Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-11-09
2004-03-23
Mullins, Burton (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S044000, C310S054000, C310S061000, C310S261100
Reexamination Certificate
active
06710498
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority of Korean Patent Application 1999-49704, filed Nov. 10, 1999 and Korean Patent Application 2000-04587, filed Jan. 31, 2000.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a squirrel cage rotor for induction motors, and more particularly to a squirrel cage rotor that has a polymer resin part containing powder of high magnetic permeability.
In addition, the present invention relates to a method of fabricating the squirrel cage rotor using jig so as to prevent the conductor bars from being buckled.
2. Description of the Prior Art
In a rotating body such as a rotor of a motor, a centrifugal force is generated in proportion to the mass of the rotor and the square of the rotational speed of the rotor, so that the rotor with high rotating speed may have, excessive deformation due to a large stress by the centrifugal force.
The quality of machined products mainly depend on the precision of machine tool which is equipped with built-in type spindle system that is composed of the rotor of motor and the spindle shaft, but the heavy mass of rotor can deteriorate dynamic stability of the built-in type spindle system because the heavy mass of rotor may cause excessive stress and deformation. Therefore, it is important to reduce the inertial force of the rotor by reducing mass of rotor.
The rotating speed of a built-in type spindle generally is restricted by a DN value (where D is a bearing nominal diameter in mm and N is the revolutions per minute of the spindle) and the critical whirling vibration frequency of the spindle. In particular, in the case of a built-in type spindle which is composed of the spindle shaft and the rotor of motor, the bending natural frequency is largely influenced by the mass of the rotor of a motor. Accordingly, as the mass of the rotor of a motor is increased, the bending natural frequency of a built-in type spindle is decreased, thus the heavy mass of rotor limits the maximum rotating speed of the built-in type spindle.
Accordingly, for a built-in type spindle rotating at high speed, it is necessary to increase the specific bending stiffness of the built-in type spindle shaft or decrease the mass of the rotor of a motor.
A conventional squirrel cage rotor is illustrated, in
FIGS. 1 and 2
.
As depicted in
FIGS. 1 and 2
, this conventional squirrel cage rotor includes a rotating shaft
11
. A silicon steel rotor
12
is fitted around the rotating shaft
17
. The silicon steel rotor
12
is fabricated by stacking a plurality of silicon steel sheets
14
. Plurality of conductor bars
16
are respectively inserted into the holes
13
and then the two end rings
17
are fabricated by die-casting. Therefore, the conductor bars
16
are short-circuited by two end rings
17
that are positioned at both ends of the silicon steel rotor
12
.
Since this conventional squirrel cage rotor has heavy mass due to the high density of silicon steel not only a large centrifugal force is generated inside of rotor body, but also is high torque is required to drive the motor.
In order to solve above problems, Korean Pat. Appln. No. 98-50187 discloses “Composite squirrel cage rotor with magnetic powders and method for fabricating it”.
With reference to
FIGS. 3
a
and
4
, the invention of this patent is described in detail.
As shown in
FIGS. 3
a
and
4
, a composite squirrel cage rotor
20
is composed of a composite pipe
22
, a rotating shaft
21
and a squirrel cage conductor
23
which is positioned around the pipe
22
and provided with a plurality of slots
24
. A plurality of heat pipes
25
may be inserted into the slots
24
, respectively.
In this case, the pipe
22
is, fabricated by stacking and curing of composite prepregs which is composed of polymer resin and high strength and modulus fibers. In this case, the pipe
22
is made of fiber reinforced composite material whose polymer resin contains powder of high magnetic permeability such as iron powder in order to improve the performance of the motor.
As depicted in
FIG. 3
a
, this squirrel cage conductor
23
is made of copper or aluminum having high electric conductivity. Plurality of slots
24
are machined along the axis of the squirrel cage conductor
23
by using an end mill or an electric discharge machine tool or a laser machine tool. Each of the slots
24
is formed to be straight along the axis or have a certain angle with the axis. The slots
24
are spaced apart from one another by predetermined regular intervals. In this case, conductor bars and two end rings are integrated into a single squirrel cage conductor
23
.
However, this squirrel cage conductor
23
has a problem of high machining cost. In order to solve this problem, another composite squirrel cage rotor
30
is proposed as shown in
FIGS. 5 and 6
. This composite squirrel cage rotor
30
includes, two end rings
37
. A plurality of holes are formed in each of the end rings
37
and the both ends of the same number of conductor bars
38
are inserted into holes of two end rings
37
by interference fit, with appropriate axial load.
The conductor bars
38
are made of copper or aluminum because copper and aluminum, have high electric conductivity. But since copper or aluminum has low stiffness, the conductor bars
38
which have small diameter relative to the axial length are easily buckled by an excessive axial load during the assembly of the squirrel cage conductor.
After the polymer resin part is cured, the squirrel cage conductor combined with the polymer resin part is ground in order to expose the small portion of the conductor bars
38
on its outer surface. If the conductor bars
38
have been buckled, the exposed areas of the conductor bars
38
are not uniform along the axis of the squirrel cage rotor. This may to cause the performance deterioration of the composite squirrel cage rotor.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been considered the above problems occurring in the prior art, and an object of the present invention is to provide a squirrel cage rotor, which has a polymer resin part containing powder of high, magnetic permeability so that the rotor has low mass.
Another object of the present invention is to provide a squirrel cage rotor having a polymer resin part containing powder of high magnetic permeability, which is provided with a plurality of heat pipes to dissipate heat generated by induction operation between the stator and the rotor of motor.
A further object of the present invention is to provide a method for fabricating a squirrel cage conductor, which prevents conductor bars from being buckled.
In order to accomplish the above objects, the; present invention provides a squirrel cage rotor, comprising: a rotating shaft; a polymer resin part containing powder of high magnetic permeability; and a squirrel cage conductor made of material having high electric conductivity and positioned around the outer portion of the polymer resin part; wherein the powder of high magnetic permeability has a role of increasing the flux density of rotor and is uniformly distributed in the polymer resin part.
In accordance with a feature of the present invention, the slots of the squirrel cage conductor are provided with a plurality of heat pipes, respectively.
In accordance with a feature of the present invention, the rotor further comprises an inner core of high magnetic permeability so as to guide the magnetic flux from the stator to the rotor of motor.
In accordance with a feature of the present invention, chopped fibers are added to the polymer resin part so as to improve mechanical properties such as thermal stability and stiffness.
In addition, the present invention provides a method for fabricating a squirrel cage rotor, the rotor having a rotating shaft, a plurality of conductor bars, two end rings and a polymer resin part containing powder of high magnetic permeability, comprising the steps of: surrounding each of the conductor bars by a pair of jig; inserting the ends of the conducto
Chang Seung Hwan
Lee Dai Gil
Jaeckle Fleischmann & Mugel LLP
Korea Advanced Institute of Science and Technology
Mullins Burton
LandOfFree
Polymer composite squirrel cage rotor with high magnetic... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polymer composite squirrel cage rotor with high magnetic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polymer composite squirrel cage rotor with high magnetic... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3205399