Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-12-18
2002-09-10
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S06000A, C310S061000
Reexamination Certificate
active
06448687
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vehicle-mounted automotive alternator, and more particularly, to the number of blades of fans mounted on a rotor.
2. Description of the Related Art
FIG. 24
is a sectional view showing a construction of an ordinary automotive alternator.
FIG. 25
is a perspective view of a rotor shown in FIG.
24
.
The automotive alternator is arranged such that a Lundell-type rotor
7
is rotatably mounted in a case
3
composed of an aluminum front bracket
1
and an aluminum rear bracket
2
through a shaft
6
, and a stator
8
is fastened to the inner wall surface of the case
3
so as to cover the inner 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 fastened to an end of the shaft
6
so as to transmit the rotational torque of an engine to the shaft
6
through a belt (not shown).
Slip rings
9
are fastened to the other end of the shaft
6
to supply current to the rotor
7
and a pair of brushes
10
are accommodated in a brush holder
11
disposed in the case
3
so as to be in sliding contact with the slip rings
9
. A regulator
18
is adhered to a heat sink
17
fitted to the brush holder
11
to regulate the magnitude of AC voltage generated by the stator
8
. Rectifiers
12
, which are electrically connected to the stator
8
, are mounted in the case
3
to rectify alternate current generated by the stator
8
to direct current.
The rotor
7
includes 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 poles cores
20
and
21
are made of iron and have cylindrical core base portions
22
a
and
23
a
and a plurality of claw-shaped magnetic poles
22
and
23
disposed radially externally on the outer circumferential perimeters of the core base portions
22
a
and
23
a
at even pitch, respectively, the end surfaces of the core base portions
22
a
and
23
a
are abutted against each other, 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.
Fans
5
, each having a plurality of blades
5
c
in the vicinity of the outer circumference thereof, are mounted on the end surfaces of the cylindrical core base portions
22
a
and
23
a
at both the ends of the rotor
7
to be driven in the axial direction thereof. Each fan
5
has a thin base sheet
5
a
and the plurality of blades
5
c
formed by cutting and raising the base sheet
5
a.
The stator
8
includes a stator core
15
, and a stator coil
16
from which alternate current is generated by the change of magnetic flux from the rotor
7
as the rotor
7
rotates, the stator coil
16
being composed of a conductive wire wound around the stator core
15
.
In the automotive alternator constructed in this manner, current is supplied from a battery (not shown) to the rotor coil
13
by means of the brushes
10
and the slip rings
9
, and the magnetic flux is generated. The claw-shaped magnetic poles of one pole core
20
are magnetized to N polarities by the magnetic flux, and the claw-shaped magnetic poles
23
of the other pole core
21
are magnetized to S polarities. On the other hand, 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 direct current by means of the rectifiers
12
, its voltage is regulated by the regulator
18
, and the battery is recharged.
In the automotive alternator, the rotor coil
13
, the stator coil
16
, the rectifiers
12
, and the regulator
18
generate heat at all time while power is generated. To cool heat generated by the power generation, air intake vents
1
a
and
2
a
and air discharge vents l
b
and
2
b
are disposed in the front bracket
1
and the rear bracket
2
.
As shown by an arrow in
FIG. 24
, at a rear-end, external air is sucked into the case
3
through the air intake vents
2
a
by means of the rotation of a fan
5
and cools the rectifiers
12
and the regulator
18
, then cools the rear-end coil end of the stator coil
16
by being deflected centrifugally by the fan
5
, and thereafter is discharged to the outside from the air discharge vents
2
b.
As shown by an arrow in
FIG. 24
, at a front-end, external air is sucked into the case
3
through the air intake vents
1
a
by the rotation of a fan
5
, cools the front-end coil end of the stator coil
16
by being deflected centrifugally by the fan
5
, and thereafter is discharged to the outside from the air discharge vents
1
b.
Further, cooling wind generated by a pressure difference between the front-end and the rear-end flows from the front-end to the rear-end through the inside of the rotor
7
, and cools the rotor coil
13
.
In general, automotive alternators, which are auxiliary machines mounted on vehicles, are required to have a performance to cope with the requirement for reducing noise outside vehicle and for making compartment quiet. The alternator includes a rotating member rotating at the large number of rotation at all times, which causes a problem of wind noise and magnetic noise. Further, the alternator, which is a heating member, is increasingly put in thermally hostile environments by the reduction of a space in which equipment are mounted. When, for example, the capacity of the fans
5
as a cooling means is increased to cope with the above problem, noise caused by the fans
5
may be increased. Further, when the cooling property of the alternator is reduced, an output of the alternator is decreased.
As a method of solving the above problem, Japanese Unexamined Patent Application Publication No. 11-220851 discloses to prevent an increase in noise by making the number of blades of fans
5
smaller than the number of claw-shaped magnetic poles. That is, the method prevents noise caused by the vibration of the claw-shaped magnetic poles when they rotate from being synchronized with noise caused by fan blades
5
c.
Incidentally, there is provided the even number of claw-shaped magnetic poles to alternately form N-poles and S-poles. Therefore, when the even number of fan blades
5
c
is used at any one of a front-end and a rear-end, they include the number of resonance which is resonated with the number of the claw-shaped magnetic poles. Particularly, in an automotive alternator whose frequency of rotation has a considerably wide range, it is a problem that the above method does not act as a perfect countermeasure for suppressing interference noise.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention, which was made to solve the above problems, to provide a small automotive alternator having a high output and excellent in a cost performance without reducing the cooling property thereof even at high environmental temperature.
In an automotive alternator according to the present invention including a case having a plurality of air intake vents disposed in the axial surface thereof and a plurality of air discharge vents disposed in the radial surface thereof, a rotor having a pair of pole cores including claw-shaped magnetic poles projecting radially externally from the outer circumferential perimeters thereof at even pitch, respectively, fastened to a shaft such that the claw-shaped magnetic poles intermesh and rotatably disposed in the case, the pair of pole cores having a pair of fans, which include a plurality of blades around the outer circumferences thereof, and being fastened to the axial end surfaces thereof; and a stator fastened to the case so as to cover the outer circumference of the rotor, and having a stator c
Asao Yoshihito
Higashino Kyoko
Mitsubishi Denki & Kabushiki Kaisha
Nguyen Tran
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