Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-09-07
2002-11-05
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S051000
Reexamination Certificate
active
06476535
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an a.c. generator for vehicle, which is driven by an internal combustion engine of a vehicle.
2. Discussion of Background
When an a.c. generator for vehicle is run, in order to ensure best function, it is necessary to cool an entire generator to be in a certain limit temperature or less. As a method of cooling, a fan is fixed to a disk of a magnetic pole wheel of a rotor and arranged inside a casing so as to be opposite to a winding wire of a stator to dissipate a sufficient heat quantity. Accordingly, a degree of cooling is improved, and an output from the a.c. generator can be increased. However, there is a problem that a large wind noise is generated by a turbulent flow of an air inside the casing. In order to solve this problem, the following has been proposed in a conventional technique.
FIG. 14
illustrates a cross-sectional view of a conventional a.c. generator for a vehicle disclosed in, for example, Japanese Unexamined Patent Publication JP-A-5-161286.
FIG. 15
is a perspective view of a magnetic pole wheel of a rotor of the a.c. generator illustrated in FIG.
14
.
FIG. 16
illustrates an end surface of the magnetic pole wheel illustrated in
FIG. 15
viewed in a direction of an arrow F in FIG.
14
.
FIG. 17
is a cross-sectional view taken along a line I—I illustrated in FIG.
16
.
FIG. 18
is an enlarged view of one of teeth of the magnetic pole wheel.
The a.c. generator has a stator assembly having stator core
4
, formed by laminating metallic thin plates and having a plurality of grooves accommodating stator winding wires
5
. The stator assembly is retained between a front bracket
1
and a rear bracket
2
, which are mutually joined by bolts.
A rotor assembly, including two claw-type magnetic pole wheels
8
and
9
, is mounted on a rotational shaft
7
, wherein a central rotor core (not shown) having induction winding wires is retained between the magnetic pole wheels
8
and
9
. The rotor assembly is engaged with, for example, a spline (not shown) formed in the rotational shaft
7
so as to rotate along with the rotational shaft
7
.
Ends of the induction winding wires are connected to hollow connectors
26
and
27
. The connectors
26
and
27
are respectively connected to corresponding one of two slip rings
14
, respectively being in contact with corresponding one of two brushes
15
through the rotational shaft
7
.
On back surfaces of the magnetic pole wheels
8
and
9
, cooling fins
11
and
12
are respectively fixed. The magnetic pole wheels
8
and
9
respectively have a disk
50
in perpendicular to an axis line of the rotational shaft
7
. In central portions of the disks
50
, a concentric through-hole
51
for inserting the rotational shaft
7
is formed. On outer peripheral edges of the disks
50
, six magnetic pole teeth
52
are monolithically formed. The teeth
52
are arranged with equal intervals, which are inwardly directed toward the other magnetic pole wheel and substantially in parallel with the axis line of the rotational shaft.
The teeth
52
of the magnetic pole wheel
8
are shifted by 30° in their peripheral direction with respect to the teeth
52
of the magnetic pole wheel
9
. The teeth of the magnetic pole wheels are mutually inserted between the opposite teeth. As illustrated in
FIG. 15
, the magnetic pole wheels are shaped like angular magnetic pole crowns having opened ends. Polarities of the magnetic pole teeth
52
of the magnetic pole wheel
8
and of the magnetic pole teeth
52
of the magnetic pole wheel
9
are mutually adverse, wherein consecutive magnetic pole openings, having polarities adverse to those of grooves of the stator of the a.c. generator, are formed.
As illustrated in
FIGS. 15 through 18
, the magnetic pole teeth are shaped like a trapezium when viewed in a direction of the stator. Wide base portions of the teeth are joined to the disks
50
of the magnetic pole wheels. In more detail, the teeth
52
are formed by a cylindrical outer surface
54
, chamfered portions
57
and
59
, and two types of side surfaces
56
and
58
, joined to the outer surfaces
54
.
In directions perpendicular to the disks
50
, the side surfaces
56
and
58
are in parallel with axis of symmetry X—X of the teeth
52
. In regions apart from the disks
50
, the side surfaces
56
and
58
are slanted so as to symmetrically converge into the axis X—X, and joined via the end surface
60
, forming an end portion of the teeth
52
and being in perpendicular to the axis X—X. The outer surface
54
is joined to the back surface
62
of the disk
50
via a slant surface
64
.
The teeth
52
respectively have at least one chamfered portion
66
, functioning to prevent a noise. The chamfered portion is adjacent to the outer surface
54
, and the side surfaces
56
or
58
on one side, and is adjacent to the surface
64
and surface
62
. The chamfered portions
66
for preventing noise are slanted by angles respectively different from degrees of slant of the adjacent surfaces.
However, in the conventional a.c. generator for vehicle, there is a problem that an output is decreased because the chamfered portions
66
are too large.
FIG. 19
is a cross-sectional view of a part of the conventional a.c. generator for vehicle, wherein a flow of a magnetic flux is shown. As designated by an arrow in
FIG. 19
, the flow of the magnetic flux &PHgr; forms a loop from the magnetic pole wheel
8
of the rotor, the stator core
4
, again the rotor, and the magnetic pole wheel
9
of the rotor, to the magnetic pole wheel
8
. If the chamfered portion
66
of the magnetic pole wheel
8
or
9
is increased, the length 1 of a shoulder portion of the magnetic pole wheel
8
, through which the magnetic flux &PHgr; passes, is shortened. Accordingly, a cross-sectional area of the magnetic pole wheel
8
is reduced, therefore the magnetic flux &PHgr; can not sufficiently pass, whereby there are problems that a property of the magnetic circuit is deteriorated, and an output is reduced.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the above-mentioned problems inherent in the conventional technique and to provide an a.c. generator for vehicle, which can reduce noises such as a wind noise and an electromagnetic noise, and can improve a magnetic circuit of a rotor so as to increase a magnetic flux to obtain a high output.
According to a first aspect of the present invention, there is provided an a.c. generator for a vehicle comprising:
a stator core having a stator coil;
a first rotor core, fixed to a rotational shaft inside an inner diameter of the stator core;
a second rotor core, fixed to the rotational shaft inside the inner diameter of the stator core;
a field magnetic coil for magnetizing the first rotor core and the second rotor core; and
a plurality of first magnetic pole pieces and a plurality of second magnetic pole pieces, which are located in an axis direction of the rotational shaft respectively from the first rotor core and the second rotor core so as to mutually engage with a predetermined gap and to be opposite to the inner diameter of the stator core with a predetermined gap,
wherein at least the first magnetic pole pieces or the second magnetic pole pieces has chamfered portions, formed by a surface on three points, being a point on a most outer periphery of a root shoulder portion and on a taper continuing from the most outer periphery toward an outer side of the generator in the axis direction to an end surface of the stator core, a point on a skew slanted portion of the magnetic pole piece, and a point on a surface of the magnetic pole piece apart from the end surface of the stator core by a distance between L
1
/4 and 7×L
1
/8 in the axis direction, where L
1
is a distance between a root end surface of the magnetic pole piece and the end surface of the stator core.
According to a second aspect of the present invention, there is provided the a.c. generator for vehicle according to the first aspect of the p
Asao Yoshihito
Oohashi Atsushi
Mitsubishi Denki & Kabushiki Kaisha
Nguyen Tran
Sughrue & Mion, PLLC
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