Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-03-09
2003-09-16
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S208000, C310S071000, C310S051000, C310S091000, C310S156660
Reexamination Certificate
active
06621190
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotor for an automotive alternator, which has a Lundell-type field core, for mounting on an automobile engine, and in particular, relates to a winding configuration for winding onto the Lundell-type field core.
2. Description of the Related Art
FIG. 6
is a cross-section of a conventional rotor for an automotive alternator and
FIG. 7
is a cross-section of part of the rotor shown in FIG.
6
.
In
FIGS. 6 and 7
, a rotor
1
comprises a rotating shaft
11
rotatably supported by a pair of brackets (not shown), a pair of Lundell-type field cores
12
a,
12
b
secured to the rotating shaft
11
, a pair of fans
13
a,
13
b
secured to both axial ends of the field cores
12
a,
12
b,
slip rings
14
secured to one end of the rotating shaft
11
, and a field winding
15
wound onto the field cores
12
a,
12
b.
The field cores
12
a,
12
b
are made of iron, comprise cylindrical base portions
121
a,
121
b
fitted over and secured to the rotating shaft
11
and claw-shaped magnetic poles
122
a,
122
b
plurally projecting from the outer circumferential edges of the base portions
121
a,
121
b,
and are secured to the rotating shaft
11
facing each other such that the end surfaces of the base portions
121
a,
121
b
are in close contact with each other and the claw-shaped magnetic poles
122
a,
122
b
intermesh alternately. The field winding
15
is a copper wire with a circular cross-section and is wound a predetermined number of times onto a bobbin
16
fitted over the outer circumferences of the base portions
121
a,
121
b.
A magnetic flux is generated when an electric current is supplied to the field winding
15
by means of the slip rings
14
and magnetic poles are formed in the field cores
12
a,
12
b
by the magnetic flux.
Inner circumferential tape
17
a
for protecting the winding is wound onto the cylindrical portion
16
a
of the bobbin
16
. Outer circumferential tape
17
c
for protecting the winding is also wound onto the outer circumference of the field winding
15
wound onto the bobbin
16
. In addition, side tape
17
b
is disposed between the lead portion of the field winding
15
and the multi-layered portion of the field winding
15
.
The construction of the field winding
15
will now be explained with reference to
FIGS. 8
to
10
.
The bobbin
16
is made of resin, and as shown in
FIG. 8
, comprises a cylindrical portion
16
a
and a pair of first and second annular flange portions
16
b
projecting perpendicularly from both ends of the cylindrical portion
16
a.
A recessed groove
161
for housing a lead wire
15
a
at the start of the winding is disposed radially in the inner surface of the first flange portion
16
b
so as to extend from the outer circumferential side thereof to the cylindrical portion
16
a.
An anchor portion
16
c
is disposed on an outer circumferential portion of the first flange portion
16
b
in close proximity to the upper end of the recessed groove
161
.
First, the inner circumferential tape
17
a
is wound onto the cylindrical portion
16
a
of the bobbin
16
. Then, the starting portion of the field winding
15
is wound around the anchor portion
16
c,
inserted into the recessed groove
161
, and drawn from the lower end (inner circumferential end) of the recessed groove
161
onto the cylindrical portion
16
a.
At this point, the side tape
17
b
is pasted onto the inner surface of the first flange portion
16
b
so as to cover the lead wire
15
a
at the start of the field winding
15
which is housed in the recessed groove
161
. Then, as shown in
FIG. 9
, the field winding
15
drawn out onto the cylindrical portion
16
a
is lined up in rows at an angle “a” relative to a plane that perpendicularly intersects the axial center of the cylindrical portion
16
a
as it is wound onto the cylindrical portion
16
a.
Then, as shown in
FIG. 10
, when the first layer of the winding is finished, a second layer is lined up in rows at an angle “b” relative to the plane that perpendicularly intersects the axial center as it is wound onto the cylindrical portion
16
a.
In this way, the field winding
15
is wound up layer by layer in order from the bottom of the cylindrical portion
16
a,
and when a predetermined number of layers have been wound, the outer circumferential tape
17
c
is wound onto the outermost circumferential portion. In addition, the multi-layered portion of the field winding
15
is saturated with varnish. For example, when a field winding
15
is wound onto the cylindrical portion
16
a
of a bobbin
16
with an outer diameter of 40 to 60 mm, the outermost diametric dimension of the multi-layered portion on which the outer circumferential tape
17
c
is wound is approximately 70 to 90 mm.
In the rotor
1
constructed in this manner, centrifugal force acts constantly on the field winding
15
during power generation, and even slight gaps and looseness are gradually enlarged, leading to disarray in the winding. Thus, in order to achieve winding without gaps or looseness, it is usual to apply tension to the wire as it is wound onto the bobbin
16
, and with respect to the configuration of the start of the winding, to line up the winding in rows at an angle relative to the plane which perpendicularly intersects the axial center as shown in FIG.
9
.
In the field winding
15
wound in this manner, the winding in the second layer, for example, is wound on top of the winding in the first layer with the angle reversed. Thus, the winding configuration in the field winding
15
assumes a first condition in which the portions of wire in the second layer are positioned in the exact center between the adjacent portions of wire in the first layer (condition in
FIG. 11
which is a cross-section taken along line Q—Q in FIG.
10
), a second condition in which the largest diameter portions of the wire in the first layer and the wire in the second layer are stacked radially (condition in
FIG. 12
which is a cross-section taken along line P—P in FIG.
10
), and intermediate conditions which gradually shift from the first condition to the second condition or from the second condition to the first condition. At that time, the height t
1
of the two layers in the second condition is greater than the height t of the two layers in the first condition.
In a conventional rotor for an automotive alternator constructed in this manner, the field winding
15
, which has a circular cross-section, is wound onto the bobbin
16
at an angle to a plane which perpendicularly intersects the axial center, and therefore a first condition in which the portions of wire in the nth+1 layer are positioned in the exact center between the adjacent portions of wire in the nth layer, a second condition in which the largest diameter portions of the wire in the nth layer and the wire in the nth+1 layer are stacked radially, and intermediate conditions which gradually shift between those conditions.
Thus, one problem is that radial irregularities invariably arise within each lap of the field winding
15
and the configuration of the multi-layered portion thereof consequently has eccentricities, which increases vibrations during high-speed rotation, leading to bending of the rotating shaft
11
or disconnection of the winding connections.
Another problem is that the space factor in the multi-layered portion reaches a peak, precluding increases in output.
An additional problem is that portions of wire in the second condition are in contact with other portions at points, making resistance to vibrations poor and giving rise to disarray in the winding. By touching the root portions of the claw-shaped magnetic poles
122
a,
122
b,
the outside of the multi-layered portion of the field winding
15
serves the role of damping axial vibrations in the claw-shaped magnetic poles
122
a,
122
b,
and therefore disarray in the winding leads to increased electromagnetic noise.
SUMMARY OF THE INVENTION
The present invention aims to solve the above problems and
Adachi Katsumi
Asao Yoshihito
Higashino Kyoko
Mitsubishi Denki & Kabushiki Kaisha
Perez Guillermo
Ramirez Nestor
Sughrue & Mion, PLLC
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