Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-01-26
2004-03-02
Tamai, Karl (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S058000
Reexamination Certificate
active
06700239
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automotive alternator provided with a blowing means.
The entire content of the basic Japanese Patent Application from which the priority under the Convention is claimed in this application is hereby incorporated by reference into this application.
2. Description of the Related Art
FIG. 25
is a cross section of a conventional automotive alternator, and
FIGS. 26 and 27
are front elevations showing a front-end fan and a rear-end fan, respectively, used in a rotor of the conventional automotive alternator.
This 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
8
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
such 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
8
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
8
and converts alternating current generated in the stator
8
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 Lundell-type front-end and rear-end pole cores
20
and
21
disposed so as to cover the rotor coil
13
, magnetic poles being formed in the front-end and rear-end pole cores
20
and
21
by magnetic flux generated in the rotor coil
13
. The pair of front-end and rear-end pole cores
20
and
21
are made of iron, each has a number of front-end and rear-end 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 front-end and rear-end pole cores
20
and
21
are fastened to the shaft
6
facing each other such that the front-end and rear-end claw-shaped magnetic poles
22
and
23
intermesh.
The front-end and rear-end fans
5
A and
5
B are each prepared by form-working a metal plate, and each includes an annular fan base portion
5
a
, a number of blade base plates
5
b
extending radially outwards from outer peripheral portions of the fan base portions
5
a
, and blades
5
c
formed by folding and bending an outer peripheral portion of each of the blade base plates
5
b
. The front-end and rear-end fans
5
A and
5
B are fastened to front and rear axial ends of the front-end and rear-end pole cores
20
and
21
, respectively.
The stator
8
is constituted by a stator core
15
, and a stator coil
16
formed by winding a conducting wire into this stator core
15
, alternating current being generated in the stator coil
16
by changes in magnetic flux from the rotor
7
accompanying rotation of the rotor
7
. Portions of the stator coil
16
extend from front and rear axial ends of the stator core
15
and constitute a front-end coil end group
16
f
and a rear-end coil end group
16
r.
In automotive alternators 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 front-end claw-shaped magnetic poles
22
in the front-end pole core
20
are magnetized with north-seeking (N) poles by this magnetic flux, and the rear-end claw-shaped magnetic poles
23
in the rear-end 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 coil
16
, generating electromotive force in the stator coil
16
. This alternating electromotive force passes through the rectifier
12
and is rectified into direct current, the output thereof is adjusted by the regulator
18
, and the battery is recharged.
In this automotive alternator, the rotor coil
13
, the stator coil
16
, the rectifier
12
, and the regulator
18
continuously generate heat during power generation, and in an alternator having a rated output current in the 100A class, these components generate 60W, 500W, 120W, and 6W of heat energy, respectively, at rotational frequencies at which the temperature is high.
Thus, in order to cool the heat generated by power generation, front-end and rear-end air intake apertures
1
a
and
2
a
and front-end and rear-end air discharge apertures
1
b
and
2
b
are disposed in the front bracket
1
and the rear bracket
2
. More specifically, as shown in
FIG. 25
, a number of the front-end and rear-end air intake apertures
1
a
and
2
a
are disposed in lines circumferentially in axial surfaces (end surfaces) of the front bracket
1
and the rear bracket
2
, respectively, and a number of the front-end and rear-end air discharge apertures
1
b
and
2
b
are disposed in lines circumferentially in radial surfaces (side surfaces) of the front bracket
1
and the rear bracket
2
, respectively.
At the rear end, as indicated by arrows in
FIG. 25
, external air is sucked into the case
3
through the rear-end air intake apertures
2
a
by rotation of the rear-end fans
5
B, cooling the rectifier
12
and the regulator
18
, and is then deflected centrifugally by the rear-end fans
5
B, cooling the rear-end coil end group
16
r
of the stator coil
16
before being expelled to the outside through the rear-end air discharge apertures
2
b
. At the same time, at the front end, as indicated by arrows in
FIG. 25
, external air is sucked into the case
3
through the front-end air intake apertures
1
a
by rotation of the front-end fans
5
A and is then deflected centrifugally by the front-end fans
5
A, cooling the front-end coil end group
16
f
of the stator coil
16
before being expelled to the outside through the front-end air discharge apertures
1
b
. In addition, a cooling air flow flows from the front end to the rear end as a result of a pressure difference between the front end and the rear end, cooling the rotor coil
13
.
When the conventional automotive alternator constructed in this manner is operated at a rotational frequency of 5000 rpm, the air flow rate in each of the ventilation pathways has been such that the front-end intake air flow rate Qf
IN
was 0.025 m
3
/s, the front-end discharge air flow rate Qf
OUT
was 0.02 m
3
/s, the rear-end intake air flow rate Qr
IN
was 0.03 m
3
/s, the rear-end discharge air flow rate Qr
OUT
was 0.035 m
3
/s, and the front-to-rear air flow rate Q
f→r
was 0.005 m
3
/s.
This conventional automotive alternator is constructed such that the rear-end flow rates are greater than the front-end flow rates. Thus, at the rear end, because the large volume of cooling air taken in through the rear-end air intake apertures
2
a
is warmed as it cools the rectifier
12
and the regulator
18
and is then supplied for the cooling of the rear-end coil end group
16
r
of the stator coil
16
, temperature increases in the rear-end coil end group
16
r
cannot be sufficiently suppressed. Similarly, at the front end, because the small volume of cooling air taken in through the front-end air intake apertures
1
a
is supplied for the cooling of the front-end coil end group
16
f
of the stator coil
16
, temperature increases in the front-end coil end group
16
f
cannot be sufficiently suppressed. In other words
Adachi Katsumi
Asao Yoshihito
Mitsubishi Denki & Kabushiki Kaisha
Tamai Karl
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