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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
8
Single-Tooth Working Rapid Prototype (185:1)(Uses Phase-Tuned Planets)
9
Single-Tooth Working Rapid Prototype (185:1)(Uses Phase-Tuned Planets)
10
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.
11
(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
12
(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
13
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.
14
+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)
15
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
16
Herringbone Rack
Gear Pitch Location
Race Location
A. Pictoral View
B. Edge View
17
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
18
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
19
Differential Transmission (Gears And Bearings)
Load Path
Output Ring
Ground Ring
Intermediate Ring
Sun
Planet
IntermediateRing
20
Rifle True Anti-Backlash Gear-Bearing Planets
21
Rifle True Anti-Backlash Gear-Bearing PlanetFriction Locking
22
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
23
Bearing Load Patterns
A. Tapered Bearings
B. Ball Bearings
C. Spherical Bearings
D. Herringbone Gear-Bearings
+2
24
Half Tooth Cross Section View
25
Half Tooth Principle
26
Half Tooth Mesh Sequence
27
Half Tooth Mesh Sequence
28
Half Tooth Mesh Sequence
29
Half Tooth Mesh Sequence
30
Half Tooth Planetary Layout
31
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
32
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
34
Linear to Rotary Motion Conversion
Ground
Ground
Rotor
Rotor
Slide
Slide
Ground
Ground
Rot
or
35
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).
36
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).
37
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.)
38
Contact Information
For more information about this technology,please contact Darryl Mitchell with NASAGoddard Space Flight Center’s TechnologyTransfer Office at:
(301) 286-5169 – phone
(301) 286-0301 – fax