Pole plate structure for a motor stator

Details Pole plate structure for a motor stator Pole plate structure for a motor stator

2001-07-26

2003-01-28

Nguyen, Tran (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S216006

Reexamination Certificate

active

06512319

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pole plate structure for a motor stator. More particularly, the present invention relates to a pole plate structure for a brushless d.c. motor stator that increases the rotating torque of the motor while allowing easy starting of the motor and reducing the cogging torque.
2. Description of the Related Art
A conventional cooling fan motor, as illustrated in
FIGS. 1 and 2
of the drawings, discloses a stator for a brushless d.c. motor comprising an upper pole plate
91
and a lower pole plate
92
respectively mounted to upper and lower ends of a set of windings
93
. Each pole plate
91
,
92
comprises a plurality of vertically extending magnetic pole faces
94
for increasing a rotating torque of the rotor. In order to allow easy starting and avoid dead corners in rotation of the rotor, each magnetic pole face
94
includes a chamfered corner
95
. However, since the permanent magnet of the rotor is comprised of alternatively disposed north poles and south poles and since the rotor is driven by the alternating magnetic fields generated by the stator winding, changes in the rotating torque or uneven rotating torque (the so-called “cogging torque”) occur during a transient change between the north pole and south pole of the permanent magnet of the rotor relative to the magnetic pole faces of the upper and lower pole plates
91
and
92
. As illustrated in
FIGS. 1 and 2
, at least an edge
96
of the magnetic pole face
94
represents a rectilinear line that is perpendicular to a planar surface of the pole plates
91
,
92
, which generates a significant cogging torque during rotation of the rotor. Trembling of the rotor as a result of cogging torque is more obvious when the rotor rotates at low speed.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a pole plate structure for a motor stator having a larger relative induction area between the rotor and the stator magnetic poles to thereby increase the rotating torque of the rotor. In addition, the pole plate structure allows easy starting of the rotor and reduces the cogging torque during rotation of the rotor.
A pole plate for a motor stator in accordance with the present invention comprises a central hole and a plurality of circumferentially regularly spaced sector edges. Each sector edge has a pole face extending in a plane perpendicular to a planar surface of the pole plate. The pole face includes a distal side that is opposite to the respective sector edge. A central line passing through a middle point of the respective sector edge and a middle point of the distal side of the respective pole face are not coincident with and at an angle with a radial line passing through a center of the central hole and the middle point of the respective sector edge.
Other objects, specific advantages, and novel features of the invention will become more apparent from the following detailed description and preferable embodiments when taken in conjunction with the accompanying drawings.


REFERENCES:
patent: 3450913 (1969-06-01), Baker et al.
patent: 4201930 (1980-05-01), Inagaki et al.
patent: 5831359 (1998-11-01), Jeske
patent: 5962947 (1999-10-01), Suzuki et al.
patent: 6031304 (2000-02-01), Suzuki et al.
patent: 6270325 (2001-08-01), Hsieh
patent: 6281616 (2001-08-01), Burgbacher et al.

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