Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-04-25
2001-09-18
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S049540
Reexamination Certificate
active
06291921
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automotive alternator in which a voltage is generated in a stator by rotation of a rotor.
2. Description of the Related Art
FIG. 9
is a cross-section of a conventional automotive alternator, and
FIG. 10
is a perspective view of the rotor in FIG.
9
.
This automotive alternator includes: a case
3
composed of an aluminum front bracket
1
and an aluminum rear bracket
2
; a shaft
6
disposed in the case
3
, a pulley
4
being secured to a first end of the shaft
6
; a Lundell-type rotor
7
secured to the shaft
6
; fans
5
secured to both ends of the rotor
7
; a stator
8
secured to an inner wall of the case
3
; 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
moving in contact with the surface of the slip rings
9
; a brush holder
11
accommodating the brushes
10
; a rectifier
12
in electrical contact with the stator
8
for converting alternating current generated in the stator
8
into direct current; and a regulator
18
fitted over the brush holder
11
for adjusting the magnitude of the alternating current generated in the stator
8
.
The rotor
7
includes: a field coil
13
generating magnetic flux on passage of electric current; and a pole core
14
disposed so as to cover the field coil
13
in which magnetic poles are produced by the magnetic flux generated by the field coil
13
. The pole core
14
includes a first pole core body
21
and a second pole core body
22
which are mutually interlocked. The first pole core body
21
and the second pole core body
22
are made of iron, and have tapered claw-shaped magnetic poles
23
and
24
, respectively.
FIG. 11
is a perspective of the stator
8
in
FIG. 9
,
FIG. 12
is a perspective of the stator core
15
in
FIG. 9
, and
FIG. 13
is a partial plan of the stator core
15
.
The stator
8
includes: a stator core
15
laminated from a number of steel plates through which a rotating magnetic field from the field coil
13
passes; and a three-phase stator coil
16
through which generated electric current flows. The stator core
15
includes: an annular core back
82
; and a number of teeth
81
spaced evenly in the circumferential direction and extending radially inwards from the core back
82
. The three-phase stator coil
16
is housed in slots
83
between adjacent teeth
81
. The teeth
81
include: broad end portions
85
extending in a circumferential direction of the stator
8
; and column portions
86
connecting the end portions
85
to the core backs
82
. Spaces called openings
84
are formed between the end portions
85
of adjacent teeth
81
.
FIG. 14
is a circuit diagram for a conventional automotive alternator of the above construction, the stator coil
16
being composed of three windings Y in a three-phase Y-connection. The rectifier
12
includes diodes
123
and
125
.
In an automotive alternator of the above construction, a current is supplied by a battery (not shown) through the brushes
10
and slip rings
9
to the field coil
13
, whereby a magnetic flux is generated, giving rise to a magnetic field. At the same time, the pulley
4
is driven by an engine and the rotor
7
is rotated by the shaft
6
such the stator core
15
is subjected to a rotating magnetic field, electromotive force is generated in the stator coil
16
, and output current is generated by an external load connected to the automotive alternator. The alternating current generated by the stator
8
is converted into a direct current by the rectifier
12
. Moreover, the current flowing through the field coil
13
is controlled by the regulator
18
to adjust the magnitude of the voltage of the alternating current generated by the stator
8
.
In an automotive alternator of the above construction, there are twelve poles in the rotor
7
, and thirty-six slots
83
in the stator core
15
, making one slot
83
per pole per phase, and one problem has been when the dimensions of the openings
84
are reduced in order to reduce the magnetic resistance of an air gap between the stator
8
and the rotor
7
, claw-shaped magnetic poles
23
and
24
overlap the end portions
85
of the same tooth
81
simultaneously when viewed from a radial direction, increasing the amount of ineffective magnetic flux flowing in the end portions
85
as indicated by arrow B and reducing the amount of magnetic flux generated by the field coil
13
being routed through the stator coil
16
, thereby reducing output.
SUMMARY OF THE INVENTION
The present invention aims to solve the above problems and an object of the present invention is to provide an automotive alternator enabling output to be improved by enabling the amount of ineffective magnetic flux flowing through a tooth between adjacent claw-shaped magnetic poles to be reduced and increasing effective magnetic flux.
To this end, according to the present invention, there is provided an automotive alternator comprising a rotor having a flat surface portion extending substantially parallel to a shaft secured to the pole core, the flat surface portion being formed in a root portion of claw-shaped magnetic pole such that when an end portion of a tooth spread in a circumferential direction is positioned between adjacent claw-shaped magnetic poles, there is clearance between the end portion of the tooth and at least one of the claw-shaped magnetic poles when viewed from a radial direction.
According to another aspect of the present invention, there is provided an automotive alternator comprising a rotor having stepped portions extending longitudinally being formed on two side surfaces of the claw-shaped magnetic pole such that when an end portion of a tooth spread in a circumferential direction is positioned between adjacent claw-shaped magnetic poles, there is clearance between the end portion of the tooth and at least one of the stepped portions of the adjacent claw-shaped magnetic poles when viewed from a radial direction.
REFERENCES:
patent: 3714484 (1973-01-01), Habert
patent: 4201930 (1980-05-01), Inagaki et al.
patent: 4972114 (1990-11-01), Frister
patent: 5270605 (1993-12-01), Lefrancois et al.
patent: 5708318 (1998-01-01), Fudono
patent: 7-26345 (1992-01-01), None
Mitsubishi Denki & Kabushiki Kaisha
Nguyen Tran
Sughrue Mion Zinn Macpeak & Seas, PLLC
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