WO1999040340A1

WO1999040340A1 - Composite flywheel for angular momentum devices and the like and method of manufacturing same

Info

Publication number: WO1999040340A1
Application number: PCT/US1999/001864
Authority: WO
Inventors: Irving E. Figge, Sr.
Original assignee: Atlantic Research Corp
Current assignee: Atlantic Research Corp
Priority date: 1998-02-04
Filing date: 1999-02-03
Publication date: 1999-08-12
Anticipated expiration: 2000-08-04

Abstract

A flywheel (10) for high angular momentum devices such as gyroscopes and the like, including a drive member (12) having a splined outer portion (16), and a spacer member (20) having a splined inner portion (22) positioned around the drive member (12). The splined inner portion (22) of the spacer member (20) is in cooperating relationship with the splined outer portion (16) of the drive member (12), thereby enabling the drive member (12) to impart a rotational drive force to the spacer member (20). The splined connection between the drive member (12) and the spacer member (20) enables the spacer member (20) to float outwardly from the drive member (12) under centrifugal loading. The flywheel (10) further includes an inertia ring (24) positioned around the spacer member (20) for providing the desired inertia mass for the flywheel (10). The outward movement of the spacer member (20) under centrifugal loading results in its compression against the surrounding inertia ring (24) to reduce radial tension forces in the flywheel (10) when rotated. A method of manufacturing the flywheel (10) is also provided which places the spacer member (20) in a state of compression.

Description

COMPOSITE FLYWHEEL FOR ANGULAR MOMENTUM DEVICES AND THE LIKE AND METHOD OF MANUFACTURING SAME BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an improved flywheel, and more

particularly, to a composite flywheel for high-speed rotational devices, such

as momentum wheels for orbital insertion, gyroscopes and the like, and a

method of manufacturing the flywheel.

Brief Description of the Related Art

Flywheels have been successfully used to provide gyroscopic

stabilization and other functions for various types of devices and vehicles,

such as satellites, space vehicles and the like. Flywheels typically include

a weighted outer portion or ring (inertia mass) which is rotationally driven

or spun at a predetermined rate, thereby generating angular momentum.

The angular momentum generated by the rotating flywheel is

advantageously used in a known manner for stabilization, satellite insertion,

and/or other known applications.

In certain applications, such as in space vehicles and satellites, the

flywheels must be relatively small and lightweight, due to the space and

weight limitations inherent in these types of applications. Thus, flywheels

made from lightweight composite materials have been developed for these

type of applications. On the other hand, a flywheel used in satellite - 2 - applications must be driven at a high rotational speed to generate sufficient

momentum to enable the instrument to provide the stabilization and/or

other function(s) desired.

One problem with known composite flywheels is that the speed at

which the flywheel can be rotated is strictly limited, due to the fact that

centrifugal loading causes radial and tangential forces in the flywheel.

Known composite flywheels fail when operated at high speed generally as

a result of the radial tension. For example, no composite flywheel with an

inertia mass over a certain value has ever been able to pass a Spin Test

established by NASA, wherein the flywheel is driven at 30,000 RPM with

a stop and restart every fifteen minutes for two hours. Failure of this type

of instrumentation, particularly when used for vehicle stabilization, can

result in the loss of expensive equipment and/or serious injury or death to

occupants of the vehicle.

Thus, a need exists for an improved lightweight flywheel to provide

high angular momentum, which enables the systems to operate at a lower

weight and at a higher speed without structurally degrading when compared

to known flywheels.

SUMMARY OF THE INVENTION

A primary of object of the instant invention is to provide an

improved flywheel which can be used for lightweight, high performance,

high inertia flywheel applications. - 3 -

A more specific object of the instant invention is to provide an

improved composite flywheel which can pass the NASA 30,000 RPM Spin

Test (stop/start every fifteen minutes for two hours) with a higher inertial

mass than any other known flywheel that has passed this test.

A further object of the present invention is to provide an improved

flywheel which minimizes or eliminates radial tension forces within the

flywheel, thereby enabling the flywheel to operate at higher speeds and

momentum as compared to known flywheels.

Still another object of the invention is to provide an improved

flywheel which is lightweight, durable and relatively inexpensive to

manufacture.

Another object of the instant invention is to provide an improved

flywheel that can be adapted for use with any rotational energy storing

mechanism.

A further object of the instant invention is to provide an improved

composite flywheel which can reliably be used in gyroscopic stabilization

applications, and, more particularly, in lightweight, high performance, high

inertia satellite orbital insertion applications.

Yet another object of the invention is to provide a method of

manufacturing a flywheel, which method further enhances the operation

and reliability thereof. - 4 -

These and other objects are achieved by the present invention, which

provides a flywheel including a drive member or ring having a splined

outer portion, and a spacer member having a splined inner portion

positioned around the drive member, wherein the splined inner portion of

the spacer member is in a cooperating relationship with the splined outer

portion of the drive member, thereby enabling the drive member to impart

a rotational drive force to the spacer member. The splined connection

between the drive member and the spacer member enables the spacer

member to float outwardly from the drive member under centrifugal

loading resulting from high speed rotation of the flywheel, while still

maintaining a driving connection therewith. The flywheel further includes

an inertia ring positioned around the spacer member for providing the

desired inertia mass for the flywheel. By allowing the spacer material in

the flywheel to float outwardly during rotation into a state of compression

against the inertia ring, radial tension forces in the flywheel are

significantly reduced.

In accordance with another aspect of the instant invention, the spacer

member is provided on the flywheel in a state of compression within the

inertia ring. In accordance with a preferred embodiment of the invention,

the inertia ring is made of metal, such as steel, and a graphite and epoxy

overwrap is provided around the inertia ring. The composite overwrap

uses a room temperature curable resin to allow the stress state in the ring - 5 - and space member to remain unchanged during resin cure of the overwrap,

and to eliminate any potential for delamination between the inertia ring and

the overwrap. The compression forces from the compressed spacer

member are reacted by the inertia ring and overwrap. The spacer member

is preferably made from a Kevlar reinforced nylon material. The spacer

member preferably has a tapered configuration, wherein the upper and

lower surfaces thereof are tapered inwardly toward the inertia ring, in

order to reduce the radial stresses in the portion of the spacer member that

is not restrained by the inertia ring. A plurality of spaced connectors, such

as pins, are used to secure the inertia ring to the spacer member.

In accordance with another aspect of the invention, a method of

manufacturing the flywheel is provided, wherein the method includes:

providing a drive ring having a splined outer portion;

placing a spacer member with a splined inner portion around the drive ring

such that the splined inner portion of the spacer member is in a cooperating

relationship with the splined outer portion of the drive ring; and placing an

inertia ring around said spacer member. Preferably, the step of placing the

inertia ring around the spacer member, includes: shrinking the spacer

member by a cooling process; installing the inertia ring around the spacer

member; and warming the spacer member to ambient temperature. This

process causes the spacer member to be in a state of compression within

the inertia ring when the flywheel is at ambient temperature. - 6 - BRffiF DESCRIPTION OF THE DRAWINGS

Other features, objects and advantages of the subject invention will

become apparent from a study of the following detailed description of the

invention when viewed in light of the accompanying drawings, in which:

Fig. 1 schematically shows a top view of one embodiment of the

flywheel of the present invention;

Fig. 2 shows a sectional view of the flywheel of Fig. 1 along line

2-2 thereof;

Fig. 3 shows a sectional view, similar to Fig. 2, of another

embodiment of the instant invention;

Fig. 4 schematically shows a partial, cut-away view of an exemplary

embodiment of the floating connection within the flywheel, in accordance

with the present invention; and

Fig. 5 shows a view similar to that of Fig. 5, wherein the spacer

member of the flywheel is compressed outwardly due to centrifugal

loading.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, wherein like reference numerals

designate similar parts throughout the various views, the reference numeral

10 is used to generally designate the flywheel of the instant invention. The

flywheel 10 includes an inner or drive member ring 12 constructed to

enable the drive ring 12 to be connected to a driving device (not shown), - 7 - such as a motor. The drive ring 12 may be made of any suitable material

having sufficient strength for the particular application in which the

flywheel 10 is used. The drive ring 12 is preferably made of metal, such

as high strength steel, when the flywheel is intended for high performance,

high inertia applications. In the embodiment of Fig. 1, a plurality of

spaced bolt holes 14 are provided in the drive ring 12 for facilitating

connection of the flywheel 10 to the intended driving device (not shown)

and to hold upper and lower restraining washers (not shown) which

preclude vertical translation of the flywheel relative to the driving device.

In accordance with an important aspect of the instant invention, the

drive ring 12 is provided with a plurality of splines 16 spaced around the

outer portion of the drive ring 12. The splines 16 may have any suitable

shape and may be provided in any suitable configuration around the drive

ring 12. While in the embodiment of Fig.l, the drive ring 12 is shown as

having an open interior 18, the drive ring 12 may be provided without the

open interior 18, depending on the particular manner in which the drive

ring 12 is to be connected to the particular driving device used for a

particular application. It is noted that the instant invention is directed to

the flywheel 10 itself, and not to flywheel driving devices, bearing, or

other aspects of known devices or instrumentation in which the instant

flywheel may be used. Thus, no further details on such other devices are

provided herein, as one skilled in the art can readily implement the instant - 8 - flywheel in any suitable application from the description of the invention

herein.

The flywheel 10 further includes a spacer ring or member 20

positioned around the drive ring 12. The spacer member 20 may be made

of any suitable material, such as a composite material, preferably as

lightweight as possible. In accordance with a preferred embodiment of the

invention, the spacer member 20 is made from a Kevlar reinforced nylon

material, such as the material sold under the trade name Hedlar Z, but any

other suitable, durable and lightweight material could be used.

In accordance with an important aspect of the instant invention, the

spacer member 20 is provided with a plurality of splines 22 around the

inner portion thereof. The splines 22 on the spacer ring 20 and the splines

16 on the drive ring 12 are each shaped relative to one another in a manner

which enables the respective splines 16 and 22 to fit into a cooperating

relationship and to allow the spacer member to float radially without

interference/restraint. This cooperating relationship between the respective

splines 16 and 20, as shown most clearly in Fig. 4, connects the spacer

member 20 to the drive ring 12 in a manner which enables the drive ring

to transfer a driving force to the spacer member. The purpose and

advantage of this splined interconnection between the drive ring 12 and the

spacer member 20 will be explained in more detail hereinafter. The spacer

member 20, may, for example, be milled to create the desired shape. - 9 -

As seen most clearly in Fig. 2, the flywheel 10 further includes an

inertia ring 24 positioned around the spacer member 20, for providing a

desired mass for achieving a desired angular momentum with the flywheel

10 when rotated. The inertia ring 24 may be made of any suitable material

which provides the desired inertia mass, and it is preferably made of a

metal, such as high strength steel. As shown in Fig. 2, the inertia ring 24

is preferably connected to the spacer member 20 with a plurality of spaced

connectors 26, such as tapered pins or the like. For example, three sets

of pins 26 may be used to connect the inertia ring 24 to the spacer member

20, wherein the sets of pins are spaced equally around the diameter of the

inertia ring 24.

The flywheel 10 also preferably includes a wrapping of material

defining an overwrap 28 around the inertia ring 24, to further help secure

the inertia ring 24 to the spacer member 20.

The overwrap 28 is preferably a composite material, and, more

particularly, a graphite fiber/room temperature cure matrix material hoop

wrap, but any suitable material may be used. In accordance with an

important feature of this embodiment of the invention, the overwrap 28

uses a room temperature curable resin system, such as the resin system

sold under the trade name Siloxirane, as the matrix for the overwrap 28.

The advantage achieved by using a room temperature curable resin in the

overwrap will be explained hereinafter. - lo in accordance with an advantageous feature of the instant invention,

the spacer member 20 is preferably provided in a state of compression

within the inertia ring 24 and overwrap 28 when the flywheel 10 is at

ambient temperature. In order to reduce stress in the compressed spacer

member 20, the upper surface 30 and lower surface 32 thereof are

preferably tapered inwardly toward the inertia ring 24, as shown in Figs.

2 and 3. The compression of the spacer member 20 can be achieved, for

example, when manufacturing the instant flywheel 10, by cooling, and

thereby shrinking, the spacer member 20, placing the inertia ring 24

around the shrunken spacer member 20, and then warming the combined

elements to ambient temperature. This process creates a shrink fit for the

spacer member 20 within the inertia ring 24, as a result of a mismatch in

the coefficient of thermal expansion between the material comprising the

spacer member 20 the material comprising the inertia ring 24. The

compression forces from the compressed spacer member 20 are reacted by

the inertia ring 24 and the overwrap 28. Using a room temperature curable

resin in the overwrap 28, enables the residual compression state of the

spacer member 20 to remain unchanged during resin cure and eliminates

any potential for delamination between the inertia ring 24 and the overwrap

28. It is noted that, while providing the spacer member 20 in a

compressed state is advantageous for high inertia applications, this feature

is optional and the invention is not limited thereto. Balancing weight(s) or - 11 - preferably local material removal (not shown) may be provided behind the

overwrap 28 if necessary or desired to balance the flywheel 10.

An alternative embodiment of the instant invention is shown in Fig.

3, wherein the steel inertia ring 24 and graphite/resin overwrap 28 are

replaced by an inertia ring 24' comprised of a preformed wire wound

matrix material. In this alternative embodiment, the spacer member 20

also preferably has a shrink fit within the inertia ring 24' as described

above.

The importance of, and advantages achieved by the splined

connection between the drive ring 12 and the spacer member 20 will now

be described with reference to the exemplary embodiment of the invention

shown in Figs. 4 and 5. As explained above, the drive ring 12 and the

spacer member 20 each include a plurality of splines 16 and 22,

respectively. The splines 16 and 22 fit together in a cooperating or

complementary relationship, and allow a driving force on the drive ring 12

to be transferred to the spacer member 20, and ultimately to the inertia ring

24. This splined connection enables the flywheel 10 to perform its high

speed rotational function when driven by an appropriate driving device.

Fig. 4 shows the flywheel 10 in its non-driven or non-rotating

condition. In this condition, the respective splines 16 and 22 have a

relatively close or tight fit against the spacer member 20 and drive ring 12,

respectively. As shown in Fig. 5, however, the splined connection enables - 12 - the spacer member 20 to compress or float outwardly under centrifugal

loading caused by the rotation of the flywheel 10 when in operation. This

outward compression causes the splined portions of the drive ring 12 and

spacer member 20 to separate from one another by a given amount during

operation of the flywheel. By allowing the spacer member 20 to compress

outwardly by centrifugal loading, radial tension forces are advantageously

eliminated in the spacer member 20 during operation. By eliminating, or

even just reducing the radial tension in this manner, the instant flywheel 10

is able to achieve a higher inertia without structurally degrading, as

compared to known flywheels.

The initial state of inward compression of the spacer member 20 as

a result is its shrink fit, as described above, tends to offset some of the

outward tension forces from the centrifugal loading in the unrestrained

tapered portion of the spacer member, thereby further enhancing the

structural integrity of the instant flywheel 10. Due to the relative depth of

the splines 16 and 22, the splines remain in a cooperating relationship even

when the spacer member 20 floats outwardly, as shown in Fig. 5, thereby

always maintaining a driving connection between the drive ring 12 and the

spacer member 20.

While the splines 16 and 22 on the drive ring 12 and spacer member

20 have been described and shown herein as having a sprocket or

mechanical gear-type configuration, this configuration is only a preferred - 13 - embodiment, and the particular configuration of the splined connection may

vary and be provided in any suitable form which enables the spacer

member to float outwardly from the drive ring 12 while still maintaining

a driving connection therewith. In other words, the instant invention is not

limited to the particular embodiment of the splined connection shown in the

drawings.

The flywheel 10 may be made in any suitable overall size depending

on the particular application in which the flywheel 10 is intended to be

used. The instant flywheel 10 is particularly suited for use in lightweight,

high performance, high inertia applications , such as satellite orbit insertion,

regenerative braking and gyroscopic stabilization applications, but it may

also be used in any suitable application where a flywheel-type energy

storing mechanism is desired.

The particular order in which the respective parts of the flywheel 10

are manufactured and assembled may vary, and the method of the present

invention is not limited to the particular order of the steps as set forth in

the appended method claims, unless otherwise expressly indicated therein.

A flywheel constructed in accordance with the description above,

and having an approximately five inch diameter inertia ring, passed the

NASA 30,000 RPM spin test (stop/start every fifteen minutes for two

hours) and has operated for over two months continuously at 24,000 RPM - 14 - with a higher inertia than has heretofore been possible with any known

flywheel.

While the preferred forms and embodiments of the invention have

been illustrated and described, it will be apparent to those of ordinary skill

in the art that various changes and modifications may be made without

deviating from the inventive concepts and spirit of the invention as set forth

above, and it is intended by the appended claims to define all such changes

and modifications which come within the full scope and true spirit of the

invention.

Claims

- 15 -WHAT IS CLAIMED IS

1. A flywheel, comprising a drive member having a splined outer

portion, a spacer member having a splined inner portion positioned around

said drive member, said splined inner portion of said spacer member being

in a cooperating relationship with said splined outer portion of said drive

member to enable said drive member to impart a rotational drive force to

said spacer member, and an inertia ring around said spacer member,

whereby upon rotation of the flywheel, the splined connection between said

drive member and said spacer member enables said spacer member to

move outwardly relative to said drive member into a state of compression

against said inertia ring.

2. A flywheel as defined in Claim 1, wherein said spacer member is

a composite material.

3. A flywheel as defined in Claim 2, wherein said spacer member is

a fiber reinforced nylon material.

4. A flywheel as defined in Claim 1, wherein said inertia ring is made

of steel.

5. A flywheel as defined in Claim 1, wherein said drive member is

made of steel. - 16 -

6. A flywheel as defined in Claim 1, wherein said spacer member is

tapered inwardly toward said inertia ring along an upper and lower surface

thereof.

7. A flywheel as defined in Claim 1, wherein said spacer member is

in a state of compression.

8. A flywheel as defined in Claim 1, and further comprising an

overwrap ring around said inertia ring.

9. A flywheel as defined in Claim 8, wherein said overwrap ring is a

graphite fiber and resin hoop wrap.

10. A flywheel as defined in Claim 7, and further comprising an

overwrap ring around said inertia ring.

11. A flywheel as defined in Claim 10, wherein said overwrap ring

includes a room temperature cure resin as a matrix for said overwrap ring.

12. A flywheel as defined in Claim 11 , wherein said inertia ring is made

of metal.

13. A flywheel as defined in Claim 1, wherein said inertia ring is

secured to said spacer member by a plurality of connectors.

14. A flywheel as defined in Claim 1, wherein said inertia ring is

constructed of a wire wound matrix material.

15. A flywheel as defined in Claim 14, wherein said spacer member is

in a state of compression. - 17 -

16. A flywheel, comprising a drive member, a spacer member around

said drive member, means for establishing a floating connection between

said drive member and said spacer member to enable said spacer member

to float outwardly from said drive member under centrifugal loading while

still maintaining a driving connection therewith, and an inertia ring around

said spacer member.

17. A flywheel as defined in Claim 16, wherein said inertia ring has a

size which causes said spacer member to be in a state of compression.

18. A flywheel as defined in Claim 17, wherein said spacer member is

tapered inwardly toward said inertia ring on an upper and lower surface

thereof.

19. A flywheel as defined in Claim 18, wherein said inertia ring is made

of metal.

20. A flywheel as defined in Claim 19, further including an overwrap

ring around said inertia ring.

21. A flywheel as defined in Claim 20, wherein said overwrap ring

includes a room temperature cure resin as a matrix for said overwrap ring.

22. A flywheel as defined in Claim 16, wherein said spacer member is

shrink fit within said inertia ring. - 18 -

23. A flywheel as defined in Claim 16, wherein said spacer member has

a higher coefficient of thermal expansion than said inertia ring, thereby

causing said spacer member to be in a state of compression at ambient

temperature.

24. A method of manufacturing a flywheel, comprising the steps of:

providing a drive member having a splined outer portion;

placing a spacer member with a splined inner portion around

said drive member such that said splined inner portion of said spacer

member is in a cooperating relationship with said splined outer portion of

said drive member; and

placing an inertia ring around said spacer member.

25. A method as defmed in Claim 24, wherein said step of placing an

inertia ring around said spacer member, includes the steps of: shrinking

said spacer member by cooling said spacer member; installing said inertia

ring around said spacer member; and warming said spacer member to

ambient temperature, thereby causing said spacer member to be in a state

of compression within said inertia ring when said flywheel is at ambient

temperature.

26. A method as defined in Claim 25, further including the step of

connecting said inertia ring to said spacer member with a plurality of

connectors. - 19 -

27. A method as defined in Claim 25, further including the step of

placing an overwrap of material around said inertia ring.

28. A method as defined in Claim 27, further including the step of using

a room temperature cure resin as a matrix for said overwrap of material.

29. A method as defined in Claim 25, further including using a fiber

reinforced nylon material for said spacer member.