Gear-Bearing Technology John Vranish - NASA

Gear-Bearing Technology John Vranish Technology Transfer Expo and Conference March 3-6, 2003

Over-View: Gear-Bearings (Components, Devices, Architecture) Explained by describing critical steps in 4- year evolution. Started with NASA search for over-achieving planetary speed reducer. Successful completion pointed towards transferring technology to industry. Weaknesses emerged in satisfying industry needs. Solutions pointed to many new applications and motions beyond planetary transmissions. These new applications pointed to a larger pattern in mechanical engineering. As a pattern began to emerge for so many diverse kinds and sizes of applications, a new, superior mechanical architecture emerged. 2

NASA’s Search for Large Speed Reduction FIRST GEAR-BEARING COMPONENTS AND DEVICE (70:1 SPEED REDUCTION, 1.25 IN. DIA.) 3

Gear-Bearing Roller Component Roller Bearing Radius Gear Pitch Radius Radius to Crowned Top Roller Crowned Tops of Gear Teeth Gear Gear Pitch Diameter 4

Gear-Bearing Roller Stabilization Technique Ring Gear Teeth Ring Roller Sun Gear Teeth Sun Roller Planet Roller Ring Roller Planet Roller Planet Gear Sun Roller Sun Gear Planet Roller Planet Gear Ring Gear 5

Gear-Bearing Interlocking Force Synchronization Tooth #1 Roller #2 Roller #1 Tooth #2 A) Spur Gear on Spur Gear Spur Roller Ring Roller Surface A Ring Gear Tooth Spur Gear Tooth Tooth Pitch Contact Line Ring Roller Surface Spur Gear Tooth C) Section A-A Spur Roller A B) Spur Gear on Ring Gear 6

NASA Search For Large Speed Reduction Continues SINGLE-TOOTH DIFFERENCE GEARBEARING TRANSMISSION (325:1 SPEED REDUCTION, 1.25 IN. DIA.) FIRST USE OF PHASE-TUNED PLANETS 7

Single-Tooth Working Rapid Prototype (185:1) (Uses Phase-Tuned Planets) 8

Single-Tooth Working Rapid Prototype (185:1) (Uses Phase-Tuned Planets) 9

Phase-tuning Provides Unexpected Benefits (WHILE THE NUMBER OF TEETH IN THE GROUND RING AND SUN SHOULD BE DIVISIBLE BY 6) Number of teeth in output ring can be any number-great design flexibility. So multiple planets can be used for strength independent of speed reduction. And targeted super speed reductions are straight forward. 10

Phase-Tuning Provides Targeted Super Speed Reduction (For all Tables, bottom stage has 24 teeth in Sun, 21 teeth in Bottom Planet Half and 66 teeth in Ground Ring) Table 1. Single Tooth Large Speed Reduction Output Ring Planet Top Speed Reduction 1. 65 teeth (-1) 21 teeth (same as Bottom) -243.75:1 2. 67 teeth ( 1) 21 teeth (same as Bottom) 251.25:1 Table 2. Super Large Speed Reduction Output Ring Planet Top Speed Reduction 1. 69 teeth ( 3) 22 teeth ( 1) -1,811.25:1 2. 63 teeth (-3) 20 teeth (-1) 1,653.75:1 11

Phase-Tuning Provides Targeted Super Speed Reduction (continued) (For all Tables, bottom stage has 24 teeth in Sun, 21 teeth in Bottom Planet Half and 66 teeth in Ground Ring) Table 3. Targeted Super Large Speed Reduction (goal of /-500:1) Output Ring Planet Top Speed Reduction 1. 57 teeth (-9) 18 teeth (-3) 498.75:1 (0.25% error) 2. 76 teeth ( 10) 24 teeth ( 3) 498.75:1 (0.25% error) 3. 78 teeth ( 12) 25 teeth ( 4) -511.88:1 (-2.38% error) 12

Successful Completion Pointed Towards Transferring Technology to Industry WEAKNESSES EMERGED IN SATISFYING INDUSTRY NEEDS. 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. 13

Herringbone Gear-Bearing Rollers (Herringbone Planet) Axis of Rotation A. Pictoral Gear Pitch Radius B. Force Locations Gear Teeth Roll Surface Roll Radius Roll Radius Roll Radius Gear Pitch Radius Axis of Rotation 14

Herringbone Gear-Bearing Inner Ring (Herringbone Inner Ring) A. Pictoral View A. Edge View Inner Gear Pitch Radius Inner Gear Pitch Radius Race Radius Race Radius 15

Herringbone Rack A. Pictoral View Gear Pitch Location Race Location B. Edge View 16

Compound Gear-Bearing Components Common Rotation Axis A. Compound Gear-Bearing Roller R2 R2 Upper Roller Radius Upper Gear Pitch Radius Lower Gear Pitch Radius Lower Gear Pitch Radius R1 R1 R2 (Outer Gear Pitch Radius) R1 (Inner Gear Pitch Radius) R2 (Outer Race Radius) (Inner Race) R2 (Inner Gear) R2 R1,R2 Common Center (Outer Gear) R1 R1 (Inner Race Radius) R6R2 Common Center B. Parallel Compound Ring/Rack (Outer Race) R1 C. Series Compound Ring/Rack 17

GearBearing Roller Shaft A. Rotating Shaft Load Path GearBearing Roller Idler GearBearing Roller Sun GearBearing Roller Gear-Bearing Rings Gear-Bearing Devices Gear Bearing Output Ring Compound Gear-Bearing Roller Planet Gear Bearing Ground Ring B. Differential Transmission 18

Differential Transmission (Gears And Bearings) Intermediate Ring Load Path Output Ring Planet Sun Ground Ring Intermediate Ring 19

Rifle True Anti-Backlash Gear-Bearing Planets 20

Rifle True Anti-Backlash Gear-Bearing Planet Friction Locking 21

New Directions In Applications And Motions OUTSTANDING THRUST BEARING PERFORMANCE OF GEARBEARING HELICAL/HERRINGBONE TEETH SUGGESTS MAJOR ROLL IN BEARING APPLICATIONS. GEAR-BEARING ANTI-FRICTION ROTARY SHAFTS. GEAR-BEARING HIGH LOAD WHEEL BEARINGS. GEAR-BEARING APPROACH SEEMS GENERAL ENOUGH TO WORK WELL IN LINEAR SLIDES AND MOTION CONVERSION DEVICES. SIMPLE LINEAR SLIDES (BOTH MODERATE AND LONG STROKE). DIRECTION-REVERSING PAIRS OF LINEAR SLIDES. MOTION CONVERSION DEVICES 22

2 Bearing Load Patterns A. Tapered Bearings B. Ball Bearings C. Spherical Bearings D. Herringbone GearBearings 23

Half Tooth Cross Section View 24

Half Tooth Principle 25

Half Tooth Mesh Sequence 26

Half Tooth Mesh Sequence 27

Half Tooth Mesh Sequence 28

Half Tooth Mesh Sequence 29

Half Tooth Planetary Layout 30

Basic Linear Slides B. Crossed Rollers Slide Slide Housing Gear-Bearing Rollers Slide Housing Slide Slide Housing A. Gear-Bearing Slide Crossed Rollers 31

Long Stroke Linear Slides 1 1 B. Section B-B 2 1 1 1 2 Slide 1 2 2 1 1 Slide 2 2 2 2 Ground A. Section A-A Ground B. End View 32

Direction Reversing Linear Slides Slide I All other rolling members are identical, simple gear-bearing rollers OI OI OI Ground OI Slide OI Ground OI A. Top View I OI & I Idlers same as height Drive Compound Gear-Bearing Roller Ground OI Idler Slide Idler Drive Slide Idler Idler OI Ground Ring is part of ground Ring 33

Ground Rotor Slide Ground Ground Rotor Ground Slide Rotor Linear to Rotary Motion Conversion 34

Gear-Bearing Operational Characteristics BEARING FUNCTION SMOOTHNESS GEAR-BEARINGS ROTATE AND ORBIT BY POSITIVE GEAR ACTION (BEARINGS BY TRACTION DRIVE SUBJECT TO MICRO-CHATTER) GEAR-BEARINGS INHERENTLY MAINTAIN SPACING (BEARINGS REQUIRE A CARRIER, WHICH SLIDES, CATCHES AND ADDS TO CHATTER) GEAR-BEARING GEAR AND BEARING FUNCTIONS MOVE TOGETHER SYNCHRONOUSLY SO MECHANICAL NOISE IS COHERENT AND LESS NOTICEABLE. (BEARINGS MOVE MORE RANDOMLY AND THE NOISE IS INCOHERENT AND MORE NOTICEABLE). 35

Gear-Bearing Operational Characteristics (continued) PRECISION OF MOTION GEAR-BEARING COMPONENTS INTERFACE DIRECTLY TO EACH OTHER AND TEND TO CENTER UP DURING OPERATION. (SEPARATE BEARINGS AND GEARS HAVE INTERMEDIATE MEMBERS, SUCH AS INNER RACES, THAT ADD EXTRA CONSTRAINTS AND CAUSE MICRO-WOBBLE). CONTACT FRICTION LOCATION IN GEAR-BEARINGS ADDS TRACTION DRIVE TO GEAR ACTION TO MINIMIZE TORQUE DRAG. (BEARING LOCATIONS ARE OFFSET FROM GEAR ACTION SO BEARING FRICTION ADDS PARASITIC TORQUE TO GEAR ACTION). 36

Gear-Bearing vs. Present Architecture Gear-bearing devices are constructed using gear-bearing components. (Present architecture uses bearing and gear components and intermediate members.) Gear-bearing components use gear teeth to transfer mechanical force through devices, to perform thrust-bearing functions and to provide bearing separation. (Present architecture uses gear teeth to transfer mechanical force only.) Gear-bearing components use roll surfaces both to perform radial bearing functions and to speed synchronize the multiple contact forces on each component. (Present bearings perform radial and thrust bearing functions. They move asynchronously with respect to gears.) Gear-bearing components interface directly to each other and move together in a mutually synchronous manner. Their contact forces act in rolling friction and resist side and thrust loads in true 4-way bearing action. In this manner, entire gear-bearing devices function using the direct interfaces of various gear-bearing components. (Present architecture uses intermediate members in interfacing device gears and bearings. Bearings, gears, intermediate members move asynchronously.) 37

Contact Information For more information about this technology, please contact Darryl Mitchell with NASA Goddard Space Flight Center’s Technology Transfer Office at: Darryl.R.Mitchell@nasa.gov (301) 286-5169 – phone (301) 286-0301 – fax 38

outstanding thrust bearing performance of gear-bearing helical/herringbone teeth suggests major roll in bearing applications. gear-bearing anti-friction rotary shafts. gear-bearing high load wheel bearings. gear-bearing approach seems general enough to work well in linear slides and motion conversion devices.