Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-10-27
2002-07-23
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S063000, C310S184000, C310S201000, C310S263000
Reexamination Certificate
active
06424071
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automotive alternator, and in particular, relates to a construction for coil end groups of a stator winding of the automotive alternator enabling a stator to be cooled efficiently by reducing a flow rate of cooling air flowing through the inside of a rotor.
2. Description of the Related Art
FIG. 5
is a cross section showing a conventional stator for an automotive alternator.
The conventional automotive alternator is constructed by rotatably mounting a Lundell-type rotor
7
by means of a shaft
6
inside a case
3
constituted by an aluminum front bracket
1
and an aluminum rear bracket
2
, and fastening a stator
8
to an inner wall of the case so as to cover an outer circumferential side of the rotor
7
.
The shaft
6
is rotatably supported in the front bracket
1
and the rear bracket
2
. A pulley
4
is fastened to a first end of this shaft
6
so that rotational torque from an engine can be transmitted to the shaft
6
by means of a belt (not shown).
Slip rings
9
for supplying electric current to the rotor
7
are fastened to a second end of the shaft
6
, and a pair of brushes
10
are housed in a brush holder
11
which is disposed inside the case
3
such that the pair of brushes
10
slide in contact with the slip rings
9
. A regulator
18
for adjusting the output voltage generated in the stator
8
is fastened by adhesive to a heat sink
17
fitted onto the brush holder
11
. A rectifier
12
which is electrically connected to the stator
8
and converts alternating current generated in the stator
8
into direct current is mounted inside the case
3
.
The rotor
7
is constituted by a rotor winding
13
for generating magnetic flux on passage of electric current, and a pair of pole cores
20
and
21
disposed so as to cover the rotor winding
13
, magnetic poles being formed in the pole cores
20
and
21
by the magnetic flux generated in the rotor winding
13
. The pair of pole cores
20
and
21
are made of iron, each has a number of claw-shaped magnetic poles
22
and
23
disposed on an outer circumferential perimeter at even pitch in a circumferential direction so as to project axially, and the pole cores
20
and
21
are fastened to the shaft
6
facing each other such that the claw-shaped magnetic poles
22
and
23
intermesh. In addition, fans
5
are fastened to first and second axial ends of the rotor
7
.
The stator
8
is constituted by a stator core
15
, and a stator winding
16
composed by winding a conducting wire into the stator core
15
, an alternating current being generated in the stator winding
16
by changes in the magnetic flux from the rotor
7
accompanying rotation of the rotor
7
.
In the automotive alternator constructed in this manner, electric current is supplied from a battery (not shown) through the brushes
10
and the slip rings
9
to the rotor winding
13
, generating magnetic flux. The claw-shaped magnetic poles
22
of the first pole core
20
are magnetized with north-seeking (N) poles by this magnetic flux, and the claw-shaped magnetic poles
23
of the first pole core
21
are magnetized with south-seeking (S) poles. At the same time, rotational torque from the engine is transmitted through the belt and the pulley
4
to the shaft
6
, rotating the rotor
7
. Thus, a rotating magnetic field is applied to the stator winding
16
, generating electromotive force in the stator winding
16
. This alternating electromotive force passes through the rectifier
12
and is converted into direct current, the output is adjusted by the regulator
18
, and the battery is recharged.
In the automotive alternator, the stator winding
16
, the rectifier
12
, the regulator
18
, etc., constantly generate heat while generating electricity. Thus, in order to cool the heat generated by power generation, front-end and rear-end air intake openings
1
a
and
2
a
and front-end and rear-end air discharge openings
1
b
and
2
b
are disposed in the front bracket
1
and the rear bracket
2
.
At the rear end, a cooling air flow Q
R
is formed by the rotation of the fans
5
, cooling the rectifier
12
, the regulator
18
, and a rear-end coil end group
16
r
of the stator winding
16
. In other words, external air is drawn in by the rotation of the fans
5
through the rear-end air intake openings
2
a
disposed facing both a heat sink
19
on the rectifier
12
and the heat sink
17
of the regulator
18
, cooling the rectifier
12
and the regulator
18
, then passes through fan blades
5
a
from an inner radial side to an outer radial side, cooling the rear-end coil end group
16
r
of the stator winding
16
, and is discharged to the outside through the rear-end air discharge openings
2
b.
At the same time, at the front end, a cooling air flow Q
F
is formed by the rotation of the fans
5
, cooling a front-end coil end group
16
f
of the stator winding
16
. In other words, external air is drawn in by the rotation of the fans
5
through the front-end air intake openings
1
a
in an axial direction, then passes through the fan blades
5
a
from a radially inner side to a radially outer side, cooling the front-end coil end group
16
f
of the stator winding
16
, and is discharged to the outside through the front-end air discharge openings
1
b.
In addition, a cooling air flow Q
Rt
flowing through the inside of the rotor
7
is generated as a result of a pressure difference between the front end and the rear end, cooling the rotor
7
.
Now, because the stator winding
16
generates a high degree of heat, and output properties of the stator winding
16
deteriorate when the temperature is high, the stator winding
16
is constructed so as to enable reliable cooling by positioning the front-end and rear-end coil end groups
16
f
and
16
r
thereof between the fan blades
5
a
and the front-end and rear-end air discharge openings
1
b
and
2
b
, respectively.
Next, the stator winding construction used in the conventional automotive alternator will be explained with reference to FIG.
6
. Moreover,
FIG. 6
is a partial enlargement of the conventional stator viewed from an inner circumferential side.
In
FIG. 6
, the stator core
15
is formed into a cylindrical shape, and a number of slots
15
a
having a groove direction in an axial direction are disposed at even pitch in a circumferential direction so as to open onto the inner circumferential side. The stator winding
16
is constructed by joining together, using arc welding or the like, free end portions
29
c
of coil segments
29
inserted into pairs of slots
15
a
in which the slots
15
a
in each pair are three slots apart, so as to adopt a predetermined winding construction. As shown in
FIG. 7
, each of the coil segments
29
is a short segment of a conductor such as copper or the like having a circular cross section coated with insulation, the conductor being formed into a general U shape composed of a pair of straight portions
29
a
linked by a generally V-shaped turn portion
29
b.
At the front end of the stator core
15
, front-end coil ends
24
formed into a connection pattern composed of pairs of front-end root portions
24
a
extending outwards from pairs of slots
15
a
three slots apart, pairs of front-end inclined portions
24
b
bent from each of the pairs of front-end root portions
24
a
and extending in a circumferential direction, and pairs of front-end joining portions
24
c
connecting together end portions of the pairs of front-end inclined portions
24
b
, are arranged in a circumferential direction to constitute the front-end coil end group
16
f
. Moreover, the front-end joining portions
24
c
correspond to joint portions joining together the free end portions
29
c
of the coil segments
29
.
Similarly, at the rear end of the stator core
15
, rear-end coil ends
25
formed into a connection pattern composed of pairs of rear-end root portions
25
a
extending outwards from pairs of slots
15
a
three slots apart, pairs of rear-end inclined portions
25
Asao Yoshihito
Oohashi Atsushi
Mitsubishi Denki & Kabushiki Kaisha
Mullins Burton S.
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