Title of Invention

STRUCTURE AND METHOD OF ROTOR ASSEMBLY WITHOUT THE HUB

Abstract A structure and method of assembling a rotor assembly is provided, without the use of a rotor steel hub. The method comprises forming first, second and third lamination stacks by stacking individual rotor laminations together. The first, second and third lamination stacks are cast to lock the individual rotor laminations together. The rotor laminations in the first, second and third lamination stacks have a generally ring-like shape with a variable inner diameter and a substantially common outer diameter. The rotor laminations in the first, second and third lamination stacks have substantially the same outer diameter, whereas the rotor laminations in the second lamination stack have a substantially larger inner diameter than the first and third rotor laminations. The elimination of the hub results in reducing total cost and manufacturing cycle time, and in improved features, performance and efficiency of the rotor assembly.
Full Text 1
GP-302490
STRUCTURE AND METHOD OF ROTOR ASSEMBLY WITHOUT THE HUB
TECHNICAL FIELD
[0001] This invention relates to a structure and method of assembling a rotor
assembly, without the use of a rotor steel hub.
BACKGROUND OF THE INVENTION
[0002] Conventional electric motors generally comprise of a cylindrical stator and
a rotor assembly located within the stator. Typically, the rotor assembly is constructed
with the aid of a heavy steel hub. The hub is used to ensure that the rotor laminations are
connected to external structures and support the structure of the rotor assembly. The use
of a hub requires special machining for locking rotor components or tabs to the hub. In
the use of a hub to assemble the rotor assembly, the rotor components or tabs must be
perfectly aligned to complete the assembly process.
[0003] In order for the hub to slide over the rotor lamination stack, a gap must be
created. The hub is ordinarily contracted with the use of liquid nitrogen at -300° F while
the rotor laminations are expanded with the use of an oven at 400° F. As the temperatures
normalize, the gap dissipates and a "shrink-fit" between the hub and rotor laminations
results.
[0004] Other typical rotor assemblies include a supporting rotor shaft extending
through a central hole in the stack of rotor laminations. The rotor shaft may also be
welded onto either end of the stack of rotor laminations.
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SUMMARY OF THE INVENTION
[0005] The present invention eliminates the use of a hub in assembling the rotor
assembly. There is no supporting rotor shaft extending through the center of the stack of
rotor laminations or attached at the ends of the stack of rotor laminations.
[0006] A structure and method of assembling a rotor assembly is provided. The
first step comprises forming a first lamination stack by stacking individual first rotor
laminations. The first lamination stack has a first end and a second end. The second step
comprises stacking individual second rotor laminations onto the second end of the first
lamination stack, thereby creating a second lamination stack. The second lamination
stack has a first end and a second end. The third step comprises stacking a set of third
rotor laminations onto the second end of the second lamination stack thereby creating a
third lamination stack. The third lamination stack has a first end and a second end.
[0007] In another aspect of the invention, the first, second and third lamination
stacks are cast to lock the first, second and third rotor laminations together. The first, second and third rotor laminations have a generally ring-like shape with a variable inner diameter and a substantially common outer diameter. The first, second and third rotor laminations have substantially the same outer diameter, whereas the second rotor laminations have a substantially larger inner diameter than the first and third rotor laminations.
[0008] The elimination of the hub results in the elimination of the use of liquid
nitrogen at -300° F and oven at 400° F in the "shrink-fit" process described above. Fewer parts are needed with the method of this invention than are typically required, resulting in less inventory problems. The cost of assembling the rotor is reduced as is the time required to manufacture and assemble the rotor.
[0009] The above method also leads to improved rotor heat transfer for improved
rotor oil cooling. As a result of the elimination of the rotor hub, the oil contained within the rotor has better contact with the rotor laminations, leading to better heat transfer. A cooler motor draws less electric current to operate, thereby reducing electric power consumption,The improved method also leads to better concentricity between the outer
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and inner diameters of the rotor. The gap between the outer diameter of the rotor and
stator inner diameter will be more uniform and consistent since the flange bearing
journals on both ends are more concentric.
[0010] The above features and other features and advantages of the present
invention are readily apparent from the following detailed description of the best modes
for carrying out the invention when taken in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIGURE 1 is a fragmentary schematic perspective view of the rotor
assembly;
[0012] FIGURE 2 is a fragmentary schematic cross sectional view of the rotor
assembly; and
[0013] FIGURE 3 is a schematic perspective view of the bolt used in the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] In the embodiment described below, the rotor assembly is used in an
electric motor in a hybrid transmission for a vehicle. However the method and structure
described below is suitable for use with rotors for induction machines, permanent magnet
and switch reluctance machines as well as other suitable machines.
[0015] Referring to Figure 1, a perspective view of part of a rotor assembly 10 is
illustrated. Figure 2 is a schematic cross sectional view of part of the rotor assembly 10. The rotor assembly comprises a first lamination stack 20, second lamination stack 30 and a third lamination stack 40. The first lamination stack 20 is made up of individual first rotor laminations 22. The first lamination stack 20 has a first end 24 and a second end 26. The rotor assembly 10 also comprises a second lamination stack 30, attached to the second end 26 of the first lamination stack 20. The second lamination stack 30 is made up of individual second rotor laminations 32. The second lamination stack 30 has a first end
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34 and a second end 36. The rotor assembly 10 also comprises a third lamination stack
40, attached to the second end 36 of the second lamination stack 30. The third lamination
stack 40 is made up of individual third rotor laminations 42. The third lamination stack
40 has a first end 44 and a second end 46. The first lamination stack 20 and the third
lamination stack 40 are substantially identical in size, see discussion below.
[0016] The first, second and third rotor laminations 22, 32 and 42 respectively are
generally circular disks which are made of flat sheets of silicone steel. The sheets, which may be made of other suitable materials, are fitted into a punching die (not shown) which punches holes into the sheet resulting in a generally ring-like shape. Other non-circular shapes that are suitable for use in various electric machine rotor assemblies may also be employed.
[0017] As shown in Figure 1, the first, second and third rotor laminations 22, 32 and 42 have an opening with center 50, an inner circumference 52 and an outer circumference 54. The distance between two points on the outer circumference 54, going through the center 50 of the opening represents the outer diameter OD of each rotor lamination, as shown in Figure 1. The distance between two points on the inner circumference 52, going through the center 50 of the opening represents the inner diameter ID of each rotor lamination, as shown in Figure 1. Each of the first, second and third rotor laminations 22, 32, 42 have annulus regions A1, A2 and A3, respectively, between their respective inner and outer circumferences 52 and 54.
[0018] In the embodiment shown, the first, second and third rotor laminations 22,
32 and 42 are stacked in an axial direction. The first lamination stack 20 has an axial length L1. The second lamination stack 30 has an axial length L2. The third lamination stack 40 has an axial length L3. There are approximately 25 first rotor laminations 22 in the first lamination stack 20. There are approximately 220 second rotor laminations 32 in the second lamination stack 30. There are approximately 25 third rotor laminations 42 in the third lamination stack 40. Thus, in the preferred embodiment, the second lamination stack 30 has an axial length L2 greater than either of the first and third lamination stacks 20 and 40, i.e. the second lamination stack 30 contains a greater number of individual
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rotor laminations than either of the first and third lamination stacks 20 and 40 or the laminations of the combined laminations of the first and third lamination stacks 20 and 40. Existing automated lamination feeding and stacking machines can be utilized for this assembly process.
[0019] In terms of the sizes of the individual rotor laminations, the first, second
and third rotor laminations 22, 32 and 42 have substantially the same outer diameter OD. However the first and third rotor laminations 20 and 40 have substantially smaller inner diameters ID than the second rotor laminations 30, as shown in Figures 1 and 2, to allow for the placement of bolt holes 60. Thus the annulus region A1 and A3 is larger for the first and third rotor laminations 20 and 40 than the annulus region A2 of the second rotor lamination 30.
[0020] As shown in Figure 1, slots 62 extend along the periphery of the outer
circumference 54 of the first, second and third rotor laminations 22, 32 and 42. The first, second and third lamination stacks 20, 30 and 40 are cast together by first being placed in a die cast mold fixture (not shown). The first, second and third lamination stacks 20, 30 and 40 are molded by applying pressure to lock the first, second and third lamination stacks 20, 30 and 40 together.
[0021] Molten aluminum or other suitable material is injected into the slots 62.
The molten aluminum flows through the slots 62 from the first end 24 of the first lamination stack 20 to the second end 46 of the third lamination stack 40. A means of pressure such as hydraulic back pressure is applied against the molten metal forcing the molten metal into the slots 62 to lock the first, second and third rotor laminations 22, 32 and 42 together in a unitary configuration, thereby avoiding air gaps, porosity and bubbles. For example, the first, second and third lamination stacks 20, 30 and 40 may be compressed together in a die-casting machine so as to lock the first, second and third rotor laminations 22, 32 and 42 together. The molten aluminum solidifies to create a first end ring 64 at the first end 24 of the first lamination stack 20 and a second end ring 66 at the second end 46 of the third lamination stack 40, see Figure 2. The aluminum or other
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suitable material first and second end rings 64 and 66 serve to enhance the conductivity of the rotor assembly 10.
[0022] As shown in Figures 1 and 2, bolt holes 60 extend along the periphery of
the inner circumference 52 of the first and third rotor laminations 22 and 42. The bolt holes 60 are configured to receive a corresponding bolt 68.
[0023] Figure 3 is a schematic perspective view of a bolt 68. The head of each
bolt 68 has a flat side 67 that may be used to wedge and lock the bolt 68 in the first and third lamination stacks 20 and 40. Each bolt 68 has serrations 69 that prevent the bolt 68 from rotating and interact with complementary slots on the inside of each bolt hole 60. The flat side 67 of the head of the bolt 68 and the serrations 69 provide anti-rotation when the first and second flange 74 and 76 (see discussion below) is assembled and the nut 78 is tightened. There are twelve bolt holes 60 in the preferred embodiment, however any number of bolt holes may be used. A representative first bolt 70 and representative second bolt 72 is shown in Figure 2, attached onto the first lamination stack 20 and the third lamination stack 40, respectively.
[0024] A first flange 74 is attached onto the first end 24 of the first lamination
stack 20, using the first bolt 70 for orientation. The first bolt 70 goes through a hole in the first flange 74. A second flange 76 is attached onto the second end 46 of the third lamination stack 40, using the second bolt 72 for orientation. The second bolt 72 goes through a hole in the second flange 76. As stated above, the preferred embodiment describes a rotor assembly 10 used in an electric motor (not shown) in a hybrid transmission. The first and second flanges 74 and 76 are mechanical devices that provide a means of attachment for the first, second and third lamination stacks 20, 30 and 40 to the gears and/or other parts of the electric motor in the transmission. The first and second flanges 74 and 76 help transmit power to the mechanical components of the electric motor. A set of nuts 78 are placed over the edges of the first and second bolts 70 and 72 for secure attachment of flange to rotor assembly.
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[0025] Alternatively, a single flange with multiple holes to mate with respective
first and second bolts 70 or 72 may be used. Any number of multiple flanges may also be used. The flange may be constructed of steel or other suitable materials. The physical structure or configuration of the flange may be varied depending on the layout and design of the components to be attached to the rotor laminations 22, 32 and 42 through the flange. Method
[0026] A method for assembling the rotor assembly 10 described above is
provided. The first step comprises forming a first lamination stack 20 by stacking
individual first rotor laminations 22. The first lamination stack 20 has a first end 24 and a
second end 26. The second step comprises stacking individual second rotor laminations
32 onto the second end 26 of the first lamination stack 20 thereby creating a second
lamination stack 30. The second lamination stack 30 has a first end 34 and a second end
36. The third step comprises stacking a set of third rotor laminations 42 onto the second
end 36 of the second lamination stack 30 thereby creating a third lamination stack 40.
The third lamination stack 40 has a first end 44 and a second end 46.
[0027] The first, second and third lamination stacks 20, 30 and 40 may be cast
together in a die cast mold fixture and molded to lock the first, second and third rotor laminations 22, 32 and 42 together. A dowel pin or a guide bar (not shown) may be used to ensure the proper alignment of the first, second and third lamination stacks 20, 30 and 40. The guide bar may be used to align the stacking of the first, second and third lamination stacks in the die cast mold fixture prior to molding. The dowel pin or guide bar may be inserted into a respective one or more slots 62 of the rotor lamination 42 and extend axially through the slot to the first end 24 of the first lamination stack 20 or from the first end 24 to the second end 46.
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[0028] A first bolt 70 may be attached onto the first lamination stack 20 as well as
a second bolt 72 onto the third lamination stack 40. A first flange 74 may be attached
onto the first end 24 of the first lamination stack 20, using the first bolt 70 for orientation;
and a second flange 76 may be attached onto the second end 46 of the third lamination
stack 40, using the second bolt 72 for orientation.
Other Steps
[0029] A further step may comprise machining the outer circumference 54 of the
first second and third rotor laminations 22, 32 and 42. Machining involves grinding the
outer circumference 54 for smoothness and precision of dimensions. This process may
be done at the final rotor assembly, which involves assembling both flanges.
[0030] A further step may involve fine-tuning a speed sensor wheel 80. Certain
rotor assemblies may contain a speed sensor wheel 80, as shown in Figure 2. The speed
sensor wheel 80 may be an integral part of the flange structure or it may be mounted
separately by welding, using bolts or other means. If mounted on the structure, the speed
sensor wheel 80 must be attached securely so it does not vibrate.
[0031] Finally, a next step may be final balancing of the rotor assembly 10, which
involves removing and adding extremely small amounts of weight at either end of the
rotor assembly 10. This serves to balance the weight of the rotor assembly 10 from one
end to the other, leading to reduced vibration and noise.
[0032] The thickness of the hub used typically in constructing a rotor restricts the
width A2 of rotor laminations to what can be fitted within the hub. Eliminating the hub
allows for the cross-sectional area of the rotor laminations to be increased. This allows
for a greater electromagnetic flux path and increased efficiency of the motor.
Furthermore, the electric motor performance and efficiency is improved as a result of the
elimination of the contact pressure applied by the hub on the rotor laminations.
[0033] While the best modes for carrying out the invention have been described
in detail, those familiar with the art to which this invention relates will recognize various
alternative designs and embodiments for practicing the invention within the scope of the
appended claims.
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CLAIMS
1. A method of rotor assembly comprising:
stacking first rotor laminations sufficiently to create a first lamination stack, wherein said first lamination stack has a first end and a second end;
stacking second rotor laminations sufficiently onto said second end of said first lamination stack thereby creating a second lamination stack, wherein said second lamination stack has a first end and a second end;
stacking third rotor laminations sufficiently onto said second end of said second lamination stack thereby creating a third lamination stack, wherein said third lamination stack has a first end and a second end;
casting said first, second and third lamination stacks to lock said first, second and third rotor laminations together;
wherein said first, second and third rotor laminations have a shape with a variable inner diameter and a substantially common outer diameter;
wherein said first, second and third rotor laminations have substantially the same outer diameter; and
wherein said second rotor laminations have a larger inner diameter than said first and third rotor laminations.
2. The method of claim 1, wherein said shape of said first, second and
third rotor laminations is a ring shape, having an outer and inner circumference.
3. The method of claim 2, wherein slots extend along periphery of
outer circumference of said first, second and third rotor laminations.
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4. The method of claim 3, wherein said casting of said first, second
and third lamination stacks comprises:
placing said first, second and third lamination stacks in a die cast mold fixture:
molding said first, second and third lamination stacks by applying pressure to lock said first, second and third lamination stacks together;
injecting molten metal into said slots extending along periphery of outer circumference of said first, second and third rotor laminations, wherein said molten metal is injected from said first end of said first lamination stack to said second end of said third lamination stack; and
applying hydraulic back pressure against said molten metal to avoid air gaps, bubbles or porosity inside said first, second and third lamination stacks.
5. The method of claim 4,
wherein said molten metal through said die cast mold fixture solidifies at said first end of said first lamination stack to create a first metal end ring; and
wherein said molten material through said slots solidifies at said second end of said third lamination stack to create a second metal end ring on the opposite end of said rotor assembly.
6. The method of claim 1, further comprising the steps of:
attaching a first bolt onto said first lamination stack;
attaching a second bolt onto said third lamination stack;
attaching a first flange onto said first end of said first lamination stack, using said first bolt for orientation; and
attaching a second flange onto said second end of said third lamination stack, using, said second bolt for orientation.
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7. The method of claim 1, wherein at least one guide bar is used to
align said stacking of said first, second and third lamination stacks in said die cast mold
fixture prior to molding.
8. The method of claim 1, wherein said first and said third rotor
laminations number approximately 25.
9. The method of claim 1, wherein said second rotor laminations
number approximately 220.
10. A rotor assembly comprising:
a first lamination stack comprised of first rotor laminations, wherein said first lamination stack has a first end and a second end;
a second lamination stack attached onto said second end of said first lamination stack, wherein said second lamination stack is comprised of second rotor laminations, wherein said second lamination stack has a first end and a second end;
wherein said first and second lamination stacks are cast together;
wherein said first and second rotor laminations have a ring shape with an inner diameter and an outer diameter;
wherein said first and second rotor laminations have substantially the same outer diameter; and
wherein said second rotor lamination has a substantially larger inner diameter than said first rotor laminations.
11. The rotor assembly of claim 10, further comprising:
a third lamination stack attached onto said second end of said second lamination stack, wherein said third lamination stack is comprised of third rotor laminations, wherein said third lamination stack has a first end and a second end;
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wherein said third lamination stack is cast together with said first and second lamination stacks;
wherein said third rotor laminations have a ring shape with an inner diameter and an outer diameter;
wherein said third rotor laminations have substantially the same outer diameter as the first and second rotor laminations; and
wherein said second rotor lamination has a substantially larger inner diameter than either of said first and third rotor laminations.
12. The rotor assembly of claim 11, wherein slots extend along
periphery of outer circumference of said ring shape of said first, second and third rotor
laminations.
13. A method of rotor assembly without a hub comprising:
stacking at least one plurality of annular laminations to form a first
lamination stack having an inner diameter of substantially one predetermined size; and
stacking another plurality of annular laminations onto said first lamination stack to form a second lamination stack having an inner diameter of substantially another predetermined size to facilitate the attachment of the rotor assembly without a hub.
14. The method of claim 13 including stacking another plurality of
annular laminations onto said second lamination stack to form a third lamination stack
having an inner diameter of said one predetermined size.
15. The method of claim 14 including placing said first and second and
third lamination stacks into a casting mold; and compressing said lamination stacks
sufficiently to lock all laminations together and provide a solid core assembly.
A structure and method of assembling a rotor assembly is provided, without the use of a rotor steel hub. The method comprises forming first, second and third lamination stacks by stacking individual rotor laminations together. The first, second and third lamination stacks are cast to lock the individual rotor laminations together. The rotor laminations in the first, second and third lamination stacks have a generally ring-like shape with a variable inner diameter and a substantially common outer diameter. The rotor laminations in the first, second and third lamination stacks have substantially the same outer diameter, whereas the rotor laminations in the second lamination stack have a substantially larger inner diameter than the first and third rotor laminations. The elimination of the hub results in reducing total cost and manufacturing cycle time, and in improved features, performance and efficiency of the rotor assembly.

Documents:

00945-kol-2006-abstract.pdf

00945-kol-2006-claims.pdf

00945-kol-2006-correspondence others-1.1.pdf

00945-kol-2006-correspondence others.pdf

00945-kol-2006-description(complete).pdf

00945-kol-2006-drawings.pdf

00945-kol-2006-form-1.pdf

00945-kol-2006-form-2.pdf

00945-kol-2006-form-26.pdf

00945-kol-2006-form-3.pdf

00945-kol-2006-form-5.pdf

00945-kol-2006-priority document-1.1.pdf

00945-kol-2006-priority document.pdf

945-KOL-2006-(20-11-2012)-CORRESPONDENCE.pdf

945-KOL-2006-(20-11-2012)-FORM 3.pdf

945-KOL-2006-(26-03-2013)-ABSTRACT.pdf

945-KOL-2006-(26-03-2013)-CLAIMS.pdf

945-KOL-2006-(26-03-2013)-CORRESPONDENCE.pdf

945-KOL-2006-(26-03-2013)-DESCRIPTION (COMPLETE).pdf

945-KOL-2006-(26-03-2013)-DRAWINGS.pdf

945-KOL-2006-(26-03-2013)-FORM 1.pdf

945-KOL-2006-(26-03-2013)-FORM 13.pdf

945-KOL-2006-(26-03-2013)-FORM 2.pdf

945-KOL-2006-(26-03-2013)-FORM 3.pdf

945-KOL-2006-(26-03-2013)-OTHERS.pdf

945-KOL-2006-(26-03-2013)-PETITION UNDER RULE 137.pdf

945-KOL-2006-ASSIGNMENT 1.1.pdf

945-KOL-2006-ASSIGNMENT.pdf

945-KOL-2006-CANCELLED PAGES.pdf

945-KOL-2006-CORRESPONDENCE 1.1.pdf

945-KOL-2006-CORRESPONDENCE-1.2.pdf

945-KOL-2006-CORRESPONDENCE.pdf

945-KOL-2006-EXAMINATION REPORT.pdf

945-kol-2006-form 18.pdf

945-KOL-2006-FORM 26.pdf

945-KOL-2006-FORM 6 -1.1.pdf

945-KOL-2006-FORM 6.pdf

945-KOL-2006-GPA.pdf

945-KOL-2006-GRANTED-ABSTRACT.pdf

945-KOL-2006-GRANTED-CLAIMS.pdf

945-KOL-2006-GRANTED-DESCRIPTION (COMPLETE).pdf

945-KOL-2006-GRANTED-DRAWINGS.pdf

945-KOL-2006-GRANTED-FORM 1.pdf

945-KOL-2006-GRANTED-FORM 2.pdf

945-KOL-2006-GRANTED-FORM 3.pdf

945-KOL-2006-GRANTED-FORM 5.pdf

945-KOL-2006-GRANTED-SPECIFICATION-COMPLETE.pdf

945-KOL-2006-OTHERS.pdf

945-KOL-2006-PA.pdf

945-KOL-2006-REPLY TO EXAMINATION REPORT.pdf

945-KOL-2006-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf

abstract-00945-kol-2006.jpg


Patent Number 258059
Indian Patent Application Number 945/KOL/2006
PG Journal Number 49/2013
Publication Date 06-Dec-2013
Grant Date 29-Nov-2013
Date of Filing 19-Sep-2006
Name of Patentee GM GLOBAL TECHNOLOGY OPERATIONS INC
Applicant Address 300 GM RENAISSANCE CENTER DETROIT, MICHIGAN 48265-3000
Inventors:
# Inventor's Name Inventor's Address
1 MOHSEN M. ERFANFAR 1788 SUMMER LAKES CT., CARMEL, INDIANA 46032
PCT International Classification Number H02K1/00; H02K1/06
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 11/263,177 2005-10-31 U.S.A.