Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2003-03-19
2004-08-31
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
Reexamination Certificate
active
06784581
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention is related to a magnetic floating bearing of a fan, in which by means of distribution of magnetic force, the rotary shaft fitted in an inner magnetic ring is restricted within an outer magnetic ring to rotate in a floating state.
A ball bearing or oil-bearing bearing is applied to a fan for reducing resistance against the rotary shaft of the fan. However, when rotated, there is still frictional force exerted onto the shaft to produce noise.
FIG. 1
shows a magnetic floating bearing of a heat-radiating fan. The bearing includes a base seat
80
having an upright sleeve. At least one magnetic hollow cylinder
81
is annularly disposed on inner wall of the sleeve. In addition, at least one magnetic ring
82
is fitted around lower section of the rotary shaft
83
corresponding to the magnetic hollow cylinder
81
. The magnetic ring
82
is repelled downward by the magnetic hollow cylinder
81
. Accordingly, when the rotary shaft
83
is fitted into the upright sleeve, the rotary shaft
83
is kept pulled downward. When rotated, the magnetic ring
82
fitted around the rotary shaft
83
is not in contact with the magnetic hollow cylinder
81
. However, the magnetic ring
82
is repelled downward by the magnetic hollow cylinder
81
so that the rotary shaft
83
is pushed downward and the bottom end
831
of the rotary shaft abuts against upper face of a board
84
. Accordingly, when the rotary shaft
83
rotates, the board
84
will still exert a frictional force against the bottom end
831
of the rotary shaft
83
. This will reduce rotational efficiency. Moreover, after a period of use, the bottom end
831
of the rotary shaft
83
and the board
84
will be worn out and the using life of the fan will be shortened.
FIG. 2
shows another type of conventional magnetic floating bearing structure including a magnetic rotary shaft coupling section
91
fixedly fitted around the rotary shaft
92
and projecting therefrom. The upper and lower ends of the coupling section
91
are formed with slopes
911
. The bearing structure further includes a recessed magnetic locator coupling section
93
fixedly annularly fitted in the locator. The upper and lower ends of the locator coupling section
93
are formed with slopes
931
. The slopes
931
and the slopes
911
of the rotary shaft coupling section
91
magnetically repel each other, whereby the rotary shaft
92
is rotatably restricted within a certain range. However, the slopes
911
of the rotary shaft coupling section
91
and the slopes
931
of the locator coupling section
93
must have equal inclination angle so as to exert equal upward and downward axial forces F
1
, F
2
onto the rotary shaft
92
and make the rotary shaft coupling section
91
float between the locator coupling sections
93
. Accordingly, the rotary shaft
92
can rotate without suffering frictional force. However, the manufacturing and assembling procedure of the magnetic floating bearing necessitates high precision so that the manufacturing cost is relatively high. Moreover, the rotary shaft coupling section
91
radially floats between the locator coupling sections
93
simply by means of the transverse component force created between the inner and outer slopes
911
,
931
. The transverse centrifugal force created when the fan rotates is the main force applied to the bearing. The transverse component force is quite limited and there is no support around the rotary shaft coupling section
91
. Therefore, simply relying on the little transverse component force created between the inner and outer slopes
911
,
931
, the rotary shaft can hardly bear the transverse force when rotating at high speed. As a result, the rotary shaft will inevitably transversely severely shake.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to provide a magnetic floating bearing of a fan, which locates rotary shaft by means of distribution of magnetic force. The magnetic floating bearing includes: an outer magnetic ring formed with a central axial through hole, an upper and a lower ends of the wall of the through hole having a magnetic strength greater than that of a center of the wall; and an inner magnetic ring formed with a central axial fitting hole in which a rotary shaft is snugly fitted, the polarity of an outer circumferential wall of the inner magnetic ring being identical to the polarity of the wall of the through hole of the outer magnetic ring, an upper and a lower ends of the outer circumferential wall of the inner magnetic ring having a magnetic strength less than that of a center of the outer circumferential wall. The upper and lower ends of the wall of the through hole of the outer magnetic ring respectively exert greater magnetic repelling force onto the center of the outer circumferential wall of the inner magnetic ring. Therefore, the inner magnetic ring is rotatably restricted and located within the outer magnetic ring without upward or downward detaching therefrom.
The present invention can be best understood through the following description and accompanying drawings wherein:
REFERENCES:
patent: 5280208 (1994-01-01), Komura
patent: 54-1339007 (1979-10-01), None
patent: 361269118 (1986-11-01), None
patent: 401260301 (1989-10-01), None
Chen Cheng-Kang
Yu Chien-Chun
Mohandesi Iraj A.
Mullins Burton S.
Rosenberg , Klein & Lee
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