Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-01-10
2001-01-09
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S263000, C310S257000, C310S194000
Reexamination Certificate
active
06172434
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automotive alternator in which electric current is supplied to a rotor coil through lead wires from a slip ring assembly.
2. Description of the Related Art
FIG. 8
is a cross section of a conventional automotive alternator,
FIG. 9
is a perspective of the rotor in
FIG. 8
(part of a fan has been removed), and
FIG. 10
is a partial cross section of FIG.
9
.
This automotive alternator includes: a case
3
consisting of an aluminum front bracket
1
and an aluminum rear bracket
2
; a shaft
6
disposed in the case
3
to one end of which a pulley
4
is secured; a Lundell-type rotor
7
secured to the shaft
6
; fans
5
secured to both ends of the rotor
7
; a stator
8
secured to the inner wall of the case
3
; a slip ring assembly
9
secured to the shaft
6
for supplying electric current to the rotor
7
; a pair of brushes
10
; a brush holder
11
accommodating the brushes
10
; a rectifier
12
in electrical contact with the stator
8
for converting alternating current generated in the stator
8
into direct current; a heat sink
18
fitted over the brush holder
11
; and a regulator
19
fastened to the heat sink
18
with adhesive for adjusting the alternating current generated in the stator
8
.
The rotor
7
includes: a rotor coil
13
composed of wire wound onto a bobbin
14
for generating magnetic flux by passing electric current therethrough; and a pole core
15
disposed so as to cover the rotor coil
13
in which magnetic poles are produced by the magnetic flux generated by the rotor coil
13
. The pole core
15
includes a first pole core body
21
and a second pole core body
22
, each composed of magnetic poles
32
which mutually intermesh, and is prepared by a casting method using mainly low-carbon steel.
The stator
8
includes: a stator core
16
; and a stator coil
17
composed of wire wound into the stator core
16
in which an alternating current is generated by changes in the magnetic flux from the rotor coil
13
as the rotor
7
rotates.
The slip ring assembly
9
includes: slip rings
40
on which the tips of the brushes
10
slide; terminals
41
electrically connected to the slip rings
40
; and a resin portion
42
into which the shaft
6
is pressed, the terminals
41
being embedded by insertion molding into the resin portion
42
except for a portion thereof.
The rectifier
12
includes: an arc-shaped positive-side heat sink
24
having a plurality of fins
24
a
on the reverse side thereof; a plurality of positive-side diodes
23
secured by soldering to a surface of the positive-side heat sink
24
; an arc-shaped negative-side heat sink
26
having a plurality of fins
26
a
on the reverse side thereof; a plurality of negative-side diodes
25
secured by soldering to the negative-side heat sink
26
; and a circuit board
27
for electrically connecting each of the diodes
23
and
25
to the stator coil
17
, the rectifier
12
converting the three-phase alternating current generated by the stator
8
into direct current.
The positive-side heat sink
24
and the negative-side heat sink
26
are composed of aluminum which has high thermal conductivity, and the radially outer negative-side heat sink
26
is grounded by direct attachment to the case
3
. The positive-side diodes
23
and negative-side diodes
25
are formed by molding resin so as to have an overall rectangular shape.
Arc-shaped stays
31
are disposed at even pitch around one of the flanges
30
of the bobbin
14
of the rotor
7
. These stays
31
are engaged in root portions
33
cut into arc shapes between the claw-shaped magnetic poles
32
of the first pole core body
21
to prevent relative displacement between the rotor
7
and the pole core
15
in the circumferential direction. Winding portions
34
having an E-shaped cross section are integrally disposed on a pair of opposing stays
31
. Base end portions
35
b
of lead wires
35
leading from the rotor coil
13
are doubly wound onto these winding portions
34
. These lead wires
35
lie in grooves
36
extending from the root portions
33
to the slip ring assembly
9
. The lead wires
35
are engaged by hooks
37
formed into the resin portion
42
, and the tips
35
a
of the lead wires
35
are doubly wound onto the tips of the terminals
41
. Middle portions of the lead wires
35
are covered by insulation tubing
38
fastened to the grooves
36
with adhesive
44
. This insulation tubing
38
is provided to prevent the corners
43
of the root portions
33
from contacting the lead wires
35
and damaging the enamel coating of the lead wires
35
by abrasion.
In a vehicle alternator of the above construction, a current is supplied from a battery (not shown) through the brushes
10
and slip rings
40
to the rotor coil
13
, whereby magnetic flux is generated, giving rise to a magnetic field, and at the same time the pulley
4
is driven by the engine and the rotor
7
is rotated by the shaft
6
, so that a rotating magnetic field is imparted to the stator coil
17
and electromotive force is generated in the stator coil
17
. This alternating electromotive force passes through the diodes
23
and
25
of the rectifier
12
and is converted into direct current, the magnitude thereof is adjusted by the regulator
19
, and the battery is recharged.
Now, because the pulley ratio between the crank pulley (not shown) of the engine and the pulley
4
of the alternator is normally between 1:2.2 and 1:2.7, the rotor
7
of the automotive alternator is subjected to high operating speeds of 15,000 rpm or more and increases and decreases in rotational load due to sudden acceleration and deceleration of the engine, depending on the rotational frequency of the engine.
Furthermore, during power generation at high speed, the first pole core body
21
and the second pole core body
22
vibrate greatly in the direction of arrow B in
FIG. 13
due to magnetic attraction resulting from power generation arising in the gap A between the stator
8
and the rotor
7
.
When the alternator is generating power, the rotor coil
13
, the stator coil
17
, the positive-side diodes
23
, the negative-side diodes
25
, and the regulator
19
constantly generate heat. For example, in an alternator with a rated output current in the
100
A class, the amount of heat generated is 60 W in the rotor coil 13, 500 W in the stator coil
16
, a total of 120 W in the positive-side diodes
23
and the negative-side diodes
25
, and 6 W in the regulator
19
. The excessive generation of heat by these heat-generating bodies causes deterioration in the performance of the alternator and reduces the working life of the parts.
For that reason, the fans
5
are rotated together with the rotation of the rotor
7
, external air is introduced into the case
3
through openings C in the case
3
by this rotation, and the external air flows as indicated by the arrows D in FIG.
8
. Thus, after cooling the negative-side heat sink
26
, the negative-side diodes
25
, the positive-side heat sink
24
, and the positive-side diodes
23
, the external air is directed radially outwards by the fans
5
, cools the end portions
17
a
of the stator coil
17
in the rear end, and is expelled to the outside through openings E.
External air is also introduced into the case
3
through openings F by the rotation of the fans
5
, and the external air flows as indicated by the arrow G in FIG.
8
. Thus, after cooling the power transistors of the regulator
18
, the external air is directed radially outwards by the fans
5
, cools the end portions
17
a
of the stator coil
17
in the rear end, and is expelled to the outside through openings H.
Similarly, external air introduced through openings I in the front bracket
1
is directed radially outwards by the fans
5
, cooling the end portions
17
b
of the stator coil
17
in the front end. The external air is then expelled outside the case
3
through openings J.
During actual operation of a vehicle, because the ambient temperature wi
Asao Yoshihito
Oohashi Atsushi
Mitsubishi Denki & Kabushiki Kaisha
Perez Guillermo
Ramirez Nestor
Sughrue Mion Zinn Macpeak & Seas, PLLC
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