Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2003-02-20
2004-05-18
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S216055
Reexamination Certificate
active
06737782
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electric rotary machine (hereinafter referred to as “rotary machine,” or occasionally “motor” as appropriate), and more particularly to a radial gap type rotary machine comprising an armature with discrete salient poles.
2. Description of the Related Art
In a conventional rotary machine including a stator armature structured such that a plurality of ring-shaped yoke pieces, which are made of a soft magnetic plate, such as a silicon steel plate, and which each have a plurality of pole tooth portions protruding radially, are stacked in the axial direction, since each of the ring-shaped yoke pieces is punched out integrally with the plurality of pole tooth portions as a single piece (the armature composed of the ring-shaped yoke pieces thus structured is hereinafter referred to as “integral armature” as appropriate), pole teeth each composed of a stack number of pole tooth portions are not partitioned structurally and therefore a resultant armature will have superior magnetic efficiency (low reluctance). However, in a small rotary machine, since a wire is usually wound directly on each of the pole teeth, the integral armature makes the winding operation troublesome, and extremely troublesome when the rotary machine is of inner rotor type. As a result, the winding operation takes a long time, and the winding incurs unsatisfactory space factor as well. And, due to the flyer-winding involved in this case, the wire is subject to torsional stress during the winding operation, thereby failing to ensure reliability of the winding area.
Under the circumstances above described, a rare earth magnet having high energy product has been developed recently, and the structure of a rotary machine can be reviewed by means of magnetic circuit analysis using a computer. This works to enable a rotary machine with an armature of discrete salient pole structure (this armature is hereinafter referred to as “discrete armature” as appropriate) to obtain requisite motor characteristics. The rotary machine with the discrete armature may give some undesired increase in reluctance but offers great advantages of easier winding operation and increased space factor of winding so as to override the disadvantageous increase in reluctance. From this, it is now realized that the rotary machine with the discrete armature produces higher performance and is manufactured less expensively on the whole, and there is a growing demand for the discrete armature.
One example of the discrete armature is manufactured such that pole tooth portions are dismembered off its main body portion of an integral armature, a wire is wound around each of the dismembered pole tooth portions thereby constituting each salient pole portion, and that the pole tooth portions each with a wire wound therearound, namely, the salient pole portions are rejoined to the main body portion by laser-welding, or the like.
The armature thus structured, however, has a disadvantage that the integral armature has to be first sectioned and later reassembled, thereby requiring an additional time. Also, when the pole tooth portions each with a winding (salient poles) are rejoined to the main body portion, the stack layers of the both portions have to be matched with each other, and therefore it is required that respective portions be held together by a well-maintained tool and surely welded plate by plate for ensuring precision, which results in decreased workability. And, joints (welded portions) deteriorate significantly in mechanical strength and magnetic characteristics.
To overcome the above described problems, the present inventors disclosed in Japanese Patent Application Laid-open No. 2001-238377 a radial gap type rotary machine including a stator which comprises: a discrete armature including a plurality of discrete salient poles, and a cylindrical pole tooth ring for connecting the salient poles to one another magnetically and mechanically; and a cylindrical stator ring adapted to decrease leakage flux resulting from magnetic discontinuity.
FIG. 10
is a partial cross-sectional view of a conventional rotary machine with a discrete armature viewed from the axial direction. Illustrated in
FIG. 10
are: salient poles
106
, an armature assembly
110
, a flange
12
, a rotor assembly
20
, a shaft
21
, pole teeth
134
, bobbins
136
, bobbin flanges
136
b
and
136
c
, coil winding portions
136
g
, magnetic wires
138
, a molding resin
60
, and a stator ring
100
. The rotary machine disclosed in the above mentioned Japanese Patent Application Laid-open No. 2001-238377 has a pole tooth ring for positioning and fixing salient poles, but the pole tooth ring is not essential for the prevent invention and is omitted in
FIG. 10
for ease of understanding. However, it is noted that the present invention can be applied to a rotary machine having the pole tooth ring.
As shown in
FIG. 10
, in the conventional rotary machine with a discrete armature, the bobbin
136
, which holds a pole tooth comprising a plurality of thin steel plates stacked, has its flanges
136
b
and
136
c
respectively on its both ends sandwiching the coil winding portion
136
g
. The bobbin flanges
136
b
and
136
c
are dimensioned to be larger than the coil winding thickness so as to keep the magnet wire
138
braided in good shape. And, the molding resin
60
is injected between the salient poles
106
, whereby the salient poles
106
and the magnet wires
138
are fixed securely. The above described rotary machine, however, has the following problems.
The circumferential dimension of the bobbin flange
136
b
positioned toward the stator ring
100
is usually determined according to the coil winding thickness. The magnet wire
138
receives a stress due to the expansion and contraction of the molding resin
60
injected between the salient poles
106
, and may become unbraided at its outer turns when the bobbin flange
136
b
is conventionally dimensioned, which allows a part of the magnet wire
138
to get in direct contact with the stator ring
100
of a steel plate, possibly causing an insulation failure.
Also, the bobbin flange
136
b
has a dimensional problem, which will be described with reference to
FIGS. 11A
,
11
B and
12
.
FIG. 11A
is a cross-sectional view of a bobbin of the salient pole
106
, in which the bobbin flange
136
b
positioned toward the stator ring
100
is dimensioned to the outside dimension of a coil, and
FIG. 11B
is a cross-sectional view of a bobbin of a salient pole
206
, in which a bobbin flange
236
b
positioned toward the stator ring
100
is dimensioned to be larger than the outside dimension of a coil.
Referring to
FIG. 11B
, the bobbin flange
236
b
dimensioned to be larger than the outside dimension of a coil is forced to be located closer to another bobbin flange
236
c
due to the stator ring
100
arcing, thereby decreasing a winding space for a magnet wire
238
. This means that, if a bobbin flange positioned toward the stator ring
100
is simply increased in dimension as shown in
FIG. 11B
for the purpose of preventing the coil from getting unbraided resulting in a magnet wire coming in contact with the stator ring
100
, the winding space is decreased resulting in a reduced space factor, thereby failing to achieve desired motor characteristics. Seemingly, this problem can be solved by making the bobbin flange
236
b
configured, specifically, arced to the configuration of the inner circumferential surface of the stator ring
100
, but this seeming solution still has the following problem.
FIG. 12
is an explanatory view of the problem of the seeming solution. In
FIG. 12
, a salient pole
306
has a bobbin with a bobbin flange
336
b
located toward the stator ting
100
(not shown in FIG.
12
). The bobbin flange
336
b
has an increased dimension, and is arced to follow the inner circumferential surface of the stator ring
100
. With this configuration, a coil winding portion
336
g
defined by a space between the bobbin flange
336
b
Hata Masato
Matsuura Seiichi
Suzuki Yuzuru
Fay Sharpe Fagan Minnich & McKee LLP
Minebea Co. Ltd.
Nguyen Tran
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