Anti-loosening outer rotor means for high-torque outer-rotor type electric motor

An anti-loosening outer rotor device, adapted for use in an outer-rotor type electric motor, includes: a cylinder member having a plurality of recesses radially recessed in an inside wall of the cylinder member; a magnetic conductor annularly secured to the inside wall of the cylinder member to be circumferentially disposed about an inner stator of the motor and having a plurality of protrusions radially protruding outwardly from the magnetic conductor with each protrusion of the magnetic conductor engaged with each recess of the cylinder member for a firm coupling of the magnetic conductor in the cylinder member for preventing loosening of the magnetic conductor from the cylinder member under high-speed and high-torque rotation; and an end plate secured with the cylinder member for outputing kinetic force of the motor directly from the cylinder member, or for outputing the kinetic force from a driving shaft as axially connected to the cylinder member.

BACKGROUND OF THE INVENTION 
The present invention is an improvement of U.S. patent applications 
(hereinafter defined as "prior arts") also filed by the same inventor of 
this application, including U.S. Ser. No.: 09/320,857, filed on: May 26, 
1999 and U.S. Ser. No.: 09/329,175, filed on: Jun. 9, 1999, etc. 
The prior arts disclosed an outer-rotor type electric motor, as shown in 
FIG. 16 as accompanied in this application, including: an inner stator 1 
fixed on a stator holder 2, and an outer rotor 3 rotatably 
circumferentially disposed about the inner stator 1 about an axis X. The 
outer rotor 3 includes: a cylinder member 31 and a magnetic conductor 30 
secured to an inside wall of the cylinder member 31, having an interface I 
cylindrically defined between the magnetic conductor 30 and the cylinder 
member 31 without intermeshing the conductor 30 and the cylinder member 
31. Such a smooth interface I may cause loosening or separation of the 
magnetic conductor 30 from the cylinder member 31, thereby easily damaging 
or deteriorating the electric motor. 
The present inventor has found the drawbacks of the prior arts and invented 
the present anti-loosening outer rotor device for an outerrotor type 
electric motor with high torque output. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide an anti-loosening outer 
rotor device, adapted for use in an outer-rotor type electric motor, 
including: a cylinder member having a plurality of recesses radially 
recessed in an inside wall of the cylinder member; a magnetic conductor 
annularly secured to the inside wall of the cylinder member to be 
circumferentially disposed about an inner stator of the motor and having a 
plurality of protrusions radially protruding outwardly from the magnetic 
conductor with each protrusion of the magnetic conductor engaged with each 
recess of the cylinder member for a firm coupling of the magnetic 
conductor in the cylinder member for preventing loosening of the magnetic 
conductor from the cylinder member under high speed and high torque 
rotation; and an end plate secured with the cylinder member for outputing 
kinetic force of the motor directly from the cylinder member, or for 
outputing the kinetic force from a driving shaft as axially connected to 
the cylinder member.

DETAILED DESCRIPTION 
As shown in FIGS. 1.about.5, the outer rotor means 3 of an outer-rotor type 
electric motor of the present invention comprises: a cylinder member 31, a 
magnetic conductor 30 annularly secured to an inside wall in the cylinder 
member 31 and an end plate 32 secured to an end portion of the cylinder 
member 31. The magnetic conductor 30 may be a magnet or formed from other 
magnetically conductive materials. 
The cylinder member 31 includes: an inside wall 311 defining a cylindrical 
inner hole 310 about an axis X longitudinally formed at a center of the 
outer rotor means 3, a plurality of recesses 312 radially and 
equally-spaced recessed in the inside wall 311, ad an outside wall 314 
opposite to the inside wall 311 formed on an outside surface of the 
cylinder member 31. 
The magnetic conductor 30 is generally formed as an annular ring and 
includes a plurality of magnetic poles (N or S poles) radially formed on 
the conductor 30, each magnetic pole corresponding to a magnetic-pole 
central angle .theta.. If the number of the magnetic poles is "n", each 
magnetic-pole central angle .theta. will be 360.degree./n. Accordingly, if 
there are eight magnetic poles radially formed in the magnetic conductor 
30, each magnetic-pole central angle .theta. will be obtained as: 
.theta.=360.degree./8=45.degree.. Each central angle has an arc length 
equally divided along a perimeter of the inside wall of the inner hole 
301. 
Each recess 312 recessed in the cylinder member 31 has a chord C defining a 
central angle A about the axis X as shown in FIGS. 2, 4, with the central 
angle A being smaller than the magnetic-pole central angle .theta., 
namely, A&lt;.theta. (FIGS. 1.about.5). 
The magnetic conductor 30 is formed with an inner hole 301 cylindrically 
shaped and rotatably circumferentially disposed about an inner stator (not 
shown) about the axis X; and a plurality of protrusions 303 radially 
protruding outwardly from an outer peripheral surface 302 of the conductor 
30 opposite to the inner hole 301 and equally spaced along the outer 
peripheral surface 302 of the conductor 30; with the outer peripheral 
surface 302 engageable with the inside wall 311 of the cylinder member 31; 
and each protrusion 303 of the magnetic conductor 30 engageable with each 
recess 312 in the cylinder member 31. 
Each protrusion 303 is formed as an arcuate protrusion radially protruding 
outwardly from the magnetic conductor 30, having a chord C defined on an 
arc of each said protrusion 303 equal to the chord C defined on an arc of 
each said recess 312 in said cylinder member 31. Each protrusion 303 or 
its chord C defines a central angle A between the chord C and the axis X. 
Such a central angle A of the magnetic conductor 30 is equal to the 
central angle A of each recess 312 formed in the cylinder member 31. The 
central angle A of each protrusion 303 or recess 312 is smaller than the 
magnetic-pole central angle .theta. defined by each magnetic pole in the 
magnetic conductor 30 (FIGS. 1.about.5). 
Each protrusion 303 has an apex 303c located at a top center convex 
upwardly from the outer peripheral surface 302 of the magnetic conductor 
30, with the apex 303c coinciding with a central line L dividing each 
magnetic-pole central angle .theta. into two half magnetic-pole central 
angles (2.times..theta./2). 
Each recess 312 has a valley center (or a lowest point) 312c located at a 
center of each recess 312 radially recessed in the cylinder member 31, 
with each valley center 312c of each recess 312 of the cylinder member 31 
engageably matching with each apex 303c of each protrusion 303 of the 
magnetic conductor 30 and coinciding with a central line L dividing each 
magnetic-pole central angle .theta. into two half magnetic-pole central 
angles (2.times..theta./2), especially as shown in FIG. 4. 
The number, dimensions, and shapes of the recesses 312 or the protrusions 
303 are not limited in the present invention. 
The magnetic conductor 30 may be integrally formed as an annular magnet or 
magnetic conductor. Or, there are a plurality of arcuate magnet units 30a 
radially divided about the axis X and annularly connected with one another 
to form an annular ring of magnetic conductor 30 as shown in FIG. 5; each 
arcuate magnet unit 30a corresponding to a magnetic pole (N or S pole), 
and every two neighboring magnet units 30a having magnetic poles differing 
each other (for instance, N, S, N. S . . . ). 
Due to the engagement of each convex protrusion 303 of the magnetic 
conductor 30 with each concave recess 312 of the cylinder member 31, the 
magnetic conductor 30 will be steadily stably secured to the cylinder 
member 31 to prevent from loosening or separation of the magnetic 
conductor 30 from the cylinder member 31, thereby being suitable for use 
in an electric motor of outer rotor type having a high torque and high 
speed rotation of the motor. The magnetic conductor 30 and the cylinder 
member 31 may be well connected by adhesive bonding, soldering or any 
other joining methods for further enhancing their firm connection. 
The end plate 32 includes: a central neck (or hub) portion 321 for 
connecting a driving shaft or for coupling an axle (not shown), and a 
short cylindrical extension 322 concentrically formed on a rim portion of 
an inside wall of the end plate 32 to be engaged with a cylindrical hole 
313 formed in an end portion of the cylinder member 31 for securing the 
end plate 32 on the cylinder member 31 by welding or rivetting or other 
joining methods. The cylinder member 31 may be formed with a transmission 
device (not shown) for outputing a kinetic force of the motor directly 
from the cylinder member 31. Or, the kinetic force of the motor is output 
through the shaft axially secured to the central neck portion 321 of the 
end plate 32 which is fixed on the cylinder member 31. 
As shown in FIGS. 6.about.10, each protrusion 303 and each recess 312 
respectively has a chord C defining a central angle, which is equal to 
each magnetic-pole central angle .theta., about the axis X. By the way, 
the number of the protrusions 303 (or the number of the recesses 312) is 
equal to the number of magnetic poles of the magnetic conductor 30 in this 
preferred embodiment. The magnetic conductor 30 may be integrally formed, 
or may be annularly formed by joining a plurality of magnet units 30a as 
shown in FIG. 10. 
As shown in FIGS. 11.about.15, each recess 312 is modified to be an angular 
recess, particularly a triangular recess having a base length or chord C, 
and each protrusion 303 is modified to be an angular protrusion, 
particularly a triangular protrusion having a base length or chord C, with 
each said triangular protrusion 303 engageable with each said triangular 
recess 312 for firmly coupling the magnetic conductor 30 in the cylinder 
member 31. The apex 303c of the protrusion 303 is also engageably matching 
with the valley center (or lowest point) 312c of the recess 312. The 
central angle defined by the chord C of each triangular protrusion 303 or 
recess 312 is equal to each magnetic-pole central angle .theta.. 
Although each central angle A of each protrusion 303 of the magnetic 
conductor 30 or each recess 312 of the cylinder member 31 may be equal to 
or small than each magnetic-pole central angle .theta. as aforementioned. 
However, the degrees of the central angle A of each protrusion 303 or 
recess 312 are not limited in this invention. 
The present invention may be modified without departing from the spirit and 
scope of the present invention. 
The outer rotor of the present invention may interact with an inner stator 
(not shown) to cause rotation of the outer rotor due to armature reaction 
between the inner stator and the outer rotor for outputing work of the 
motor, which is so conventional and not described in detail in this 
invention.