Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-06-02
2001-12-25
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S156660
Reexamination Certificate
active
06333582
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an alternator driven by an internal combustion engine, and more particularly, to a rotor for the alternator mounted to a vehicle such as a passenger car and a truck.
2. Description of the Related Art
FIG. 12
is a cross-sectional view showing a conventional alternator for a vehicle.
FIG. 13
is a perspective view showing a rotor for the conventional alternator for a vehicle.
In
FIGS. 12 and 13
, the alternator for a vehicle is constructed such that a Lundell-type rotor
7
is rotatably mounted within a casing
3
including an aluminum front bracket
1
and an aluminum rear bracket
2
by means of a shaft
6
, and a stator
8
is fixedly attached to an inner wall surface of the casing
3
so as to cover an outer circumferential side of the rotor
7
. Fans
5
are fixedly attached to both ends of the rotor
7
in its axial direction.
The shaft
6
is rotatably supported by the front bracket
1
and the rear bracket
2
. A pulley
4
is fixedly attached to one end of the shaft
6
to enable rotational torque from an engine to 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 fixedly attached to the other end portion of the shaft
6
. A pair of brushes
10
are housed in a brush holder
11
disposed within the casing
3
so as to slide in contact with the slip rings
9
. A regulator
18
for regulating the magnitude of an alternating voltage caused by the stator
8
is adhered to a heat sink
17
fitted to the brush holder
11
. Further, a rectifier
12
electrically connected to the stator
8
and rectifying an alternating current caused by the stator
8
to a direct current is mounted into the casing
3
.
The rotor
7
has a field winding
13
which generates magnetic flux when an electric current flows therein, and a pair of rotor iron cores
20
and
21
disposed so as to cover the field winding
13
in which magnetic poles are formed by the magnetic flux generated by the field winding
13
. The rotor iron cores
20
and
21
are made of iron and each has disk-shaped basic portions
22
a
and
23
a
and plural claw-shaped magnetic poles
22
b
and
23
b
projecting from outer circumferential edges of the basic portions
22
a
and
23
a
at an equiangular pitch circumferentially. Central holes are bored in the basic portions
22
a
and
23
a
. Each of the claw-shaped magnetic poles
22
b
and
23
b
is approximately formed in a trapezoidal shape projecting in a tapered shape in an axial direction. The pair of rotor iron cores
20
and
21
are fitted to the shaft
6
and are integrated with the shaft
6
by abutting end surfaces of the basic portions
22
a
and
23
a
so as to engage the claw-shaped magnetic poles
22
b
and
23
b
with each other. Further, permanent magnets
19
are fixedly attached between the claw-shaped magnetic poles
22
b
and
23
b
adjacent to each other , respectively, and are magnetized in a direction in which leakage of the magnetic flux between these claw-shaped magnetic poles
22
b
and
23
b
is reduced.
The stator
8
has a stator iron core
15
and a stator winding
16
constructed by winding a lead wire around the stator iron core
15
in which the alternating current is generated by alternating the magnetic flux from the field winding
13
owing to the rotation of the rotor
7
.
In the alternator for a vehicle having such a construction, an electric current is supplied from a battery (not shown) to the rotor coil
13
by means of the brushes
10
and the slip rings
9
so that the magnetic flux is generated. The claw-shaped magnetic poles
22
b
of one field core
20
are magnetized to N-polarities by the magnetic flux and the claw-shaped magnetic poles
23
b
of the other field core
21
are magnetized to S-polarities.
In contrast to this, the rotational torque from the engine is transmitted to the shaft
6
by means of the belt and the pulley
4
so that the rotor
7
is rotated. Therefore, a rotating magnetic field is imparted to the stator winding
16
and the electromotive force is generated in the stator winding
16
. This alternating electromotive force is rectified to a direct current by means of the rectifier
12
, and the regulator
18
regulates its magnitude and the direct current is charged to the battery.
Most of magnetic flux generated by the field winding
13
enter the stator
8
from the claw-shaped magnetic poles
22
b
of the field core
20
magnetized to the N-polarities, and then enter the interior of the field core
21
from the claw-shaped magnetic poles
23
b
of the field core
21
magnetized to the S-polarities through the interior of the stator
8
, and again enter the stator
8
from the claw-shaped magnetic poles
22
b
of the field core
20
. Thus, the above magnetic flux constitutes a closing circuit. At this time, magnetic flux leaked from a portion between the claw-shaped magnetic poles
22
b
and
23
b
are reduced by the permanent magnets
19
. Thus, invalid magnetic flux not contributing to power generation is reduced and power generation efficiency of the alternator is increased.
Since the rotor
8
of this conventional alternator for a vehicle is constructed as mentioned above, the magnetic attractive force is applied to the claw-shaped magnetic poles
22
b
and
23
b
by the magnetic flux in gaps between the claw-shaped magnetic poles
22
b
and
23
b
and the stator
8
during an operation of the alternator for a vehicle. This magnetic flux is continuously changed with the passage of time, and the magnetic attractive force is applied to the claw-shaped magnetic poles
22
b
and
23
b
as swinging force. Thus, as shown by an arrow in
FIG. 14
, a problem exists in that the claw-shaped magnetic poles
22
b
and
23
b
are swung, i.e., resonated so that uncomfortable noises (electromagnetic noises) are caused and heard.
Further, the claw-shaped magnetic poles
22
b
and
23
b
are vibrated by the magnetic attractive force with large amplitude as it approaches tip sides of the claw-shaped magnetic poles
22
b
and
23
b
. The claw-shaped magnetic poles
22
b
and
23
b
are mutually vibrated in reverse phases. In the conventional rotor
8
, the permanent magnets
19
are fixedly attached to the claw-shaped magnetic poles
22
b
and
23
b
and are constructed as an integral body. Accordingly, a problem also exists in that there is a fear that the permanent magnets
19
fixedly attached to the claw-shaped magnetic poles
22
b
and
23
b
are distorted and damaged by such vibration of the claw-shaped magnetic poles
22
b
and
23
b.
For example, improving measures for preventing such damage of the permanent magnets are proposed in Japanese Patent Application Laid-Open No. Hei 11-136913. In these improving measures, each permanent magnet interposed between the claw-shaped magnetic poles adjacent to each other is divided into two permanent magnet pieces, and the divided permanent magnet pieces are respectively directly fixedly attached to the adjacent claw-shaped magnetic poles, or are respectively fixedly attached to the adjacent claw-shaped magnetic poles by using supporting members.
However, in such improving measures, strength of the magnet is secured, but these improving measures are not positively taken to reduce the resonance of each of the claw-shaped magnetic poles. Accordingly, no improving measures contribute to a reduction in displacement of each of the claw-shaped magnetic poles so that no uncomfortable noises can be reduced. Further, when the permanent magnet pieces are fixedly attached to the claw-shaped magnetic poles by using the supporting members, the supporting members, the permanent magnet pieces and the claw-shaped magnetic poles are integrated with each other so that only volume is simply increased. Therefore, the vibration of the claw-shaped magnetic poles is ununiformly dispersed by rotation so that there is also a fear that the rasping noises become bigger. Further, the alternator is set to a state in which weight is
Adachi Katsumi
Asao Yoshihito
Higashino Kyoko
Tsuruhara Kenji
Mitsubishi Denki & Kabushiki Kaisha
Nguyen Tran
Sughrue & Mion, PLLC
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