14 Rolling element bearings for rotary motion
Lecture 14 Rolling Element Bearings for Rotary Motion
14-1
Outline • General Characteristics • Bearing Types • Thermocentric Design
14-2
Taper Roller Bearing
Deep Groove Ball Bearing
Cylinder Roller Bearing
Source: http://www.allproducts.com/prc/lyc/showroom1.html
14-3
Bearings Components
Seal
Rolling elements Outer ring
Inner ring Cage
Seal
14-4
Rolling-Element Bearings • Pros
• Cons
¾ Low starting and running friction ¾ Easy lubrication ¾ Small axial space ¾ Radial and axial loads ¾ Predictable failure ¾ Standards (ABEC) ¾ Can be preloaded ¾ Easy mounting
¾ Greater diametrical space ¾ More expensive ¾ Noisy ¾ Finite life ¾ Vulnerable to dirt ¾ Limited shock loading
Annular Bearing Engineers Committee (ABEC)
14-5
Ball Bearings • Ball Bearings ¾ Point contact; support radial and axial loads
• Angular Contact Bearings ¾ Designed for axial loading; used in pairs
• Self-Aligning Bearings • Double Row Bearings ¾ Support higher loads
• Thrust Bearings ¾ Designed for pure axial loading 14-6
Ball Bearing Configurations for Rotary Motion Bearings
14-7
Roller Bearings • Straight ¾Supports high radial loads; slower speed ratings
• Tapered ¾High radial and axial load ratings; used in pairs
• Spherical ¾Allows for misalignment
• Needle ¾Thrust and radial types; typically no inner race 14-8
Roller Bearing Configurations for Rotary Motion Bearings
14-9
Terminology • Inner race • Outer race • Inner and diameters • Width • Options
outer
¾ Open, shielded, sealed ¾ grooves, flanges ¾ wide inner race 14-10
Ball Bearings • Important dimensions
14-11
Tapered Roller Bearings
14-12
Bearing Specifications • Types, series, options • Dimensions • Load Ratings ¾Static (C0): maximum (pre-damage) load ¾Dynamic (C): the load that will give a life of 106 revolutions ¾Axial/Radial
• Speed Rating 14-13
Example
http://www.zklbearings.com/catalog.html
14-14
Example
14-15
Rotary Motion Rolling Element Bearings • The rotary motion rolling element bearings can be made more accurate than linear motion rolling. • The design and production of a rolling element bearing requires careful analysis, materials selection, manufacturing quality control, and testing.
14-16
Linear Rolling Element Bearing Configurations
14-17
Rolling Bearing
http://www.fag.com
14-18
General Characteristics of Rolling Bearings
14-19
Speed and Acceleration Limits • Centrifugal force expands the outer race and increases the contact stress between the balls and the outer race.. • Viscous shear in the lubricant and imperfect rolling contact cause the entire bearing to thermally expand. ¾ Hertzian deformation means that the bearing is making contact at a range of different radii!
14-20
http://pergatory.mit.edu/2.007/lectures/final/Topic_09_Structural_Interfaces.pdf
14-21
http://pergatory.mit.edu/2.007/lectures/final/Topic_09_Structural_Interfaces.pdf
14-22
Hertz Contact Stress
14-23
Speed and Acceleration Limits • The outer race usually is attached to a bigger heat sink so it tends to expand less. ¾A back-to-back bearing configuration is used to maintain stability.
14-24
Speed and Acceleration Limits • When the line of contact is not aligned with the angular acceleration vector (e.g., angular contact bearings): ¾At high speeds, gyroscopic forces cause the ball to spin. ¾At high speeds, a cooling and lubricating oil mist is often required: &Oil mist requires clean, dry (
14-1
Outline • General Characteristics • Bearing Types • Thermocentric Design
14-2
Taper Roller Bearing
Deep Groove Ball Bearing
Cylinder Roller Bearing
Source: http://www.allproducts.com/prc/lyc/showroom1.html
14-3
Bearings Components
Seal
Rolling elements Outer ring
Inner ring Cage
Seal
14-4
Rolling-Element Bearings • Pros
• Cons
¾ Low starting and running friction ¾ Easy lubrication ¾ Small axial space ¾ Radial and axial loads ¾ Predictable failure ¾ Standards (ABEC) ¾ Can be preloaded ¾ Easy mounting
¾ Greater diametrical space ¾ More expensive ¾ Noisy ¾ Finite life ¾ Vulnerable to dirt ¾ Limited shock loading
Annular Bearing Engineers Committee (ABEC)
14-5
Ball Bearings • Ball Bearings ¾ Point contact; support radial and axial loads
• Angular Contact Bearings ¾ Designed for axial loading; used in pairs
• Self-Aligning Bearings • Double Row Bearings ¾ Support higher loads
• Thrust Bearings ¾ Designed for pure axial loading 14-6
Ball Bearing Configurations for Rotary Motion Bearings
14-7
Roller Bearings • Straight ¾Supports high radial loads; slower speed ratings
• Tapered ¾High radial and axial load ratings; used in pairs
• Spherical ¾Allows for misalignment
• Needle ¾Thrust and radial types; typically no inner race 14-8
Roller Bearing Configurations for Rotary Motion Bearings
14-9
Terminology • Inner race • Outer race • Inner and diameters • Width • Options
outer
¾ Open, shielded, sealed ¾ grooves, flanges ¾ wide inner race 14-10
Ball Bearings • Important dimensions
14-11
Tapered Roller Bearings
14-12
Bearing Specifications • Types, series, options • Dimensions • Load Ratings ¾Static (C0): maximum (pre-damage) load ¾Dynamic (C): the load that will give a life of 106 revolutions ¾Axial/Radial
• Speed Rating 14-13
Example
http://www.zklbearings.com/catalog.html
14-14
Example
14-15
Rotary Motion Rolling Element Bearings • The rotary motion rolling element bearings can be made more accurate than linear motion rolling. • The design and production of a rolling element bearing requires careful analysis, materials selection, manufacturing quality control, and testing.
14-16
Linear Rolling Element Bearing Configurations
14-17
Rolling Bearing
http://www.fag.com
14-18
General Characteristics of Rolling Bearings
14-19
Speed and Acceleration Limits • Centrifugal force expands the outer race and increases the contact stress between the balls and the outer race.. • Viscous shear in the lubricant and imperfect rolling contact cause the entire bearing to thermally expand. ¾ Hertzian deformation means that the bearing is making contact at a range of different radii!
14-20
http://pergatory.mit.edu/2.007/lectures/final/Topic_09_Structural_Interfaces.pdf
14-21
http://pergatory.mit.edu/2.007/lectures/final/Topic_09_Structural_Interfaces.pdf
14-22
Hertz Contact Stress
14-23
Speed and Acceleration Limits • The outer race usually is attached to a bigger heat sink so it tends to expand less. ¾A back-to-back bearing configuration is used to maintain stability.
14-24
Speed and Acceleration Limits • When the line of contact is not aligned with the angular acceleration vector (e.g., angular contact bearings): ¾At high speeds, gyroscopic forces cause the ball to spin. ¾At high speeds, a cooling and lubricating oil mist is often required: &Oil mist requires clean, dry (
