Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-07-24
2001-11-20
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S049030, C310S043000, C310S216006, C310S256000
Reexamination Certificate
active
06320294
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to brushless direct current (DC) motors and, more particularly, to a stator structure and method of manufacture of a claw-pole stator structure for such motors.
One form of brushless DC motor includes a stator structure comprising a pair of opposed, complementary, claw-pole stator members with a stator winding formed on a bobbin and sandwiched therebetween. Each of the stator members comprises a planar base component with a plurality of circumferentially spaced stator poles extending in a normal direction from adjacent a periphery of the base component. A central core member extends from at least one of the base components of each pair and passes through a center of the winding bobbin. A permanent magnet rotor circumscribes the stator structure and is radially spaced therefrom by a small air gap.
Prior art methods of manufacture of claw-pole stators include machining the complementary stator pairs from solid blocks of ferromagnetic material, typically a block of molded magnetic material such as a powdered iron in a plastic matrix. While this method produces a structure with good electrical and magnetic characteristics, the cost of manufacture is generally excessive. Another method that is more economically viable is to form the stator structure by stamping a magnetic metal plate and then bending circumferential extensions of the plate to form the depending magnetic poles. In general, such stamped and bent structures have unsatisfactory electrical and magnetic characteristics. Accordingly, it is desirable to provide a claw-pole, brushless DC motor and method of manufacture which is both economical and has good electrical and magnetic characteristics.
SUMMARY OF THE INVENTION
Among the several objects of the present invention may be noted the provision of an improved claw-pole stator structure; the provision of a claw-pole stator structure and method of manufacture which minimizes material costs; the provision of a claw-pole stator structure having good performance characteristics; and the provision of a method of manufacture of claw-pole stator structures which is relatively simple without deterioration of product performance.
In one form, the invention is illustrated as a multiple pole brushless DC motor stator comprising a pair of complementary opposable claw-pole stator structures, each of the stator structures having a stator base and a plurality of stator pole members extending in a generally normal direction from a plane of a stator base. Each stator base comprises a plurality of stacked sheet metal laminations. Each stator pole comprises a unitary member formed by compression molding of a powdered iron in a plastic matrix or a binderless iron flake. Each of the stator poles is attached at preselected locations about the periphery of the stator base. In one form, the pole members are separately formed and adhesively bonded to the stator base. In another embodiment, the stator base is placed in the bottom of a female die and the powdered or flaked ferromagnetic material is poured into the die and then compression molded in situ to form the stator pole members in which the compression molding process bonds the pole members to the stator base.
The stator base may be formed of a plurality of stamped laminations having peripheral slots at locations at which the stator pole members are to be attached. The slots may be formed as mortises in the laminations. A center core member may also be attached to the stator base either by separately forming the center core and adhesively bonding it to the stator base or by forming the center core in situ in the same manner as forming of the pole members.
In a more specific method, the stator base may be formed by stamping each of a plurality of stator laminations from a sheet of magnetic material. The stator laminations are then stacked to a predetermined height to form the stator base. The laminations may be formed in a conventional design having cutouts or protrusions which allow the laminations to be aligned in a predetermined arrangement and to attach one to another. The stator pole members may be preformed in a conventional compression molding operation and subsequently attached to the stator base by adhesively bonding the stator pole members to the stator base. The laminations may be formed with peripheral slots for receiving the stator poles in predetermined orientations. The slots may be cut in the edges of the laminations or be indented from the edges to form mortises for receiving the stator poles. Alternatively, the stacked laminations forming the stator base may be placed in a female die shaped for receiving a powdered or flaked ferromagnetic material which can be molded to form the stator pole members. A male die having a configuration which mates with the female die and forms the stator pole members in the desired final shape is then brought into operative position with the female die so as to compress the ferromagnetic material into the shape of the stator pole members. By compression molding the stator pole members onto the stacked laminations, the pole members are molded in situ and attached to the stator base. The stator base may be formed with peripheral slots at which the stator pole members are attached by the molding process or be formed with mortises in which the stator pole members are compression molded and attached to the stator base.
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Agosti Ann M.
Breedlove Jill M.
General Electric Company
Nguyen Tran
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