Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-08-08
2002-06-11
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S049540, C310S261100
Reexamination Certificate
active
06404096
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an alternating current generator for vehicle having a rotor of claw pole type.
FIGS. 13
to
17
show a configuration of a conventional alternating current generator for vehicle.
FIG. 13
is a sectional view of the generator, and
FIG. 14
is a perspective view of a rotor, and
FIG. 15
is a perspective view of a stator, and
FIG. 16
is a perspective view of a stator core, and
FIG. 17
is a plane view showing a shape of magnetic poles of the rotor. In the drawings, numeral
1
is a front bracket, and numeral
2
is a rear bracket, and numeral
3
is a stator sandwiched between the front bracket
1
and the rear bracket
2
. The stator
3
comprises a stator core
4
and a three-phase stator coil
5
inserted into a slot
4
a
of the stator core
4
as shown in
FIGS. 13
,
15
and
16
.
In
FIGS. 13 and 14
, numeral
6
is a rotor of claw pole type. The rotor
6
comprises a rotating shaft
7
whose both ends are supported by the front bracket
1
and the rear bracket
2
, a first rotor core
8
and a second rotor core
9
mounted on this rotating shaft
7
, a field coil
10
wound between both of the rotor cores
8
and
9
, fans
11
and
12
provided in the back of both of the rotor cores
8
and
9
, a pulley
13
provided outside the front bracket
1
side of the rotating shaft
7
, and a slip ring
14
provided inside the rear bracket
2
side of the rotating shaft
7
for supplying a current to the field coil
10
. Numeral
15
is a brush for supplying a current to the slip ring
14
, and numeral
16
is a brush holder for holding this brush
15
, and numeral
17
is a commutator for commutating alternating current output of the stator coil
5
, and numeral
18
is a regulator for regulating a current of the field coil
10
to control an output voltage of the stator coil
5
.
Numerals
19
and
20
are magnetic poles axially extending to the inner diameter of the stator core
4
from the first rotor core
8
and the second rotor core
9
through a predetermined air gap. A plurality of the magnetic poles
19
extending from the first rotor core
8
and the magnetic poles
20
extending from the second rotor core
9
are respectively provided according to the number of poles of the generator and are arranged so as to have engagement alternately through predetermined gaps
21
and
22
between the magnetic poles and are magnetized in north poles and south poles alternately by excitation of the field coil
10
. Also, the magnetic poles
19
and
20
are formed into an isosceles trapezoid whose width is narrowed in the rotational direction toward the top end as shown in
FIG. 17
, and both the end surfaces of the rotational direction are formed in a straight line at a predetermined angle of inclination and thus, a line pitch between centerlines indicated by broken lines of the gaps
21
and
22
between the magnetic poles also changes in a straight line as shown in FIG.
17
.
In order to improve efficiency of the generator generally, the centerlines indicated by the broken lines of the gaps
21
and
22
between the magnetic poles are set so as to incline in the range from about 60° to about 120° where an electrical angle between the adjacent magnetic poles
19
and
20
is set to 180° and, for example, the center of the magnetic pole
19
is set to 0° as shown in FIG.
17
. Also, chamfered parts
19
a
and
20
a
for smoothing a magnetic flux density of the air gap formed between the magnetic poles
19
,
20
and the stator core
4
and suppressing electromagnetic noise are formed in the corner of the outer surface opposite to the stator core
4
of the magnetic poles
19
and
20
and both the end surfaces of the rotational direction.
In the conventional alternating current generator for vehicle formed in this manner, when current is passed through the field coil
10
from a battery (not shown) mounted in the vehicle via the brush
15
and the slip ring
14
, the magnetic poles
19
and
20
are excited alternately in the north pole and the south pole and the rotor
6
is driven by an internal combustion engine through the pulley
13
and thereby, the magnetic poles
19
and
20
give a rotating magnetic field to the stator core
4
and a three-phase alternating current voltage is generated in the stator coil
5
and this alternating current voltage is commutated by the commutator
17
for direct current and electric power is supplied to a load (not shown). Then, the regulator
18
holds an output voltage of the stator coil
5
to a constant value by controlling the passed current of the field coil
10
.
In the alternating current generator for vehicle as described above, the rotating magnetic field given to the stator core
4
by the magnetic poles
19
and
20
is not a complete sine wave but a waveform including higher harmonics, and also an output current given to the load by power generation of the stator coil
5
is a current including higher harmonics. In operation of the generator, electromagnetic attraction force occurs between the magnetic poles
19
,
20
and the stator core
4
due to interaction between the rotating magnetic field including higher harmonics and a magnetic field caused by an output current including higher harmonics, and this electromagnetic attraction force acts as applied vibration force, with the result that the stator core
4
and the magnetic poles
19
,
20
vibrate to cause electromagnetic noise. Especially, a particular higher harmonic component among this electromagnetic noise interferes with quietness in the vehicle as abnormal sound, and various measures of noise have been taken.
For example, a technique disclosed in JP-A-54-134309 is also one of the measures of noise, and this technique notes that change in torque caused by periodic passage of the magnetic poles
19
and
20
arranged at regular pitches through the side of an inner diameter of teeth
4
b
arranged at regular pitches of the stator core
4
shown in
FIG. 16
acts as applied vibration force to the stator core
4
, and noise intends to be reduced by setting arrangement of the magnetic poles
19
and
20
at irregular pitches. According to this technique, the noise resulting from vibration the stator core
4
due to the change in torque is reduced, but the noise resulting from the electromagnetic attraction force between the stator core
4
and the magnetic poles
19
,
20
cannot be reduced. Also, in this technique, for example, since the gaps
21
and
22
between the magnetic poles provided between the magnetic poles
19
and
20
shown in
FIG. 14
are set at irregular pitches, the narrow gaps between the magnetic poles occur, so that there were side effects that a leakage magnetic flux between the magnetic poles
19
and
20
increases and output of the generator decreases.
The invention is implemented to solve such problems, and it is an object of the invention to obtain an alternating current generator for vehicle capable of effectively suppressing occurrence of abnormal sound without decrease in performance by reducing applied vibration force of higher harmonic components which can possibly become noise.
An alternating current generator for vehicle according to the invention comprises a stator core in which a three-phase stator coil is wound and inserted into slots, a first rotor core and a second rotor core which are provided in the side of an inner diameter of this stator core and rotate with a rotating shaft, a field coil for magnetizing these first and second rotor cores in different magnetic poles, and a plurality of magnetic poles which are provided so as to extend to an axial direction of the rotating shaft from the first and second rotor cores and are arranged so as to have engagement alternately through predetermined gaps between the magnetic poles and also are opposite to the surface of the inner diameter of the stator core through an air gap, and by forming these magnetic poles in a stepwise shape having a plurality of parts in the axial direction and setting the respective parts to different w
Adachi Katsumi
Asao Yoshihito
Fujita Masahiko
Kometani Haruyuki
Mitsubishi Denki & Kabushiki Kaisha
Nguyen Tran
Sughrue & Mion, PLLC
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