Gear-Bearing Technology

John Vranish

Technology Transfer Expo and Conference

March 3-6, 2003

2

Over-View: Gear-Bearings(Components, Devices, Architecture)

• Explained by describing critical steps in 4- year evolution.

• Started with NASA search for over-achieving planetary speedreducer.

• Successful completion pointed towards transferring technology toindustry.

• Weaknesses emerged in satisfying industry needs.

• Solutions pointed to many new applications and motions beyondplanetary transmissions.

• These new applications pointed to a larger pattern in mechanicalengineering.

• As a pattern began to emerge for so many diverse kinds and sizesof applications, a new, superior mechanical architecture emerged.

3

NASA’s Search for Large Speed Reduction

FIRST GEAR-BEARING COMPONENTS AND DEVICE (70:1 SPEED REDUCTION, 1.25 IN. DIA.)

4

Gear-Bearing Roller Component

Roller Bearing Radius

= Gear Pitch Radius

= Radius to Crowned Top

Roller

CrownedTops of GearTeeth

Gear

Gear PitchDiameter

5

Gear-Bearing Roller Stabilization Technique

Rin

g G

ear

Tee

th

Ring Roller

Sun GearTeeth

Sun Roller

Planet Roller

Planet Roller Sun Roller Planet Roller

PlanetGear

SunGear

PlanetGear

RingRoller

RingGear

6

Gear-Bearing Interlocking ForceSynchronization

Tooth #1

Roller #1

Tooth #2

Roller #2

A

A

Spur Roller Ring RollerSurface

Spur Gear Tooth

Tooth PitchContact Line

A) Spur Gear on Spur Gear

B) Spur Gear on Ring Gear

C) Section A-A

SpurGearTooth

Ring GearTooth

Ring RollerSurface

SpurRoller

7

NASA Search For Large Speed ReductionContinues

SINGLE-TOOTHDIFFERENCE GEAR-

BEARING TRANSMISSION(325:1 SPEED REDUCTION,1.25 IN. DIA.) FIRST USE OFPHASE-TUNED PLANETS

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Single-Tooth Working Rapid Prototype (185:1)(Uses Phase-Tuned Planets)

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Single-Tooth Working Rapid Prototype (185:1)(Uses Phase-Tuned Planets)

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Phase-tuning Provides Unexpected Benefits

(WHILE THE NUMBER OF TEETH IN THE GROUNDRING AND SUN SHOULD BE DIVISIBLE BY 6)

• Number of teeth in output ring can be anynumber-great design flexibility.

• So multiple planets can be used for strengthindependent of speed reduction.

• And targeted super speed reductions arestraight forward.

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(For all Tables, bottom stage has 24 teeth in Sun, 21 teeth in Bottom Planet Halfand 66 teeth in Ground Ring)

Table 1. Single Tooth Large Speed Reduction

+251.25:121 teeth (same as Bottom)2. 67 teeth (+1)

-243.75:121 teeth (same as Bottom)1. 65 teeth (-1)

Speed ReductionPlanet TopOutput Ring

Table 2. Super Large Speed Reduction

+1,653.75:120 teeth (-1)2. 63 teeth (-3)

-1,811.25:122 teeth (+1)1. 69 teeth (+3)

Speed ReductionPlanet TopOutput Ring

Phase-Tuning Provides Targeted Super SpeedReduction

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(For all Tables, bottom stage has 24 teeth in Sun, 21 teeth in Bottom Planet Halfand 66 teeth in Ground Ring)

Table 3. Targeted Super Large Speed Reduction (goal of +/-500:1)

Phase-Tuning Provides Targeted Super SpeedReduction (continued)

-511.88:1 (-2.38% error)25 teeth (+4)3. 78 teeth (+12)

+498.75:1 (0.25% error)24 teeth (+3)2. 76 teeth (+10)

+498.75:1 (0.25% error)18 teeth (-3)1. 57 teeth (-9)

Speed ReductionPlanet TopOutput Ring

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Successful Completion Pointed TowardsTransferring Technology to Industry

WEAKNESSES EMERGED IN SATISFYING INDUSTRYNEEDS.

• Thrust bearing point contact load limitation.

• Not anti-backlash.

• Industry needs both low and high speed reduction.

SOLUTIONS WERE FOUND.• Helical gear teeth forms (including herringbone) give

outstanding thrust bearing performance.• Rifle true anti-backlash (proven out previously by

NASA) applies in this case.• Phase-tuning techniques work to provide low speed

reduction.

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+Gear PitchRadius

Axis of Rotation

Axis of Rotation

+

Gear Teeth

RollSurface

RollRadius

RollRadius

Roll Radius = Gear Pitch Radius

A. Pictoral B. ForceLocations

Herringbone Gear-Bearing Rollers(Herringbone Planet)

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Herringbone Gear-Bearing Inner Ring(Herringbone Inner Ring)

Inner Gear Pitch Radius

Race Radius

A. Pictoral View

A. Edge View

Inner Gear PitchRadius

Race Radius

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Herringbone Rack

Gear Pitch Location

Race Location

A. Pictoral View

B. Edge View

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Compound Gear-Bearing Components

Common Rotation Axis

R2

R2

R1

R1

Upper Roller Radius

Upper Gear Pitch Radius

Lower Gear Pitch Radius

Lower GearPitchRadius

A. Compound Gear-BearingRoller

B. Parallel Compound Ring/Rack C. Series Compound Ring/Rack

R2 (OuterGear PitchRadius) R1 (Inner

Gear PitchRadius)

R1 (InnerRace Radius)

R2 (OuterRace Radius)

R6R2 Common Center

(Inner Race)R2

(Inner Gear)

R2

R1,R2 Common Center

(Outer Gear)R1

(Outer Race)R1

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Gear-Bearing Devices

Gear-BearingRollerShaft

Gear-BearingRoller

Gea

r-B

earin

g R

ings

A. Rotating Shaft

B. Differential Transmission

Gear-BearingRollerIdler

Gear-BearingRollerSun

CompoundGear-BearingRoller Planet

Gear Bearing OutputRing

Gear Bearing GroundRing

Load Path

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Differential Transmission (Gears And Bearings)

Load Path

Output Ring

Ground Ring

Intermediate Ring

Sun

Planet

IntermediateRing

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Rifle True Anti-Backlash Gear-Bearing Planets

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Rifle True Anti-Backlash Gear-Bearing PlanetFriction Locking

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New Directions In Applications And Motions

OUTSTANDING THRUST BEARING PERFORMANCE OF GEAR-BEARING HELICAL/HERRINGBONE TEETH SUGGESTS MAJORROLL IN BEARING APPLICATIONS.

• GEAR-BEARING ANTI-FRICTION ROTARY SHAFTS.

• GEAR-BEARING HIGH LOAD WHEEL BEARINGS.

GEAR-BEARING APPROACH SEEMS GENERAL ENOUGH TOWORK WELL IN LINEAR SLIDES AND MOTION CONVERSIONDEVICES.

• SIMPLE LINEAR SLIDES (BOTH MODERATE AND LONGSTROKE).

• DIRECTION-REVERSING PAIRS OF LINEAR SLIDES.

• MOTION CONVERSION DEVICES

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Bearing Load Patterns

A. Tapered Bearings

B. Ball Bearings

C. Spherical Bearings

D. Herringbone Gear-Bearings

+2

24

Half Tooth Cross Section View

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Half Tooth Principle

26

Half Tooth Mesh Sequence

27

Half Tooth Mesh Sequence

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Half Tooth Mesh Sequence

29

Half Tooth Mesh Sequence

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Half Tooth Planetary Layout

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Basic Linear Slides

Housing Housing

Hou

sing

Slid

e

Slid

eS

lide

Slid

eGear-Bearing Rollers Crossed Rollers

A. Gear-Bearing Slide B. Crossed Rollers Slide

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Long Stroke Linear Slides

Slid

e

Gro

und

A. Section A-A B. Section B-B

B. End ViewGround

Slide

11

11

22

22

12

21

112 2

33

Direction Reversing Linear Slides

Slid

e

Idle

r

Gro

und

Driv

e

OI

Idle

rS

lide

Idle

r

OI

Gro

und

Idle

r

Slid

e

Slid

e

Gro

und

Gro

und

OI

OI

OI

OI

OI

OI

I+I+

DriveCompoundGear-BearingRoller

All other rollingmembers are identical,simple gear-bearingrollers

Ring is part of ground

OI & I Idlers sameas height

Ring

A. Top View

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Linear to Rotary Motion Conversion

Ground

Ground

Rotor

Rotor

Slide

Slide

Ground

Ground

Rot

or

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Gear-Bearing Operational Characteristics

BEARING FUNCTION SMOOTHNESS

• GEAR-BEARINGS ROTATE AND ORBIT BY POSITIVEGEAR ACTION (BEARINGS BY TRACTION DRIVESUBJECT TO MICRO-CHATTER)

• GEAR-BEARINGS INHERENTLY MAINTAIN SPACING(BEARINGS REQUIRE A CARRIER, WHICH SLIDES,CATCHES AND ADDS TO CHATTER)

• GEAR-BEARING GEAR AND BEARING FUNCTIONSMOVE TOGETHER SYNCHRONOUSLY SO MECHANICALNOISE IS COHERENT AND LESS NOTICEABLE.(BEARINGS MOVE MORE RANDOMLY AND THE NOISEIS INCOHERENT AND MORE NOTICEABLE).

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Gear-Bearing Operational Characteristics(continued)

PRECISION OF MOTION

• GEAR-BEARING COMPONENTS INTERFACE DIRECTLY TOEACH OTHER AND TEND TO CENTER UP DURINGOPERATION. (SEPARATE BEARINGS AND GEARS HAVEINTERMEDIATE MEMBERS, SUCH AS INNER RACES, THATADD EXTRA CONSTRAINTS AND CAUSE MICRO-WOBBLE).

• CONTACT FRICTION LOCATION IN GEAR-BEARINGS ADDSTRACTION DRIVE TO GEAR ACTION TO MINIMIZE TORQUEDRAG. (BEARING LOCATIONS ARE OFFSET FROM GEARACTION SO BEARING FRICTION ADDS PARASITIC TORQUE TOGEAR ACTION).

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Gear-Bearing vs. Present Architecture

• Gear-bearing devices are constructed using gear-bearingcomponents. (Present architecture uses bearing and gearcomponents and intermediate members.)

• Gear-bearing components use gear teeth to transfer mechanicalforce through devices, to perform thrust-bearing functions and toprovide bearing separation. (Present architecture uses gear teethto transfer mechanical force only.)

• Gear-bearing components use roll surfaces both to perform radialbearing functions and to speed synchronize the multiple contactforces on each component. (Present bearings perform radial andthrust bearing functions. They move asynchronously with respectto gears.)

• Gear-bearing components interface directly to each other andmove together in a mutually synchronous manner. Their contactforces act in rolling friction and resist side and thrust loads in true4-way bearing action. In this manner, entire gear-bearing devicesfunction using the direct interfaces of various gear-bearingcomponents. (Present architecture uses intermediate members ininterfacing device gears and bearings. Bearings, gears,intermediate members move asynchronously.)

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Contact Information

For more information about this technology,please contact Darryl Mitchell with NASAGoddard Space Flight Center’s TechnologyTransfer Office at:

Darryl.R.Mitchell@nasa.gov

(301) 286-5169 – phone

(301) 286-0301 – fax