of the stator core
40
and are stacked up on top of each other such that the turn portions
47
thereof line up in rows. The straight portions
46
on the inner layer and the outer layer which protrude at a second end surface of the slots
41
are bent in a circumferential direction of the stator core
40
, and are connected in series to the straight portions
46
in a different layer of the electrical conductors
45
a distance of one pole away, forming the stator coil
43
.
FIG. 13
is a partial perspective of an end surface
Adachi Katsumi
Asao Yoshihito
Oohashi Atsushi
Mitsubishi Denki & Kabushiki Kaisha
Mullins Burton S.
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