Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-09-26
2003-09-09
Le, Dang (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S063000
Reexamination Certificate
active
06617718
ABSTRACT:
This application is based on Application No. 2000-007925, filed in Japan on Jan. 16, 2001, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automotive alternator and particularly to a positional relationship between a cooling fan and a stator winding.
2. Description of the Related Art
FIG. 10
is a cross section showing a conventional automotive alternator.
In
FIG. 10
, the automotive alternator includes: a case
3
constituted by an aluminum front bracket
1
and an aluminum rear bracket
2
; a shaft
6
disposed inside the case
3
having a pulley
4
secured to a first end thereof; a Lundell-type rotor
7
secured to the shaft
6
; front-end and rear-end centrifugal fans
5
functioning as cooling fans secured to front and rear axial end surfaces of the rotor
7
; a stator
8
secured to the case
3
so as to envelop the rotor
7
; slip rings
9
secured to a second end of the shaft
6
for supplying electric current to the rotor
7
; a pair of brushes
10
sliding on surfaces of the slip rings
9
; a brush holder
11
accommodating the brushes
10
; a rectifier
12
electrically connected to the stator
8
for converting alternating current generated in the stator
8
into direct current; and a regulator
18
mounted to a regulator heat sink
17
fitted onto the brush holder
11
, the regulator
18
adjusting the magnitude of an alternating voltage generated in the stator
8
.
The rotor
7
is constituted by a field winding
13
for generating a magnetic flux on passage of an electric current, and a pair of first and second pole cores
20
and
21
disposed so as to cover the field winding
13
, magnetic poles being formed in the first and second pole cores
20
and
21
by magnetic flux generated in the field winding
13
. The pair of first and second pole cores
20
and
21
are made of iron, each has a plurality of first and second claw-shaped magnetic poles
22
and
23
having a generally trapezoidal outermost diameter surface shape disposed on an outer circumferential edge portion at even angular pitch in a circumferential direction so as to project axially, and the first and second pole cores
20
and
21
are fixed to the shaft
6
facing each other such that the first and second claw-shaped magnetic poles
22
and
23
intermesh.
The stator
8
is constituted by: a cylindrical stator core
15
formed by laminating a magnetic steel plate; and a stator winding
16
installed in the stator core
15
. The stator
8
is held between the front bracket
1
and the rear bracket
2
so as to form a uniform air gap between outer circumferential surfaces of the claw-shaped magnetic poles
22
and
23
and an inner circumferential surface of the stator core
15
.
The rectifier
12
is constituted by: unidirectional conducting component packages
24
for three-phase full-wave rectification of output from the stator winding
16
; a pair of rectifier heat sinks
25
; and a circuit board
26
in which wiring constituting a bridge circuit is insert molded. The unidirectional conducting component packages
24
are each formed into a generally rectangular parallelepiped shape by molding a diode
24
a
joined to a heat-dissipating tab
24
b
into an electrically-insulating resin portion
24
c.
A predetermined number of the unidirectional conducting component packages
24
are mounted to each of the rectifier heat sinks
25
by joining the heat-dissipating tabs
24
b
to a main surface of each of the rectifier heat sinks
25
.
In an automotive alternator constructed in this manner, an electric current is supplied from a battery (not shown) through the brushes
10
and the slip rings
9
to the field winding
13
, generating a magnetic flux. The first claw-shaped magnetic poles
22
on the first pole core
20
are magnetized into North-seeking (N) poles by this magnetic flux, and the second claw-shaped magnetic poles
23
on the second pole core
21
are magnetized into South-seeking (S) poles.
At the same time, the pulley
4
is driven by an engine and the rotor
7
is rotated by the shaft
6
. A rotating magnetic field is applied to the stator core
15
due to the rotation of the rotor
7
, generating an electromotive force in the stator winding
16
. The alternating electromotive force generated in the stator winding
16
is converted into direct current by the rectifier
12
and the magnitude of the voltage output therefrom is adjusted by the regulator
18
, recharging the battery.
Now, the field winding
13
, the stator winding
16
, the rectifier
12
, and the regulator
18
continuously generate heat during power generation, and in an automotive alternator having a rated output current in the
100
A class, the amount of heat generated at rotational frequencies at which the temperature is high is 60W, 500W, 120W, and 6W, respectively.
Thus, in order to cool the heat generated by power generation, front-end and rear-end air intake apertures
1
a
and
2
a
are disposed through axial end surfaces of the front bracket
1
and the rear bracket
2
, and front-end and rear-end air discharge apertures
1
b
and
2
b
are disposed through radial side surfaces of the front bracket
1
and the rear bracket
2
so as to face coil end groups
16
f
and
16
r
of the stator winding
16
.
Thus, the centrifugal fans
5
are rotated and driven together with the rotation of the rotor
7
, and front-end and rear-end cooling airflow channels are formed in which external air is sucked inside the case
3
through the front-end and rear-end air intake apertures
1
a
and
2
a,
flows axially towards the rotor
7
, is then deflected centrifugally by the centrifugal fans
5
, thereafter crosses the coil end groups
16
f
and
16
r,
and is discharged outside through the front-end and rear-end air discharge apertures
1
b
and
2
b.
A rotor cooling airflow channel is also formed in which a cooling airflow flows through the inside of the rotor
7
from a front end to a rear end as a result of a pressure difference between the front end and the rear end of the rotor
7
.
As a result, heat generated in the stator winding
16
is dissipated from the coil end groups
16
f
and
16
r
to the front-end and rear-end cooling airflows, suppressing temperature increases in the stator
8
. Furthermore, heat generated in the diodes
24
a
and the regulator
18
is dissipated to the rear-end cooling airflow through the rectifier heat sinks
25
and the regulator heat sink
17
, suppressing temperature increases in the rectifier
12
and the regulator
18
. In addition, heat generated in the field winding
13
is dissipated to the rotor cooling airflow flowing through the rotor
7
, thereby suppressing temperature increases in the rotor
7
.
In the automotive alternator constructed in this manner, heat-generating parts such as the stator
8
, the rectifier
12
, etc., are cooled by the cooling airflows flowing through the cooling airflow channels formed by the centrifugal fans
5
.
Here, inflow flow rates of the cooling airflows flowing through the cooling airflow channels depend on ventilation resistance in the cooling airflow channels, the inflow flow rates decreasing as ventilation resistance increases. This decrease in the inflow flow rates of the cooling airflows causes a decrease in cooling of the rectifier
12
and the regulator
18
. Furthermore, an amount of overlap between the front-end centrifugal fan
5
and the front-end coil end group
16
f
and between the rear-end centrifugal fan
5
and the rear-end coil end group
16
r
(an axial length of radial overlap between the two in each case) is one of the factors increasing ventilation resistance in the cooling airflow channels. In other words, if the amount of overlap increases, ventilation resistance increases. Cooling of the stator winding
16
is raised as the amount of overlap increases.
Thus, increasing the amount of overlap between the front-end centrifugal fan
5
and the front-end coil end group
16
f
and between the rear-end centrifugal fan
5
Asao Yoshihito
Oohashi Atsushi
Le Dang
Mitsubishi Denki & Kabushiki Kaisha
Sughrue & Mion, PLLC
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