Alternator

Details Alternator Alternator

2000-10-05

2002-04-02

Ramirez, Nestor (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S043000, C310S045000, C310S051000, C310S064000, C310S208000

Reexamination Certificate

active

06366000

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an alternator driven by an internal combustion engine, for example, and in particular, relates to a stator construction for an automotive alternator mounted to an automotive vehicle such as a passenger car or a truck.
2. Description of the Related Art
FIG. 22
is a cross section showing a conventional automotive alternator, and
FIG. 23
is a perspective showing a stator of the conventional automotive alternator.
In
FIGS. 22 and 23
, the automotive alternator is constructed by rotatably mounting a Lundell-type rotor
7
by means of a shaft
6
inside a case
3
constructed from an aluminum front bracket
1
and an aluminum rear bracket
2
, and fastening a stator
50
to an inner wall of the case
3
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
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 magnitude of alternating voltage generated in the stator
50
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
50
and converts alternating current generated in the stator
50
into direct current is mounted inside the case
3
.
The rotor
7
is composed of a rotor coil
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 coil
13
, magnetic poles being formed in the pole cores
20
and
21
by magnetic flux generated in the rotor coil
13
. The pair of pole cores
20
and
21
are made of iron, each has six 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
50
includes: a cylindrical stator core
51
formed with a number of slots
51
a
extending axially at a predetermined pitch in a circumferential direction; a stator winding
52
wound onto the stator core
51
; electrically-insulative resin portions
25
composed of epoxy resin or the like molded around front-end and rear-end coil ends
52
a
and
52
b
of the stator winding
52
; and insulators (not shown) installed in each of the slots
51
a
for electrically insulating the stator winding
52
from the stator core
51
. In this case
3
, the stator core
51
is formed with thirty-six slots
51
a
at even pitch so as to house one three-phase alternating current winding such that the number of slots housing each winding phase group corresponds to the number of magnetic poles (twelve) in the rotor
7
.
Air intake openings
1
a
and
2
a
are disposed in axial end surfaces of the front bracket
1
and the rear bracket
2
, and air discharge openings
1
b
and
2
b
are disposed in two outer circumferential shoulder portions of the front bracket
1
and the rear bracket
2
, facing the radial outside of the front-end and rear-end coil ends
52
a
and
52
b
of the stator winding
52
.
Next, the method of constructing the conventional stator
50
will be described with reference to
FIGS. 24
to
27
.
First, belt-shaped bodies having protrusions and recesses are prepared from belt-shaped thin sheets composed of SPCC material being a magnetic material. Then, a parallelepiped laminated core
55
, shown in
FIG. 24
, is prepared by laminating a predetermined number of sheets of the belt-shaped bodies and laser welding an outer portion thereof. Thirtysix slots
55
a
are formed on one side of this laminated core
55
.
A stator winding group
57
A having an overall flat shape is prepared by winding one strand of wire
56
a predetermined number of turns in a wave winding at a pitch of three slots, the strand of wire being composed of an insulated copper wire material having a circular cross section. The winding start and finish ends of the strand of wire
56
constituting this stator winding group
57
A become an output wire
56
a
and a neutral-point
56
b
, respectively. In addition, stator winding groups
57
B and
57
C are similarly prepared by winding a single strand of wire
56
in each case.
Thereafter, the three stator winding groups
57
A,
57
B, and
57
C are superposed so as to be offset by a pitch of one slot and installed in the laminated core
55
by inserting each respective winding group into every third slot
55
a
as shown in FIG.
25
. Thus, the three stator winding groups
57
A,
57
B, and
57
C are installed in the laminated core
55
as shown in FIG.
26
.
Next, the laminated core
55
is bent into a cylindrical shape by means of a shaping device (not shown). Then, the ends of the laminated core
55
are abutted and laser welded to each other to obtain a cylindrical stator core
51
. Thus, a stator is obtained with the three stator winding groups
57
A,
57
B, and
57
C wound into the stator core
51
as shown in FIG.
27
.
In addition, the coil ends of the stator winding groups
57
A,
57
B, and
57
C are molded into the electrically-insulative resin portions
25
to obtain the stator
50
shown in FIG.
23
.
In the stator
50
constructed in this manner, the neutral-points
56
b
of each strand of wire
56
constituting the stator winding groups
57
A,
57
B, and
57
C are connected to obtain the stator winding
52
which is a three-phase alternating-current winding. These stator winding groups
57
A,
57
B, and
57
C have a mutual phase difference of 120° and correspond to an a-phase, b-phase, and c-phase winding group, respectively, of the three-phase alternating-current winding. The output wires
56
a
of each strand of wire
56
constituting the stator winding groups
57
A,
57
B, and
57
C are connected to the rectifier
12
.
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 coil
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
52
, generating electromotive force in the stator winding
52
. This alternating electromotive force passes through the rectifier
12
and is converted into direct current, the magnitude of the voltage is adjusted by the regulator
18
, and the battery is recharged.
At the rear end, external air is drawn in through the air intake openings
2
a
disposed opposite the heat sink of the rectifier
12
and the heat sink
17
of the regulator
18
, respectively, by rotation of the fans
5
, flowing along the axis of the shaft
6
, cooling the rectifier
12
and the regulator
18
, and is then deflected centrifugally by the fans
5
, cooling the rear-end coil end
52
b
of the stator winding
52
before being expelled to the outside through the air discharge openings
2
b
. At the same time, at the front end, external air is drawn in axially through the air intake openings
1
a
by rotation of the fans
5
, and is then deflected centrifugally by the fans
5
, cooling the front-end coil end
52
a
of the stator wi

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