Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-01-06
2001-03-27
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S108000, C310S071000
Reexamination Certificate
active
06208058
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automotive alternator, and in particular, relates to the construction of a stator coil of an automotive alternator for suppressing damage to the insulation coated on the coil wire by eliminating three-dimensional twisting of the coil wire and for improving productivity.
2. Description of the Related Art
FIG. 11
is a cross-section showing a conventional automotive alternator.
A conventional automotive alternator includes: a Lundell-type rotor
7
mounted so as to rotate freely by means of a shaft
6
within a case
3
consisting of an aluminum front bracket
1
and an aluminum rear bracket
2
; and a stator
8
secured to the inner wall of the case
3
so as to cover the outer circumference of the rotor
7
.
The shaft
6
is rotatably supported by the front bracket
1
and the rear bracket
2
. A pulley
4
is secured to one end of the shaft
6
to enable rotational torque from an engine to 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 secured to the other end of the shaft
6
, and a pair of brushes
10
are housed in a brush holder
11
disposed within the case
3
so as to slide in contact with the slip rings
9
. A regulator
18
for regulating the magnitude of an alternating voltage generated in the stator
8
is affixed by adhesive to a heat sink
17
attached to the brush holder
11
. A rectifier
12
electrically connected to the stator
8
for rectifying an alternating current generated in the stator
8
to a direct current is mounted within the case
3
. This rectifier
12
is provided with a plurality of diodes
24
arranged on a heat sink
19
, and a circuit board
25
for electrically connecting each of the diodes
24
and forming predetermined circuits.
The rotor
7
includes: a rotor coil
13
for generating magnetic flux by passing electric current therethrough; and a pair of pole cores
20
and
21
disposed so as to cover the rotor coil
13
in which magnetic poles are formed by the magnetic flux generated by the rotor coil
13
. The pair of pole cores
20
and
21
are made of iron, each has a plurality of claw-shaped magnetic poles
22
and
23
projecting from an outer circumferential edge thereof spaced at even angular pitch circumferentially, and the pole cores
20
and
21
are secured to the shaft
6
facing each other so that the claw-shaped magnetic poles
22
and
23
intermesh. In addition, fans
5
are secured to both axial ends of the rotor
7
.
The stator
8
includes: a stator core
15
; and a stator coil
16
composed of wire wound around the stator core
15
in which an alternating current is generated by changes in the magnetic flux from the rotor
7
as the rotor
7
rotates.
In an automotive alternator constructed in this manner, an electric current is supplied from a battery (not shown) by means of the brushes
10
and the slip rings
9
to the rotor coil
13
, and the magnetic flux is generated. The claw-shaped magnetic poles
22
of the pole core
20
, are magnetized to N polarities by the magnetic flux, and the claw-shaped magnetic poles
23
of the pole core
21
are magnetized to S polarities by the magnetic flux. At the same time, the rotational torque of the engine is transmitted to the shaft
6
by means of the belt and the pulley
4
, and the rotor
7
is rotated. Thus, a rotating magnetic field is imparted to the stator coil
16
and electromotive force is generated in the stator coil
16
. This alternating electromotive force is rectified to a direct current by means of the rectifier
12
, its voltage is regulated by the regulator
18
, and the battery is recharged.
Next, the stator coil construction applied to a conventional automotive alternator will be explained with reference to FIG.
12
. Moreover,
FIG. 12
is a partial enlargement of a conventional stator viewed from the inner circumferential side.
The stator core
15
is formed into a cylindrical shape and a plurality of slots
15
a
whose grooves extend in the axial direction are disposed at even angular pitch around the circumference thereof so as to be open on the inner circumferential side. The stator coil
16
is constructed by connecting into one unit the starting end wires (or the finishing end wires) of three coils respectively corresponding to three phases prepared by inserting wire in a wave shape successively into every third slot
15
a
. Moreover, the slots
15
a
into which the strands of wire of each of the three coils are inserted are offset from those of each of the other coils by one slot. Further, the wire extends axially outwards from the slots
15
a
and constitutes front-end and rear-end coil end portions
16
a
and
16
b.
Next, the construction of the stator coil
16
will be explained in detail.
Coil segments
30
are formed by shaping strands of copper wire coated with insulation into a general U-shape, and as shown in
FIGS. 13 and 14
, each includes a pair of straight portions
30
a
, a pair of oblique portions
30
b
each bent from a straight portion
30
a
and extending in a straight line, and a return portion
30
c
joining the pair of oblique portions
30
b
by twisting and bending the wire so as to turn back around.
Now, the coil segments
30
are inserted from the rear end into pairs of slots
15
a
three slots apart. At this time, the coil segments
30
are inserted into the slots
15
a
such that the strands of wire are folded back at the return portions
30
c
, from the inner circumferential side to the outer circumferential side, for example. Then, the straight portions
30
a
of the coil segments
30
projecting towards the front end from the slots
15
a
are bent circumferentially outwards, as shown in
FIG. 15
, and the ends thereof are additionally bent parallel to the straight portions
30
a
. Next, adjacent ends of the coil segments
30
are joined to prepare one phase of the coil. At this time, the adjacent ends of the coil segments
30
are stacked radially and joined, and constructed such that the strands of wire appear to be folded back from the inner circumferential side to the outer circumferential side at the joined portions.
The other two phases of the coil are prepared similarly. For each of the phases of the coil, the slots
15
a
into which the coil segments
30
are inserted are offset by one slot from each of the other phases.
The stator coil
16
is constructed by connecting the three phases of coil prepared in this manner in a three-phase alternating-current connection such as a Y connection or a delta connection.
In the coil end portions
16
a
and
16
b
of a stator coil
16
constructed in this manner, because the wire is formed so as to bend back from the inner circumferential side to the outer circumferential side at the apex, adjacent strands of wire are neatly arranged in the circumferential direction in the vicinity of the apexes, as shown in
FIGS. 17 and 18
. Moreover,
FIG. 17
is a diagram showing an example of a wire array in a rear-end coil end portion, and
FIG. 18
is a diagram showing another example of a wire array in a rear-end coil end portion. By adopting constructions of this kind, the coil end portions become practically the same shape around the entire circumference, improving alignment.
Moreover, in the above conventional example, all of the straight portions
30
a
projecting towards the front end from the slots
15
a
were bent circumferentially outwards, but some of the straight portions
30
a
projecting towards the front end from the slots
15
a
may be bent circumferentially inwards and the tips thereof additionally bent parallel to the straight portions
30
a
, as shown in FIG.
16
.
A conventional stator coil
16
applied to an automotive alternator is constructed by inserting the straight portions
30
a
of many generally U-shaped coil segments
30
into predetermined slots
15
a
, bending the straight portions
30
a
projecting from the slots
15
a
circumferentially in the vicinity of the end surface of th
Asao Yoshihito
Higashino Kyoko
Taji Ryoichi
Mitsubishi Denki & Kabushiki Kaisha
Nguyen Tran
Sughrue Mion Zinn Macpeak & Seas, PLLC
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