Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-12-26
2004-06-15
Le, Dang (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
Reexamination Certificate
active
06750580
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a permanent magnet positioning and retaining device and in particular relates to a direct current brushless motor, capable of keeping permanent magnets of rotor in place under high-speed revolution.
BACKGROUND OF THE INVENTION
Conventional direct current brushless rotor comprises a rotor iron core, several arc-shaped permanent magnets around said rotor iron core, and a sleeve fit around and over said arc-shaped permanent magnets. Under revolution, the permanent magnets are pulled away in radial direction by centrifugal force so as to lose contact with the rotor iron core, thus creating magnetic impedance and affecting motor performance.
FIG. 1
shows a structural perspective of a sleeved direct current brushless rotor. In order to prevent magnetic flux leakage, gaps
15
and cut-off areas
14
are provided between adjacent arc-shaped permanent magnets
12
. Under revolution, said gaps
15
, however, prevent permanent magnets
12
from remaining in the same position and orientation. This causes instability in torque output and motor efficiency, produces noise and vibration, and affects overall motor performance.
FIG. 2
shows a structural perspective of a magnet positioning and retaining device in accordance with prior art U.S. Pat. No. 5,176,461. Though protrusions
24
provided between two permanent magnets
22
are intended for stopping the permanent magnets
22
from moving in circumferential direction, they are incapable of preventing said magnets
22
from shifting in radial direction. Furthermore, the centrifugal force generated by rotation forces the magnets
22
against the sleeve, causing stress, reducing and motor reliability and lifespan.
U.S. Pat. Nos. 5,828,152 and 6,084,330 are related prior arts with similar disadvantages shared by the embodiment of FIG.
2
.
FIG. 3
shows a structural perspective of a magnet positioning and retaining device in accordance with the improved prior art U.S. Pat. No. 4,954,736. In the figure, the expanded portion
34
of an integral holding projection provided between two permanent magnets
32
fills the gap between two adjacent permanent magnets
32
so as to stop the movement of permanent magnets
32
in the circumferential direction. In addition, the near triangle-shaped structure provided on both ends of the contact region between a sleeve
33
and said expanded portion
34
can prevent radial shifting of permanent magnets
32
. However, the good intention of reducing magnetic flux leakage by the cut-off design of permanent magnets
32
is offset by the use of integrally stamped silicon steel for said expanded portion
34
, being a magnetic conducting material in direct contact with the magnets
32
. Moreover, high cost associated with excess scrap material as a result of stamping process hinders said prior art from becoming commercially competitive.
Another related prior art U.S. Pat. No. 4,910,861 reveals plastic filling for the gap between permanent magnets. Yet in high-speed revolution, the loaded rotor generates heat, which softens plastic fillings and undercut their strength of holding permanent magnets in place. Again, the lifespan and reliability of rotor remain unsatisfactory.
The prior arts and the improved ones as discussed above fail to provide answers for resolving the aforementioned discrepancies. The quest to solutions stays a priority for those skilled in the art.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a permanent magnet rotor magnet positioning and retaining device, capable of preventing circumferential and radial shifting of permanent magnets, thereby ensuring overall motor performance, reliability and lifespan.
Another object of the present invention is to provide a divider made from poor or non-magnetically conducting material for making direct contact with permanent magnets and for preventing magnetic flux leakage.
To that end, the present invention reveals a permanent magnet rotor magnet positioning and retaining device, comprising a sleeve, a rotor iron core, at least one arc-shaped permanent magnet, and a plurality of dividers wherein said sleeve has a hollow tubular structure; said rotor iron core comprises a least one groove circumferentially provided in the proper locations inside said sleeve; said arc-shaped permanent magnets of alternating poles provided between said sleeve and said rotor iron core are separated from one another by said dividers, said arc-shaped permanent magnets each having a cut-off area in outer perimeter corners of two adjacent permanent magnets so as to form a near triangle-shaped region between two adjacent permanent magnets; a plurality of dividers, provided between permanent magnets of alternating poles, comprises a base, a trunk and a rim; wherein said base is engaged with a groove so that the dividers are secured to the rotor iron core; said trunk fills the gap between two adjacent permanent magnets to prevent said permanent magnets from moving in circumferential direction; and said rim has a near triangle-shaped structure in close contact with said cut-off area (in outer perimeter corners of two adjacent permanent magnets) so as to prevent permanent magnets from moving in radial direction.
The following Description and Designation of Drawings are provided in order to help understand the features and content of the present invention.
REFERENCES:
patent: 4855630 (1989-08-01), Cole
patent: 4910861 (1990-03-01), Dohogne
patent: 4973872 (1990-11-01), Dohogne
patent: 5237737 (1993-08-01), Zigler et al.
patent: 5828152 (1998-10-01), Takeda et al.
Chang Yu-Choung
Dummy Ann-Huang
Hsiao Tse-Liang
Lai Ching-Feng
Liang Kun-I
Addison Karen B
Industrial Technology Research Institute
Le Dang
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