Pivotal structure for a motor rotor

Details Pivotal structure for a motor rotor Pivotal structure for a motor rotor

2000-03-09

2001-06-12

Enad, Elvin (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S089000, C310S090000, C310S0400MM, C417S423120

Reexamination Certificate

active

06246140

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pivotal structure for a motor rotor of, e.g., a miniature heat-dissipating fan that includes a metal axle tube having a bearing mounted therein. An outer periphery of the metal axle tube is engaged with a stator bobbin. The metal axle tube is mounted in place very reliably, thereby allowing stable rotation of the rotor.
2. Description of the Related Art
U.S. Pat. No. 5,492,458 to Alex Horng issued on Feb. 20, 1996 discloses an electric fan includes a housing having a stub
11
formed in the center. A metal axle tube
4
has one end force-mounted in the stub
11
and an annular flange
43
formed in the other end. Two pole plates
30
and
32
are force-fitted on the axle tube
4
, and a stator
3
is disposed between the pole plates
30
and
32
. The metal axle tube
4
has a diameter greater than inner diameter of central holes
34
and
35
of the pole plates
30
and
32
and inner diameter of a central hole
21
in a circuit board
2
. The diameter of the metal axle tube
4
is slightly smaller than that of a central hole
33
of the stator
3
. Nevertheless, it is found that the stub
11
breaks if force mounting between the metal axle tube
4
and the stub
11
is too tight. On the contrary, the metal axle tube
4
will loosen in an undesired manner if the force mounting between the metal axle tube
4
and the stub
11
is too loose.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to provide a pivotal structure for a rotor of a miniature motor, wherein the metal axle tube and the stub on the housing have an optimized engagement therebetween such that the metal axle tube may be firmly secured to the stub. The metal tube receives a bearing therein for pivotally holding the central shaft of the rotor.
It is a secondary object of the present invention to provide a pivotal structure for a rotor of a miniature motor, wherein the central shaft of the rotor may rotate in a stable manner.
In accordance with the present invention, the stub of the housing has a through-hole and includes a ledge formed in a lower portion of the through-hole for supporting a lower end of the metal axle tube that is force-fitted into the stub from top. An expander is inserted into a lower end of the stub and has a stem extended through the ledge and into the lower end of the metal axle tube. Thus, the metal axle tube is expanded radially outward by the stem of the expander and thus securely engaged to the inner periphery defining the through-hole of the stub. An end surface of the stem may support a lower end of the central shaft of the rotor, thereby allowing more stable rotation of the rotor.
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: 4554491 (1985-11-01), Plunkett
patent: 4959571 (1990-09-01), Yasumoto et al.
patent: 5028216 (1991-07-01), Harmsen et al.
patent: 5492458 (1996-02-01), Horng

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