Alternator

Details Alternator Alternator

2000-10-18

2003-02-25

Lam, Thanh (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S064000, C310S06800R

Reexamination Certificate

active

06525438

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an alternator equipped with a rectifier for rectifying alternating current generated at a stator coil into direct current.
2. Description of the Related Art
FIG. 10
is a sectional view of a conventional automotive alternator,
FIG. 11
is an electrical circuit diagram of the alternator,
FIG. 12
is a front view of a rectifier
12
of
FIG. 10
when the rectifier
12
is observed from inside, and
FIG. 13
is a front view of a rear bracket
2
of FIG.
10
.
The automotive 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
; 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 pair of brushes
10
that slide in contact with the slip ring
9
; a brush holder
11
accommodating the brushes
10
; a rectifier
12
electrically connected to the stator
8
and which rectifies alternating current generated in the stator
8
into direct current; a heat sink
17
fitted in the brush holder
11
; and a regulator
18
adhesively fastened to the heat sink
17
and which adjusts an alternating voltage generated in the stator
8
.
The rotor
7
is equipped with a rotor coil
13
for generating magnetic flux on passage of electric current, and a pole core
14
covering the rotor coil
13
in which magnetic poles are produced by the magnetic flux. The pole core
14
has a pair of a first pole core assembly
21
and a second pole core assembly
22
that intermesh with each other. Centrifugal fans
5
for cooling are welded on axial end surfaces of the first pole core assembly
21
and the second pole core assembly
22
.
The stator
8
is provided with a stator core
15
through which a rotating magnetic field generated by the rotor
7
passes, and a stator coil
16
in which alternating current is generated by the rotating magnetic field. The stator coil
16
is constructed by a first stator coil section
16
a
and a second stator coil section
16
b
, each being formed of three coils whose conductors are wound around the stator core
15
and which are in Y-connection.
FIG. 14
is a front view of the rectifier
12
, and
FIGS. 15 and 16
are exploded front views of the rectifier
12
of FIG.
14
. The rectifier
12
includes positive-side diodes
26
and negative-side diodes
28
connected to output ends of the first stator coil section
16
a
and the second stator coil section
16
b
, and neutral point diodes
30
connected to neutral points
31
of the first stator coil section
16
a
and the second stator coil section
16
b.
The rectifier
12
further includes: a circular strip-shaped positive-side heat sink
24
having, on its surface, six positive-side diodes
26
and two neutral point diodes
30
equidistantly provided on the same circumference; a circular strip-shaped negative-side heat sink
27
disposed radially outside of and on the same plane as the positive-side diodes
26
, and has, on its surface, six negative-side diodes
28
and two neutral point diodes
30
equidistantly provided on the same circumference; and a circuit board
29
electrically connecting the diodes
26
,
28
, and
30
, and the stator coil
16
.
The surfaces of the positive-side heat sink
24
and the negative-side heat sink
27
have recesses
32
and
33
for accommodating the columnar positive-side diodes
26
, the negative-side diodes
28
, and the neutral point diodes
30
.
FIG. 17
shows the positive-side heat sink
24
and the negative-side heat sink
27
of the FIG.
15
as observed from a rear side. On the rear surfaces of the heat sinks
24
and
27
, protuberances
34
and
35
are formed at the same time when the recesses
32
and
33
are formed.
The positive-side diodes
26
, the negative-side diodes
28
, and the neutral point diodes
30
are fixed to the recesses
32
and
33
of the heat sinks
24
and
27
by soldering. Perpendicularly extending lead wires
36
and
37
of the diodes
26
,
28
, and
30
are electrically connected to terminals
38
and
39
of the circuit board
29
.
The positve-side heat sink
24
is retained on the negative-side heat sink
27
via a holder
40
. The positive-side heat sink
24
, the negative-side heat sink
27
, and the circuit board
29
are fixed in the case
3
by screws (not shown) attached to the rear bracket
2
via through holes
41
. Furthermore, the negative-side heat sink
27
is grounded by being directly attached to the rear bracket
2
.
In the automotive alternator having the construction set forth above, electric current is supplied from a battery (not shown) to the rotor coil
13
via the brushes
10
and the slip ring
9
, generating magnetic flux. The pulley
4
is driven by an engine, and the rotor
7
is rotated by the shaft
6
. This causes a rotating magnetic field to be imparted to the stator coil
16
, so that an electromotive force is generated in the stator coil
16
. The alternating electromotive force is converted into direct current through the positive-side diodes
26
and the negative-side diodes
28
of the rectifier
12
, a magnitude thereof is adjusted by the regulator
18
, and the battery is recharged.
The rotor coil
13
, the stator coil
16
, the positive-side diodes
26
, the negative-side diodes
28
, and the regulator
18
constantly generate heat during power generation. When an alternator of, for example, a 100A rated output current class, runs at a speed generating a high temperature, the rotor coil
13
generates a calorific value of 60W, the stator coil
16
generates a caloric value of 500W, the positive-side diodes
26
and the negative-side diodes
28
together generate a calorific value of 120W, and the regulator
18
generates a calorific value of 6W. Excessive heat generation causes deteriorated performance of the alternator and shortens lives of components.
As countermeasures for the heat generation, the fans
5
rotate as the rotor
7
rotates. The rotation of the fans
5
causes outside air to be introduced into the case
3
through an aperture A of the case
3
, and to flow as indicated by arrows a of
FIG. 10
to thereby cool the negative-side heat sink
26
, the negative-side diodes
28
, the positive-side heat sink
24
, and the positive-side diodes
26
. The outside air is then led radially outward by the fans
5
to cool a coil end of the stator coil
16
at the rear side, and exhausted to open air through an aperture B.
Furthermore, the rotation of the fans
5
causes outside air to be introduced into the case
3
also through an aperture C. The outside air flows as indicated by arrows &bgr; of
FIG. 10
to cool a power transistor of the regulator
18
. The outside air is then led radially outward by the fans
5
to cool a coil end of the stator coil
16
at the rear side, and exhausted to open air through an aperture D.
Similarly, outside air introduced through apertures E of the front bracket
1
is directed radially outward by the fans
5
to cool an end of the stator coil
16
at a front side. The outside air is then exhausted out of the case
3
through an aperture F.
In the automotive alternator having the construction described above, the lead wires
36
and
37
of the positive-side diodes
26
and the negative-side diodes
28
, which extend in an axial direction of the shaft
6
, are directly abutted against the terminals
38
and
39
of the circuit board
29
. For this reason, the six positive-side diodes
26
and the two neutral point diodes
30
are disposed at equal intervals on the circumference of the positive-side heat sink
24
, and the six negative-side diodes
28
and the two neutral point diodes
30
are disposed at equal intervals on the circumference of the negative-side heat sink
27
. Therefore, the positive-side diodes
26
, in particular, on the positive-side heat s

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