Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1997-10-29
2002-05-07
Tamai, Karl (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S263000
Reexamination Certificate
active
06384506
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a bobbin unit for holding the field coil of a brushless alternator.
2. Description of the Related Art
FIG. 13
is a sectional view showing a conventional brushless alternator for a vehicle taken along the axial direction thereof,
FIG. 14
is an upper plan view of the iron core of a conventional bobbin unit,
FIG. 15
is a sectional view taken along the line XV—XV of
FIG. 14
,
FIG. 16
is an upper plan view of the plate of the conventional bobbin unit,
FIG. 17
is a sectional view taken along the line XVII—XVII of
FIG. 16
,
FIG. 18
is an upper plan view of the bobbin of the conventional bobbin unit,
FIG. 19
is a sectional view taken along the line XIX—XIX of
FIG. 18
,
FIG. 20
is a backside plan view of the bobbin and
FIG. 21
is a sectional view of the main portion of the bobbin unit showing how an iron core is connected to a plate by spot welding.
In
FIG. 13
, a brushless alternator
1
is arranged such that a field coil
2
does not rotate and a bobbin unit
6
which holds the field coil
2
is fixed to the rear bracket
7
of the alternator, and is different from an alternator with a rotary field type brush. An N-pole rotor core
8
and an S-pole rotor core
9
are rotated together with a shaft
10
.
The bobbin unit
6
is composed of an approximately cylindrical iron core
3
as a field iron core forming a magnetic circuit, a thin wall plate
4
connected to the iron core
3
by spot welding and a resinous bobbin
5
interposed between the iron core
3
and the plate
4
for accommodating the field coil
2
.
As shown in FIG.
14
and
FIG. 15
, the iron core
3
is formed of a cylindrical thick wall portion
3
a
having a thick wall and a thin wall portion
3
b
projecting from the minimum radius portion of the thick wall portion
3
a
along the periphery thereof. The iron core
3
is made by being machined from a round steel bar by turning. On the other hand, the plate
4
is stamped from a mild steel sheet and composed of a cylindrical portion
4
a
formed to a cylindrical shape and a flange portion
4
b
formed from one end of the cylindrical portion
4
a
so as to spread outwardly of the radial direction thereof is shown in FIG.
16
and FIG.
17
. Cutouts
4
c
, which position a bobbin
5
to be described later and with which the projections of detents are engaged, are formed to the outer periphery of the flange portion
4
b.
As shown in
FIG. 18
to
FIG. 20
, the bobbin
5
is formed of an approximately-thread-spool-shaped cylindrical portion
5
a
formed to a cylindrical shape and flange portions
5
b
,
5
c
formed at both the ends of the cylindrical portion
5
a
. Projections
5
d
which are engaged, as detents, with the cutouts
4
c
of the plate
4
are formed to the outer periphery of the flange portion
5
c
on one side. On the other hand, a projection
5
e
having a through hole at the center thereof is formed to the outer periphery of the flange portion
5
b
on the opposite side and serves as a detent also acting as a port through which an electric cable is drawn out. Further, four through holes
5
f
are defined along the circumference of the cylindrical portion
5
a
at the intervals of 90°. The through holes
5
f
are defined to permit electric poles to pass therethrough when the iron core
3
is connected to the plate
4
by spot welding.
The conventional bobbin unit
6
arranged as described above is assembled in such a manner that, first, the cylindrical portion
4
a
of the plate
4
is inserted into the bobbin
5
and positioned thereto by the engagement of the projections
5
d
with the cutouts
4
c
. Next, the end of the cylindrical portion
4
a
opposite to the flange portion
4
b
is mounted to the thin wall portion
3
b
of the iron core
3
and the thin wall portion
3
b
and the cylindrical portion
4
a
are clamped by a pair of electrodes disposed on the bobbin
5
side and the inner peripheral side of the thin wall portion
3
b
and spot welded, so that the iron core
3
is connected to the plate
4
. Thereafter, a not shown tape is wound around the cylindrical portion
5
a
of the bobbin
5
for clogging the through holes
5
f
in order to prevent the short circuit of the field coil
2
.
In the conventional bobbin unit
6
arranged as described above, the field coil
2
is wound around the bobbin
5
of the bobbin unit
6
and fixed to the rear bracket
7
of the brushless alternator
1
.
In general, since the smaller winding diameter of the field coil
2
can shorten the length of a copper wire even if the wire has the same number of turns, a cost can be reduced. Therefore, it is effective that the cylindrical portion
5
a
of the bobbin
5
has a diameter as small as possible. In the conventional bobbin unit
6
, however, since the thin wall portion
3
b
is required to the iron core
3
to execute the spot welding, the diameter of the cylindrical portion
5
a
of the bobbin
5
is increased by the thickness of the thin wall portion
3
b
. In addition, the thin wall portion
3
b
needs a predetermined length in an axial direction and must be formed to an accurate cylindrical surface. Further, since the thin wall portion
3
b
has a thin wall thickness, the iron core
3
is machined by turning from a round steel bar and the thin wall portion
3
b
is formed by removing an unnecessary portion from the round steel bar. As a result, a large amount of the steel bar is removed by the turning, by which the material and time are wasted. Further, workability is not good because the field coil
2
is wound after the iron core
3
is connected to the plate
4
.
In addition, the through holes
5
f
must be defined to the bobbin
5
for spot welding and further the tape must be wound to clog the through holes
5
f.
An object of the present invention made to solve the above problem is to provide a bobbin unit for a brushless alternator field coil which can reduce the diameter of a bobbin, need not wind a tape and can be made easily and a method of assembling the bobbin unit.
SUMMARY OF THE INVENTION
A bobbin unit for a brushless alternator field coil according to one embodiment comprises a ring-shaped iron core having a thick wall; a plate which has a cylindrical portion and a flange portion, the cylindrical portion is formed to a thin cylindrical shape having a hole whose inside diameter is as large as the center hole of the iron core and the end of one side of the cylindrical portion is abutted against and connected by butt connection means to the end surface of the iron core on one side thereof with the axial center of the cylindrical portion being in coincidence with that of the iron core, and the flange portion extends outwardly in a radial direction from the end of the cylindrical portion on the other side thereof; and a resinous bobbin disposed in the space formed by the end surface of the iron core on the one side thereof and the outer peripheral surface of the plate for insulating and accommodating a field coil.
A bobbin unit for a brushless alternator field coil according to another embodiment is arranged such that the iron core includes a concentric circular engaging portion formed to the end surface on the side thereof, and the cylindrical portion is connected and the cylindrical portion is connected to the iron core by butt connection means with the end on the one side thereof being engaged with the engaging portion.
A bobbin unit for a brushless alternator field coil according to yet another embodiment is arranged such that the butt connection means is butt welding.
A bobbin unit for a brushless alternator field coil according to still another embodiment is arranged such that the butt connection means is projection welding.
A bobbin unit for a brushless alternator field coil according to still another embodiment is arranged such that the butt connection means is beam welding.
A bobbin unit for a brushless alternator field coil according to still another embodiment is arranged such that the butt connection means is an adhesive.
A method
Kojima Kenta
Sakane Yukio
Sughrue & Mion, PLLC
Tamai Karl
LandOfFree
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